SURFACE-TREATED STEEL SHEET AND METHOD OF PRODUCING SAME
US20260159978A1
2026-06-11
19/121,133
2023-07-07
Smart Summary: A new type of steel sheet has been developed that does not use harmful hexavalent chromium. It features a special layer containing nickel on at least one side, along with a coating made from zirconium or titanium oxide. This design helps the steel resist staining from sulfides and improves paint adhesion. The surface of the steel sheet has a water contact angle of 50 degrees or less, meaning it can repel water effectively. Additionally, the amount of certain elements like potassium and sodium on the surface is kept low, ensuring better performance. 🚀 TL;DR
Abstract:
A surface-treated steel sheet that can be produced without the use of hexavalent chromium and that combines excellent sulfide staining resistance, paint secondary adhesion, and appearance is provided. A surface-treated steel sheet having, on at least one surface of a steel sheet, a Ni-containing layer and a coating layer disposed on the Ni-containing layer and containing at least one of Zr oxide or Ti oxide, wherein a water contact angle is 50° or less, and a total atomic ratio of K, Na, Mg, and Ca adsorbed on a surface of the steel sheet to all elements is 5.0% or less.
Inventors:
- Takashi UENO 13 🇯🇵 Chiyoda-ku, Tokyo, Japan
- Yusuke Nakagawa 11 🇯🇵 Chiyoda-ku, Tokyo, Japan
Assignee:
- JFE Steel Corporation 764 🇯🇵 Chiyoda-ku, TOKYO, Japan
Applicant:
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Classification:
C25D3/12 » CPC main
Electroplating: Baths therefor from solutions of nickel or cobalt
C25D3/562 » CPC further
Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
C25D5/36 » CPC further
Electroplating characterised by the process; Pretreatment or after-treatment of workpieces; Pretreatment of metallic surfaces to be electroplated of iron or steel
C25D5/50 » CPC further
Electroplating characterised by the process; Pretreatment or after-treatment of workpieces; After-treatment of electroplated surfaces by heat-treatment
C25D9/10 » CPC further
Electrolytic coating other than with metals with inorganic materials by cathodic processes on iron or steel
C25D3/56 IPC
Electroplating: Baths therefor from solutions of alloys
Description
TECHNICAL FIELD
The present disclosure relates to a surface-treated steel sheet, in particular, a surface-treated steel sheet with excellent sulfide staining resistance after painting, adhesion to the paint layer in wet environments, and appearance. The surface-treated steel sheet of the present disclosure can be suitably used in containers such as cans. The present disclosure also relates to a method of producing the surface-treated steel sheet.
BACKGROUND
A Sn plating steel sheet (tinplate), one type of surface-treated steel sheet, is widely used as material for various metal cans such as beverage cans, food cans, pails, and 18-liter cans because of its excellent corrosion resistance, weldability, workability, bright and beautiful appearance, and ease of production.
Surface-treated steel sheets used for these applications are required to have excellent adhesion to paint along with excellent resistance (sulfide staining resistance) to discoloration (sulfide staining) caused by the reaction between sulfur and Sn from the can contents (especially protein). Therefore, it is common for Sn plating steel sheets to be subjected to chromating treatment to improve the paint adhesion property and sulfide staining resistance.
Chromating treatment is one type of surface treatment using a coating solution containing a chromium compound, such as chromic acid or chromate. Typically, as the chromate treatment, a metal Cr layer and an Cr oxide layer are formed on the surface of the steel sheet by cathodic electrolysis in an electrolytic solution containing a hexavalent chromium compound, as described in Patent Literature (PTL) 1 to 3.
However, in recent years, increasing environmental awareness has led to a worldwide trend toward regulating the use of hexavalent chromium. Demand therefore exists for establishing a production method that does not use chromium in the field of surface-treated steel sheets used for containers and the like.
For example, in PTL 4, a surface-treated steel sheet with a coating containing a zirconium compound on the surface of a Sn plating steel sheet is proposed.
Another method of producing a surface-treated steel sheet without the use of hexavalent chromium is the use of trivalent chromium. For example, PTL 5 proposes a method of forming a surface treatment layer composed of a metal Cr layer and a Cr oxide layer on the surface of a Sn plating steel sheet by performing cathodic electrolysis in an electrolytic solution containing trivalent chromium ions.
CITATION LIST
Patent Literature
-
- PTL 1: JP S58-110695 A
- PTL 2: JP S55-134197 A
- PTL 3: JP S57-035699 A
- PTL 4: JP 2018-135569 A
- PTL 5: JP 7070823 B
SUMMARY
Technical Problem
However, the above-described conventional technology has the following problems.
For example, the surface-treated steel sheet proposed in PTL 4 can be formed without performing chromate treatment. According to PTL 4, the surface-treated steel sheet has excellent sulfide staining resistance and paint layer adhesion.
However, in PTL 4, the paint layer adhesion was evaluated under mild conditions compared to the actual environment of a can. In reality, the surface-treated steel sheet proposed in PTL 4 has insufficient adhesion to paint (hereinafter referred to as “paint secondary adhesion” (coating secondary adhesion)) in wet environments, which represent more severe conditions.
According to the method proposed in PTL 5, a surface treatment layer can be formed without using hexavalent chromium. According to PTL 5, the surface-treated steel sheet obtained by the above method has excellent paint secondary adhesion and sulfide staining resistance under severe conditions similar to the actual environment of a can.
However, the surface-treated steel sheet produced by the method proposed in PTL 5 has a poor appearance because the original bright and beautiful metallic luster of the tinplate is lost.
Thus, a surface-treated steel sheet that can be produced without the use of hexavalent chromium and that combines excellent sulfide staining resistance, paint secondary adhesion, and appearance has yet to be realized.
It is an aim of the present disclosure, conceived in light of the above circumstances, to provide a surface-treated steel sheet that can be produced without using hexavalent chromium and that has excellent sulfide staining resistance, paint secondary adhesion, and appearance.
Solution to Problem
As a result of intensive studies to achieve to above aim, we made the following discoveries (1) and (2).
-
- (1) In a surface-treated steel sheet having a coating layer containing at least one of Zr oxide and Ti oxide on a Ni-containing layer, controlling each of the water contact angle and the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface of the steel sheet to all elements each to be within a specific range makes it possible to obtain a surface-treated steel sheet that has excellent sulfide staining resistance, paint secondary adhesion, and appearance.
- (2) The aforementioned surface-treated steel sheet can be produced by performing surface conditioning under a predetermined set of conditions after coating formation, followed by a final water washing using water whose electrical conductivity is equal to or less than a predetermined value.
The present disclosure has been made based on these discoveries. We provide the following.
-
- 1. A surface-treated steel sheet including, on at least one side of a steel sheet,
- a Ni-containing layer; and
- a coating layer disposed on the Ni-containing layer and containing at least one of Zr oxide and Ti oxide, wherein
- a water contact angle is 50° or less, and
- a total atomic ratio of K, Na, Mg, and Ca adsorbed on a surface of the steel sheet to all elements is 5.0% or less.
- 2. The surface-treated steel sheet according to 1, wherein the Ni-containing layer has a Ni coating weight of 0.1 g/m2 to 20.0 g/m2 per side of the steel sheet.
- 3. The surface-treated steel sheet according to 1 or 2, wherein a total coating weight of Zr oxide and Ti oxide in the coating layer is 0.3 mg/m2 to 50.0 mg/m2 per side of the steel sheet in terms of amount of metal Zr and amount of metal Ti.
- 4. The surface-treated steel sheet according to any one of 1 to 3, wherein the coating layer further contains P, and a P coating weight is 50.0 mg/m2 or less per side of the steel sheet.
- 5. The surface-treated steel sheet according to any one of 1 to 4, wherein the coating layer further contains Mn, and a Mn coating weight is 50.0 mg/m2 or less per side of the steel sheet.
- 6. A method of producing a surface-treated steel sheet including, on at least one side of a steel sheet, a Ni-containing layer, and a coating layer disposed on the Ni-containing layer and containing at least one of Zr oxide and Ti oxide, the method including:
- a coating formation process of treating a surface of a steel sheet having a Ni-containing layer on at least one side with an aqueous solution containing at least one of Zr ions and Ti ions to form the coating layer on the Ni-containing layer;
- a surface conditioning process of holding the aqueous solution at over 30.0 g/m2 to 60.0 g/m2 or less on a surface of the coating layer for 0.1 seconds to 20.0 seconds; and
- a water washing process of subjecting the steel sheet after the surface conditioning process to water washing at least once, wherein
- in the water washing process,
- water with an electrical conductivity of 100 μS/m or less is used at least in the last water washing.
Advantageous Effect
According to the present disclosure, a surface-treated steel sheet that uses no hexavalent chromium and that combines excellent sulfide staining resistance, paint secondary adhesion, and appearance can be provided. The surface-treated steel sheet of the present disclosure can be suitably used as a material for containers and the like.
DETAILED DESCRIPTION
A method for carrying out the presently disclosed techniques will be described in detail below. The following description merely presents examples of preferred embodiments of the present disclosure, and the present disclosure is not limited to these embodiments.
A surface-treated steel sheet in an embodiment of the present disclosure includes, on at least one side of the steel sheet, a Ni-containing layer and a coating layer disposed on the Ni-containing layer, the coating layer containing at least one of Zr oxide and Ti oxide. In the present disclosure, it is important that the water contact angle be 50° or less, and that the total atomic ratio of K, Na, Mg, and Ca adsorbed on a surface of the steel sheet to all elements be 5.0% or less. The following is a description of each of the above constituent elements of the surface-treated steel sheet.
[Steel Sheet]
Any steel sheet can be used as the above steel sheet without any particular limitation, but a steel sheet for cans is preferred. For example, an ultra low carbon steel sheet or low carbon steel sheet can be used as the steel sheet. The method of producing the steel sheet is not limited, and a steel sheet produced by any method may be used, but it typically suffices to use a cold-rolled steel sheet. The cold-rolled steel sheet can be produced by general production processes, for example, hot rolling, pickling, cold rolling, annealing, and temper rolling.
The chemical composition of the steel sheet is not limited, but the steel sheet may contain C, Mn, Cr, P, S, Si, Cu, Ni, Mo, Al, and unavoidable impurities to the extent that the effects of the scope of the present disclosure are not impaired. In this case, a steel sheet with the chemical composition specified in ASTM A623M-09, for example, can be suitably used as the steel sheet.
In one embodiment of the present disclosure, a steel sheet having a chemical composition containing, in mass %,
-
- C: 0.0001% to 0.13%,
- Si: 0% to 0.020%,
- Mn: 0.01% to 0.60%,
- P: 0% to 0.020%,
- S: 0% to 0.030%,
- Al: 0% to 0.20%,
- N: 0% to 0.040%,
- Cu: 0% to 0.20%,
- Ni: 0% to 0.15%,
- Cr: 0% to 0.10%,
- Mo: 0% to 0.05%,
- Ti: 0% to 0.020%,
- Nb: 0% to 0.020%,
- B: 0% to 0.020%,
- Ca: 0% to 0.020%,
- Sn: 0% to 0.020%, and
- Sb: 0% to 0.020%,
- with the balance being Fe and inevitable impurities, is preferably used. In the aforementioned chemical composition, Si, P, S, Al, and N are components whose content is more preferable the lower it is, and Cu, Ni, Cr, Mo, Ti, Nb, B, Ca, Sn, and Sb are components that can optionally be added.
No lower limit is placed on the thickness of the steel sheet, but the thickness is preferably 0.10 mm or more. No upper limit is placed on the thickness of the steel sheet either, but the thickness is preferably 0.60 mm or less. The term “steel sheet” as used here includes a “steel strip”.
[Ni-Containing Layer]
The Ni-containing layer need only be provided on at least one side of the steel sheet but may be provided on both sides. The Ni-containing layer need only cover at least a portion of the steel sheet but may cover the entire side on which the Ni-containing layer is provided. The Ni-containing layer may be a continuous layer or a discontinuous layer. The discontinuous layer is, for example, a layer with an island-like structure.
As the Ni-containing layer, any layer that contains nickel can be used. For example, one or both of a Ni layer and a Ni alloy layer can be used. For example, the case of a Ni alloy layer resulting from diffusion annealing treatment after Ni plating is also considered a Ni alloy layer. The Ni alloy layer is, for example, a Ni—Fe alloy layer.
The Ni-containing layer is preferably a Ni-based plating layer. Here, the “Ni-based plating layer” is defined as a plating layer with a Ni content of 50 mass % or more. In other words, the Ni-based plating layer is a Ni plating layer or a plating layer consisting of Ni-based alloy.
The Ni-based plating layer may be a dispersion plating layer (composite plating layer) in which solid fine particles are dispersed in Ni or a Ni-based alloy as a matrix. As the solid fine particles, fine particles with any material property can be used without any limitation. The fine particles may be either inorganic fine particles or organic fine particles. The organic fine particles include, for example, fine particles made of resin. Any resin can be used as the resin, but fluororesin is preferably used, and polytetrafluoroethylene (PTFE) is more preferably used. As the inorganic fine particles, fine particles made of any inorganic material can be used without any limitation. The inorganic material may, for example, be a metal (including alloys), a compound, or other single substance. Among these, fine particles including at least one selected from the group consisting of oxides, nitrides, and carbides are preferably used, and fine particles of metal oxides are preferably used. Examples of the metal oxides include aluminum oxide, chromium oxide, titanium oxide, and zinc oxide.
The particle size of the fine particles used in the dispersion plating is not limited, and particles of any size can be used. However, the diameter of the fine particles preferably does not exceed the thickness of the dispersion plating layer as the Ni-containing layer. Typically, the diameter of the fine particles is preferably 1 nm or more, more preferably 10 nm or more. The diameter of the fine particles is preferably 50 μm or less, more preferably 1000 nm or less.
The Ni coating weight in the Ni-containing layer is not limited and can be any amount. However, from the perspective of further improving the appearance and corrosion resistance of the surface-treated steel sheet, the Ni coating weight is preferably set to 20.0 g/m2 or less per side of the steel sheet. From the same perspective, the Ni coating weight is preferably set to 0.1 g/m2 or more and more preferably to 0.2 g/m2 or more. From the perspective of further improving workability, the Ni coating weight is even more preferably set to 1.0 g/m2 or more.
The Ni coating weight of the Ni-containing layer is measured by a calibration curve method using X-ray fluorescence. First, a plurality of steel sheets with known Ni coating weight are prepared, the X-ray fluorescence intensity derived from Ni is measured for the plates in advance, and the relationship between the measured X-ray fluorescence intensity and the Ni coating weight is linearly approximated to yield a calibration curve. The X-ray fluorescence intensity derived from Ni in the surface-treated steel sheet can then be measured, and the above-described calibration curve can be used to determine the Ni coating weight of the Ni-containing layer.
The method of forming the Ni-containing layer is not limited, and any method, such as electroplating, can be used. In the case of forming a Ni—Fe alloy layer as a Ni-containing layer, the Ni—Fe alloy layer can be formed by forming a Ni layer on the steel sheet surface, by electroplating or another such method, and then annealing.
The surface side of the Ni-containing layer may contain Ni oxide or may contain no Ni oxide at all. However, from the perspective of further improving the paint secondary adhesion and sulfide staining resistance, the surface side of the Ni-containing layer preferably does not contain Ni oxide. Although Ni oxide can be formed by dissolved oxygen contained in water used in water washing after Ni plating, the Ni oxide contained in the Ni-containing layer is preferably removed by the below-described pretreatment or the like.
[Coating Layer]
A coating layer containing at least one of Zr oxide and Ti oxide exists on the Ni-containing layer. The inclusion of at least one of Zr oxide and Ti oxide in the coating layer is necessary to obtain excellent sulfide staining resistance, paint secondary adhesion, and appearance.
No lower limit is placed on the total coating weight of Zr oxide and Ti oxide in the coating layer. However, from the perspective of further improving sulfide staining resistance, the total coating weight of the Zr oxide and Ti oxide is preferably 0.3 mg/m2 or more, more preferably 0.4 mg/m2 or more, and even more preferably 0.5 mg/m2 or more, per side of the steel sheet in terms of the amount of metal Zr and amount of metal Ti. No upper limit is placed on the total coating weight of Zr oxide and Ti oxide in the coating layer either. However, if the total coating weight of Zr oxide and Ti oxide is excessively high, the appearance may be impaired and the paint secondary adhesion may be compromised due to cohesion failure of the coating layer. Therefore, from the perspective of ensuring more stable paint secondary adhesion, the total coating weight of the Zr oxide and Ti oxide is preferably 50.0 mg/m2 or less, more preferably 45.0 mg/m2 or less, and even more preferably 40.0 mg/m2 or less, per side of the steel sheet in terms of the amount of metal Zr and amount of metal Ti. In calculating the total coating weight of Zr oxide and Ti oxide, the value yielded by conversion to the amount of metal Zr is used as the coating weight of Zr oxide, and the value yielded by conversion to the amount of metal Ti is used as the coating weight of Ti oxide.
The coating weight of Zr oxide in the coating layer is measured by a calibration curve method using X-ray fluorescence. First, a plurality of steel sheets with known Zr coating weight are prepared, the X-ray fluorescence intensity derived from Zr is measured for the plates in advance, and the relationship between the measured X-ray fluorescence intensity and the coating weight as metal Zr is linearly approximated to yield a calibration curve. The X-ray fluorescence intensity derived from Zr in the surface-treated steel sheet can then be measured, and the above-described calibration curve can be used to determine the coating weight of Zr oxide in the coating layer in terms of metal Zr.
The coating weight of Ti oxide in the coating layer is also measured by a calibration curve method using X-ray fluorescence. First, a plurality of steel sheets with known Ti coating weight are prepared, the X-ray fluorescence intensity derived from Ti is measured for the plates in advance, and the relationship between the measured X-ray fluorescence intensity and the coating weight as metal Ti is linearly approximated to yield a calibration curve. The X-ray fluorescence intensity derived from Ti in the surface-treated steel sheet can then be measured, and the above-described calibration curve can be used to determine the coating weight of Ti oxide in the coating layer in terms of metal Ti.
The coating layer may contain P from the perspective of further improving sulfide staining resistance. Although no upper limit is placed on the coating weight of P contained in the coating layer, the coating weight of P is preferably 50.0 mg/m2 or less per side of the steel sheet, since paint secondary adhesion may be impaired due to cohesion failure of the coating layer. No lower limit is placed on the coating weight of P in the coating layer, and the coating weight of P may, for example, be 0.0 mg/m2, i.e., no P whatsoever may be contained.
The coating weight of P in the coating layer is measured by a calibration curve method using X-ray fluorescence. First, a plurality of steel sheets with known P coating weight are prepared, the X-ray fluorescence intensity derived from P is measured for the plates in advance, and the relationship between the measured X-ray fluorescence intensity and the P coating weight is linearly approximated to yield a calibration curve. The X-ray fluorescence intensity derived from P in the surface-treated steel sheet can then be measured, and the above-described calibration curve can be used to determine the coating weight of P in the coating layer.
The coating layer may contain Mn from the perspective of further improving sulfide staining resistance. Although no upper limit is placed on the coating weight of Mn contained in the coating layer, the coating weight of Mn is preferably 50.0 mg/m2 or less per side of the steel sheet, since paint secondary adhesion may be impaired due to cohesion failure of the coating layer. No lower limit is placed on the coating weight of Mn in the coating layer, and the coating weight of Mn may, for example, be 0.0 mg/m2, i.e., no Mn whatsoever may be contained.
The coating weight of Mn in the coating layer is measured by a calibration curve method using X-ray fluorescence. First, a plurality of steel sheets with known Mn coating weight are prepared, the X-ray fluorescence intensity derived from Mn is measured for the plates in advance, and the relationship between the measured X-ray fluorescence intensity and the Mn coating weight is linearly approximated to yield a calibration curve. The X-ray fluorescence intensity derived from Mn in the surface-treated steel sheet can then be measured, and the above-described calibration curve can be used to determine the coating weight of Mn in the coating layer.
The aforementioned coating layer may contain Ni. No upper limit is placed on the Ni content in the coating layer. The coating layer need not contain Ni, i.e., the content may be 0.0 mg/m2.
The aforementioned coating layer may contain C. No upper limit is placed on the C content in the coating layer. The coating layer need not contain C, i.e., the content may be 0.0 mg/m2.
The aforementioned coating layer may contain elements other than Zr, Ti, O, Ni, Mn, P and C, along with the below-described K, Na, Mg, and Ca. Elements other than those described above include metallic impurities such as Cu, Zn, and Fe, and elements such as S, N, F, Cl, Br, and Si, contained in the aqueous solution used in the coating formation process described below. However, an excessive presence of elements other than Zr, Ti, O, Ni, Mn, P, C, K, Na, Mg, and Ca may reduce sulfide staining resistance or adhesion. Therefore, the total content of elements other than Zr, Ti, O, Ni, Mn, P, C, K, Na, Mg, and Ca in the coating layer is preferably 30% or less, and more preferably 20% or less, in atomic ratio. The coating layer need not contain elements other than Zr, Ti, O, Ni, Mn, P, C, K, Na, Mg, and Ca, i.e., the content may be 0% in atomic ratio. The content of the above elements can be measured by XPS (X-ray photoelectron spectroscopy).
[Water Contact Angle]
In the present disclosure, it is important that the water contact angle on the surface-treated steel sheet be 50° or less. By highly hydrophilizing the surface of the surface-treated steel sheet so that the water contact angle is 50° or less, firm hydrogen bonds are formed between the resin in the paint and the surface-treated steel sheet, resulting in high adhesion even in wet environments. From the perspective of further improving paint secondary adhesion, the water contact angle is preferably set to 48° or less, and even more preferably to 45° or less. No lower limit is placed on the water contact angle, and the water contact angle may be 0°, because a lower contact angle is preferable from the perspective of improving adhesion. However, from the perspective of ease of production and the like, the water contact angle may be 5° or more, or 8° or more.
Furthermore, the surface of the surface-treated steel sheet in the present disclosure, i.e., the surface of the coating layer containing at least one of Zr oxide and Ti oxide, is stable with regard to heat. For example, the water contact angle does not change significantly after heat treatment equivalent to paint baking. It is assumed that such thermal stability of the surface state also contributes to improved adhesion. Therefore, the water contact angle on the surface-treated steel sheet after heat treatment equivalent to painting is also preferably 50° or less, more preferably 48° or less, and even more preferably 45° or less. No lower limit is placed on the water contact angle of the surface-treated steel sheet after heat treatment equivalent to painting, and the water contact angle may be 0°, but the water contact angle may be 5° or more, or 8° or more. The conditions of the heat treatment equivalent to painting are set to a maximum temperature of 200° C. and a holding time at the maximum temperature of 10 minutes.
Although the mechanism by which the surface of the surface-treated steel sheet becomes hydrophilic is not clear, it is believed that a high degree of hydrophilicity is imparted by adjustment of the surface micro-roughness in the surface conditioning process described below. In a case in which the surface conditioning process described below is not performed, the surface of the surface-treated steel sheet cannot be fixed in a hydrophilic state, and the water contact angle exceeds 50°, even if the surface is hydrophilic immediately after production.
The water contact angle can be measured by the θ/2 method. In the measurement, the temperature of the surface-treated steel sheet to be measured is set to 20° C., and distilled water at a temperature of 20° C. is dropped onto the surface of the surface-treated steel sheet. The contact angle after 1 second from dropping is calculated by the θ/2 method. More specifically, measurement can be made by the method described in the Examples. Here, the surface of the surface-treated steel sheet may be coated with an anti-rust oil such as CSO (Cottonseed Oil), DOS (Dioctyl Sebacate), and ATBC (Acetyl Tributyl Citrate). In a case in which the surface-treated steel sheet is painted with oil, the water contact angle measured by the method described in the Examples after vaporizing the painted oil by the heat treatment equivalent to painting is taken as the water contact angle of the surface-treated steel sheet after painting with oil. As described above, the surface-treated steel sheet of the present disclosure is stable with respect to heat treatment. Therefore, if the water contact angle measured after the aforementioned heat treatment and the atomic ratio of the adsorbed elements described below satisfy the conditions of the present disclosure, the surface-treated steel sheet before the aforementioned heat treatment is also considered to achieve the effects of the present disclosure. Although additives such as rust inhibitors contained in the painted oil may remain on the surface of the surface-treated steel sheet after heat treatment equivalent to painting, the amount thereof is so small that it does not affect the above-described water contact angle and atomic ratio of adsorbed elements.
In a surface-treated steel sheet produced using a conventional hexavalent chromium bath as proposed in PTL 1 to 3, it has been reported that the composition of the chromium hydrated oxide layer on the surface layer significantly affects the adhesion to paint or film in wet environments. In wet environments, water that has penetrated the paint layer or film inhibits adhesion at the interface between the paint layer or film and the chromium hydrated oxide layer. It was thus believed that when numerous OH groups, which are hydrophilic, are present in the chromium hydrated oxide layer, expansion of moisture from water at the interface is promoted, resulting in reduced adhesive strength. In a conventional surface-treated steel sheet, reducing the number of OH groups through the progression of oxidation of chromium hydrated oxide, i.e., making the surface hydrophobic, therefore improves adhesion to paint or film in wet environments.
In contrast, in the present disclosure, a high degree of hydrophilicity is developed by the action of the minute irregularities on the surface of the coating layer formed in the surface conditioning process described below, allowing a paint to penetrate into the fine irregularities and form firm mechanical bonds at the interface between the paint layer and the surface treated steel sheet by the anchor effect, thereby maintaining high adhesion even under wet conditions.
[Atomic Ratio of Adsorbed Elements]
As described above, the surface-treated steel sheet of the present disclosure has high hydrophilicity, with a water contact angle of 50° or less, and the surface is chemically active. Therefore, cations of elements such as K, Na, Mg, and Ca are easily adsorbed on the surface of the surface-treated steel sheet. We discovered that simply setting the water contact angle to 50° or less does not achieve the intended adhesion, due to the effect of the adsorbed cations. By reducing the amount of the cations adsorbed on the surface of the surface-treated steel sheet, the present disclosure improves adhesion to the resin and achieves excellent paint secondary adhesion, while also exhibiting firm barrier properties against sulfur penetration, thus achieving excellent sulfide staining resistance.
Specifically, the total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet to all elements is 5.0% or less, preferably 3.0% or less, and more preferably 1.0% or less. The lower the total atomic ratio, the better; hence, no lower limit is established, and the total atomic ratio may be 0.0%. The total atomic ratio can be measured by XPS. In the measurement, it suffices to determine the atomic ratios of K, Na, Mg, and Ca to all elements from the integrated intensity of the narrow spectra of K2p, Na1s, Ca2p, and Mg1s at the top surface of the surface-treated steel sheet, using the relative sensitivity factor method. More specifically, measurement can be made by the method described in the Examples. In a case in which the surface-treated steel sheet is painted with oil, the atomic ratio measured by the method described in the Examples after vaporizing the painted oil by the heat treatment equivalent to painting is taken as the atomic ratio of the elements adsorbed to the surface-treated steel sheet after painting with oil.
[Production Method]
In the method of producing a surface-treated steel sheet in an embodiment of the present disclosure, a surface-treated steel sheet with the aforementioned characteristics can be produced by the method described below.
A method of producing a surface-treated steel sheet in an embodiment of the present disclosure is a method of producing a surface-treated steel sheet that includes, on at least one side of the steel sheet, a Ni-containing layer and a coating layer disposed on the Ni-containing layer, and the method includes the following processes (1) to (3). Each process is described below.
-
- (1) Coating formation process
- (2) Surface conditioning process
- (3) Water washing process
[Coating Formation Process]
In the aforementioned coating formation process, the surface of a steel sheet having a Ni-containing layer on at least one side is treated with an aqueous solution containing at least one of Zr ions and Ti ions to form a coating layer on the Ni-containing layer. The formed coating layer is a coating layer containing at least one of Zr oxide and Ti oxide.
The treatment with an aqueous solution is not limited and may be performed by any method. The treatment can, for example, be performed by electrolysis. In a case in which the treatment is performed by electrolysis, the steel sheet with the Ni-containing layer is preferably subjected to cathodic electrolysis in the aqueous solution. Conventional equipment used for chromating treatment or the like can be used as is for the cathodic electrolysis. Therefore, from the perspective of equipment cost reduction, the coating layer is preferably formed by cathodic electrolysis.
The method of preparing the aqueous solution is not limited. For example, the aqueous solution can be prepared by dissolving one or both of a Zr-containing compound as a Zr ion source and a Ti-containing compound as a Ti ion source in water. Distilled water or deionized water can be used as the water, but these examples are not limiting, and any water can be used.
Any compounds that can provide Zr ions and Ti ions can be used as the Zr-containing compound and Ti-containing compound, respectively. For example, Zr salts such as ZrF4 or Zr complexes such as H2ZrF6 and K2ZrF6 are preferably used as the Zr-containing compound. As the pH rises on the cathode surface, Zr ions become Zr oxide and form a coating. For example, Ti salts such as TiF4 or Ti complexes such as H2TiF6 and K2TiF6 are preferably used as the Ti-containing compound. As the pH rises on the cathode surface, Ti ions become Ti oxide and form a coating.
The aqueous solution may further contain at least one selected from the group consisting of fluorine ions, nitrate ions, ammonium ions, phosphate ions, Mn ions, and sulfate ions. In a case in which the aqueous solution contains both nitrate ions and ammonium ions, the treatment can be performed in a short time, from several seconds to several tens of seconds, which is extremely advantageous from an industrial standpoint. The aqueous solution therefore preferably contains both nitrate ions and ammonium ions in addition to at least one of Zr ions and Ti ions. Hereafter, the unit of ionic concentration “ppm” refers to parts per million unless otherwise specified.
In a case in which the aqueous solution contains Zr ions, no lower limit is placed on the concentration of the Zr ions, but the concentration is preferably set to 100 ppm or more. No upper limit is placed on the concentration of the Zr ions either, but the concentration is preferably set to 4000 ppm or less. Similarly, in a case in which the aqueous solution contains Ti ions, no lower limit is placed on the concentration of the Ti ions, but the concentration is preferably set to 100 ppm or more. No upper limit is placed on the concentration of the Ti ions either, but the concentration is preferably set to 4000 ppm or less.
In a case in which the aqueous solution contains fluorine ions, no lower limit is placed on the concentration of the fluorine ions, but the concentration is preferably set to 120 ppm or more. No upper limit is placed on the concentration of the fluorine ions either, but the concentration is preferably set to 4000 ppm or less. In a case in which the aqueous solution contains phosphate ions, no lower limit is placed on the concentration of the phosphate ions, but the concentration is preferably set to 50 ppm or more. No upper limit is placed on the concentration of the phosphate ions either, but the concentration is preferably set to 5000 ppm or less. In a case in which the aqueous solution contains Mn ions, no lower limit is placed on the concentration of the Mn ions, but the concentration is preferably set to 50 ppm or more. No upper limit is placed on the concentration of the Mn ions either, but the concentration is preferably set to 5000 ppm or less. In a case in which the aqueous solution contains ammonium ions, no lower limit is placed on the concentration of the ammonium ions, and the concentration may be 0 ppm. No upper limit is placed on the concentration of the ammonium ions either, but the concentration is preferably set to 20000 ppm or less. In a case in which the aqueous solution contains nitrate ions, no lower limit is placed on the concentration of the nitrate ions, and the concentration may be 0 ppm. No upper limit is placed on the concentration of the nitrate ions either, but the concentration is preferably set to 20000 ppm or less. In a case in which the aqueous solution contains sulfate ions, no lower limit is placed on the concentration of the sulfate ions, and the concentration may be 0 ppm. No upper limit is placed on the concentration of the sulfate ions either, but the concentration is preferably set to 20000 ppm or less.
No upper limit is placed on the temperature of the aqueous solution during cathodic electrolysis, but the temperature is preferably set to 50° C. or lower, for example. Cathodic electrolysis at temperatures of 50° C. or lower enables the formation of a dense, uniform coating microstructure constituted by very fine particles. By setting the temperature of the aqueous solution to 50° C. or lower, the occurrence of defects, cracks, microcracks, and the like in the coating layer to be formed can be suppressed, and the paint layer adhesion can be further improved. No lower limit is placed on the temperature of the aqueous solution during cathodic electrolysis either, but the temperature is preferably set to 10° C. or higher, for example. By setting the temperature of the aqueous solution to 10° C. or higher, the efficiency of coating formation can be increased. In addition, if the temperature of the aqueous solution is 10° C. or higher, cooling of the solution is not necessary even when the outside temperature is high, such as during the summer, which is economical.
No lower limit is placed on the pH of the aqueous solution, but the pH is preferably set to 3 or higher. If the pH is 3 or higher, the formation efficiency of Zr oxide or Ti oxide can be further improved. No upper limit is placed on the pH of the aqueous solution either, but the pH is preferably set to 5 or less. A pH of 5 or less prevents the formation of large amounts of precipitation in the aqueous solution and can achieve good continuous productivity.
Nitric acid, ammonia water, or the like, for example, may be added to the aqueous solution for the purpose of adjusting pH and improving electrolytic efficiency.
No lower limit is placed on the current density for cathodic electrolysis, but the current density is, for example, preferably set to 0.05 A/dm2 or higher, more preferably 1 A/dm2 or higher. If the current density is 0.05 A/dm2 or higher, the formation efficiency of Zr oxide or Ti oxide is improved. As a result, a more stable coating layer containing Zr oxide or Ti oxide can be generated, further improving sulfide staining resistance and anti-yellowing property. No upper limit is placed on the current density during cathodic electrolysis, but the current density is, for example, preferably set to 50 A/dm2 or less, more preferably 10 A/dm2 or less. If the current density is 50 A/dm2 or less, the efficiency of generating Zr oxides or Ti oxides can be made appropriate, and the generation of coarse Zr oxide or Ti oxide with poor adhesion can be suppressed.
No limit is placed on the electrolysis time in the aforementioned cathodic electrolysis, and it suffices to adjust the electrolysis time according to the current density to obtain the Zr coating weight and Ti coating weight described above.
The current pattern in the aforementioned cathodic electrolysis may be continuous current passage or intermittent current passage. The relationship between the aqueous solution and the steel sheet during the aforementioned cathodic electrolysis is not limited, and the solution may be relatively stationary or moving. However, from the perspective of promoting the reaction and improving uniformity, cathodic electrolysis is preferably conducted while the steel sheet and the aqueous solution are moved relative to each other. For example, cathodic electrolysis can be performed continuously while passing a steel sheet through a treatment tank housing an aqueous solution containing at least one of Zr ions and Ti ions, so that the steel sheet and the aqueous solution are moved relative to each other.
When cathodic electrolysis is performed while moving the steel sheet and the aqueous solution relative to each other, the relative flow speed between the aqueous solution and the steel sheet is preferably 50 m/min or more. If the relative flow speed is 50 m/min or more, the pH of the steel sheet surface where hydrogen is generated together with current passage can be made more uniform, effectively suppressing the formation of coarse Zr oxide or Ti oxide. No upper limit is placed on the relative flow speed.
[Surface Conditioning Process]
Next, surface conditioning is performed on the coating layer obtained in the coating formation process. Specifically, the aqueous solution is held at over 30.0 g/m2 to 60.0 g/m2 or less on a surface of the coating layer for 0.1 seconds to 20.0 seconds. By performing surface conditioning under the above conditions, the coating layer can be fixed in a highly hydrophilic state.
The mechanism by which the surface conditioning process can fix the coating layer in a highly hydrophilic state is not clear but is thought to be as follows. By bringing the coating layer into contact with the aqueous solution, the surface of the coating layer is slightly etched, forming minute irregularities on the surface of the coating layer. The action of these minute irregularities results in a high degree of hydrophilicity. This hydrophilicity is different from the hydrophilicity resulting from the presence of hydrophilic functional groups, such as OH groups, and is due to the physical structure provided by the surface roughness, which also has excellent stability with respect to heat.
Although the state of existence of the aqueous solution on the surface of the coating layer is not limited, the aqueous solution is preferably in the form of a liquid film from the perspective of ensuring uniform progress of etching.
Amount of Aqueous Solution: Over 30.0 g/m2 to 60.0 g/m2 or Less
If the amount of aqueous solution used for surface conditioning is 30.0 g/m2 or less, etching does not proceed sufficiently, resulting in a water contact angle that is greater than 50°. The amount of the aqueous solution is therefore set to over 30.0 g/m2, preferably 32.0 g/m2 or more, and more preferably 35.0 g/m2 or more. On the other hand, if the amount of aqueous solution exceeds 60.0 g/m2, etching in fact does not proceed and the desired hydrophilicity cannot be obtained. This is thought to be because the progress of etching depends on the amount of dissolved oxygen present near the interface between the coating layer and the aqueous solution. In other words, if the amount of aqueous solution is excessive, the thickness of the layer formed by the aqueous solution increases, causing an insufficient supply of oxygen to the interface, which results in insufficient progress of etching. The amount of the aqueous solution is therefore set to 60.0 g/m2 or less, preferably 58.0 g/m2 or less, and more preferably 55.0 g/m2 or less.
-
- Holding time: 0.1 seconds to 20.0 seconds
If the holding time in the surface conditioning is less than 0.1 seconds, etching does not proceed sufficiently, resulting in a water contact angle that is greater than 50°. The holding time is therefore set to 0.1 seconds or longer, preferably 0.2 seconds or longer, and more preferably 0.3 seconds or longer. On the other hand, the water contact angle is also greater than 50° in a case in which the holding time exceeds 20.0 seconds. This is thought to be due to excessive etching, leading to deviation from surface conditions suitable for the development of hydrophilicity. The holding time is therefore set to 20.0 seconds or shorter, preferably 18.0 seconds or shorter, and more preferably 15.0 seconds or shorter.
The amount of the aforementioned aqueous solution can be measured by a moisture meter using a filter-type infrared absorption method. Specifically, the absorbance at the surface is measured by a moisture meter using a filter-type infrared absorption method, and the amount of aqueous solution is determined from the absorbance using a previously determined calibration curve. The calibration curve can be prepared by the following procedures. First, a steel sheet with the above coating layer is placed on an electronic balance. The aqueous solution is dropped by pipette onto the steel sheet having the coating layer to form a liquid film over the entire surface of the steel sheet having the coating layer. The weight of the aqueous solution present on the steel sheet having the coating layer is determined from the weight of the steel sheet having the coating layer before the aqueous solution is dropped and the weight of the steel sheet having the coating layer after the aqueous solution is dropped. The resulting weight of the aqueous solution is divided by the area of the steel sheet having the coating layer to obtain the amount of aqueous solution per unit area. At the same time, the absorbance on the surface of the steel sheet having the coating layer is measured by a moisture meter using a filter-type infrared absorption method. The above measurements are performed multiple times while varying the amount of aqueous solution, and a calibration curve representing the correlation between the amount of aqueous solution and absorbance is created. A linear approximation of the correlation between the amount of aqueous solution and absorbance can be used as the calibration curve.
The method of adjusting the amount of aqueous solution present on the surface of the coating layer is not limited, and any method can be used. For example, the amount of the aqueous solution on the surface of the steel sheet can be adjusted by wringing out the solution with a wringer roll or by wiping.
Prior to the coating formation process, the steel sheet having a Ni-containing layer can optionally be pretreated. The pretreatment can, for example, remove a natural oxide film present on the surface of the Ni-containing layer. By removal of the natural oxide film, the amount of Ni oxide can be adjusted and the surface can be activated.
The method used for the pretreatment is not limited, and any method may be used. For example, pickling can be performed as the pretreatment. The pickling is not limited and can be performed by any method. The type of pickling treatment solution used for the pickling is not limited but is preferably an aqueous sulfuric acid solution such as dilute sulfuric acid. Here, the aqueous sulfuric acid solution refers to an aqueous solution of sulfuric acid and comprises the case in which components other than sulfuric acid are included. No lower limit is placed on the concentration of sulfate ions contained in the aqueous sulfuric acid solution, but the concentration is preferably 3 g/L or higher, more preferably 5 g/L or higher. No upper limit is placed on the concentration of sulfate ions contained in the aqueous sulfuric acid solution, but the concentration is preferably 200 g/L or lower, more preferably 150 g/L or lower. No lower limit is placed on the temperature of the aqueous sulfuric acid solution, but the temperature is preferably 10° C. or higher, more preferably 15° C. or higher. No upper limit is placed on the temperature of the aqueous sulfuric acid solution, but the temperature is preferably 70° C. or lower, more preferably 60° C. or lower.
After the pretreatment, water washing is preferably performed from the perspective of removing any pretreatment solution adhering to the surface.
When forming the Ni-containing layer on the surface of the base steel sheet, pretreatment is preferably performed on the base steel sheet. Although any of the above pretreatments can be performed, at least one of degreasing, pickling, and water washing is preferably performed.
Degreasing removes rolling oil, anti-rust oil, and the like from the steel sheet. The degreasing is not limited and can be performed by any method. After degreasing, water washing is preferably performed to remove any degreasing treatment solution adhering to the steel sheet surface.
Pickling removes the natural oxide film present on the surface of the steel sheet and activates the surface. The pickling is not limited and can be performed by any method. After pickling, water washing is preferably performed to remove any pickling treatment solution adhering to the steel sheet surface.
[Water Washing Process]
Next, the steel sheet after the surface conditioning process is subjected to water washing at least once. Water washing removes any residual aqueous solution from the surface of the steel sheet. The water washing is not limited and may be performed by any method. For example, a water washing tank can be installed downstream from the tank for coating formation, and the steel sheet after the coating formation process can be continuously immersed in water. Water washing may also be performed by spraying water on the steel sheet after the coating formation process.
The number of times the water washing is performed is not limited and may be one or more. However, to avoid an excessively large number of water washing tanks, the number of times water washing is performed is preferably five or less. In the case of performing water washing treatment two or more times, each water washing may be performed in the same or a different manner.
In the present disclosure, it is important to use water with an electrical conductivity of 100 μS/m or less at least in the last water washing of the water washing process. This reduces the amount of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet and thereby improves adhesion. Water with an electrical conductivity of 100 μS/m or less can be produced by any method. The water with an electrical conductivity of 100 μS/m or less may, for example, be reverse osmosis water, ion-exchanged water, or distilled water. The electrical conductivity of the water used for water washing can be measured using a conductivity meter.
When water washing is performed two or more times in the water washing process, any water can be used for the water washing other than the last water washing, since the above-described effect can be obtained by using water with an electrical conductivity of 100 μS/m or less for the last water washing. Water with an electrical conductivity of 100 μS/m or less may also be used for water washing other than the last water washing. However, from the perspective of cost reduction, water with an electrical conductivity of 100 μS/m or less is preferably used only for the last water washing, with normal water such as tap water or industrial water being used for water washing other than the last water washing.
From the perspective of further reducing the amount of K, Na, Mg, and Ca adsorbed on the surface of surface-treated steel sheet, the electrical conductivity of the water used for the last water washing is preferably set to 50 μS/m or less, more preferably 30 μS/m or less. On the other hand, no lower limit is placed on the electrical conductivity, and the electrical conductivity may be 0 μS/m. However, from the perspective of cost reduction, the electrical conductivity is preferably set to 1 μS/m or more.
The temperature of water used for the water washing treatment is not limited and may be any temperature. However, since excessively high temperatures place an excessive burden on the water washing equipment, the temperature of the water used for water washing is preferably set to 95° C. or lower. No lower limit is placed on the temperature of water used for water washing either, but the temperature is preferably 0° C. or higher. The temperature of the water used in the water washing may be room temperature.
No limit is placed on the water washing time per water washing treatment, but from the perspective of increasing the effectiveness of the water washing treatment, the water washing time is preferably 0.1 seconds or longer, more preferably 0.2 seconds or longer. No upper limit is placed on the water washing time per water washing treatment either, but in the case of production on a continuous line, the water washing time is preferably 10 seconds or less, more preferably 8 seconds or less, because a longer water washing time reduces the line speed and lowers productivity.
Drying may optionally be performed after the water washing process. The drying method is not limited, and ordinary dryers or electric furnace drying methods, for example, can be applied. The temperature during the drying process is preferably 100° C. or lower. Within the aforementioned range, the transformation of the surface-treatment coating can be suppressed. Although no lower limit is placed on the temperature, the lower limit is typically around room temperature.
Applications of the surface-treated steel sheet of the present disclosure are not limited, but the surface-treated steel sheet is particularly suitable as a surface-treated steel sheet for containers used in the production of various types of containers, such as food cans, beverage cans, pails, and 18-liter cans, for example.
Examples
To determine the effects of the present disclosure, surface-treated steel sheets were produced by the following procedures, and their properties were evaluated. The present disclosure is not, however, limited to the following examples.
(Formation of Ni-Containing Layer)
First, steel sheets were sequentially subjected to electrolytic degreasing, water washing, pickling by immersion in dilute sulfuric acid, and water washing. The steel sheets were then subjected to Ni electroplating to obtain Ni plating steel sheets with a Ni plating layer as a Ni-containing layer on both sides of the steel sheet. The Ni coating weight of the Ni-containing layer was set at this time to the values illustrated in Tables 2 and 3 by changing the current passage time. The Ni coating weight of the Ni-containing layer was measured by the above-described calibration curve method using X-ray fluorescence. In some Examples, a Ni—Fe alloy layer was formed as the Ni-containing layer. That is, after forming the Ni plating layer by the above-described method, a Ni—Fe alloy layer was formed by annealing.
A steel sheet for cans (T4 blank sheet) with a thickness of 0.17 mm was used as the steel sheet.
(Pretreatment for Steel Sheets with Ni-Containing Layer Formed Thereon)
The resulting steel sheets with a Ni-containing layer formed thereon were then subjected to pickling by immersion in dilute sulfuric acid and water washing sequentially as illustrated in Tables 2 and 3. For comparison, no pretreatment was performed on some of the Examples.
(Coating Formation Process)
Next, the surface of the pretreated steel sheet with the Ni-containing layer formed thereon was treated with an aqueous solution to form a coating layer on the Ni-containing layer. Specifically, an aqueous solution with the composition illustrated in Table 1 was used as the aqueous solution, and the coating layer was formed by performing cathodic electrolysis in the aqueous solution. The temperature of the aqueous solution was set to 35° C., and the pH was adjusted to be between 3 and 5. The Zr coating weight and Ti coating weight were controlled by adjusting the electrical density. Zirconium fluoride (ZrF4) was used as the Zr-containing compound and titanium fluoride (TiF4) as the Ti-containing compound. The aqueous solution was prepared by adjusting the concentration of each ion through use of additional compounds other than the Zr-containing compound and the Ti-containing compound for the aqueous solution to have the compositions illustrated in Table 1.
(Surface Conditioning Process)
After the coating formation process, surface conditioning was performed under the set of conditions illustrated in Tables 2 and 3. Specifically, at the end of the coating formation process, the steel sheet having the aqueous solution adhering to its surface was squeezed with a wringer roll to adjust the amount of aqueous solution present on the surface of the coating layer to the amounts listed in Tables 2 and 3. The amount of aqueous solution was measured by a moisture meter using a filter-type infrared absorption method, as described above. The steel sheets were then held for the holding time illustrated in Tables 2 and 3. In other words, the aqueous solution used in the surface conditioning process is the same as that used in the aforementioned coating formation process.
(Water Washing Process)
Next, water washing treatment was applied to the steel sheets after the aforementioned surface preparation process. The water washing treatment was performed 1 to 5 times under the set of conditions illustrated in Tables 2 and 3. The method of each water washing and the electrical conductivity of the water used are illustrated in Tables 2 and 3. For the times when the water washing method was “immersion”, water washing was performed by immersing the steel sheet in water. For the times when the water washing method was “spray”, on the other hand, water washing was performed by spraying water onto the steel sheet. The electrical conductivity was measured using a conductivity meter.
The coating weight of Zr oxide, the coating weight of Ti oxide, the P coating weight, and the Mn coating weight in the coating layer were measured for each of the obtained surface-treated steel sheets. The measurements were performed by the above-described calibration curve method using X-ray fluorescence. The measurement results are listed in Tables 4 and 5. In Tables 4 and 5, the coating weight for Zr oxide and Ti oxide are listed as the amount of metal Zr and amount of metal Ti, respectively.
The water contact angle and the atomic ratios of adsorbed elements were measured by the following procedures for each of the obtained surface-treated steel sheets. The measurement results are listed in Tables 4 and 5.
(Water Contact Angle)
The water contact angle was measured using an automatic contact angle meter, model CA-VP, produced by Kyowa Interface Science Co., Ltd. The surface temperature of the surface treated steel sheet was 20° C.±1° C., and distilled water at 20° C.±1° C. was used. A 2 μl drop of distilled water was dropped onto the surface of the surface-treated steel sheet, and the contact angle was measured 1 second later by the θ/2 method. The arithmetic mean value of the contact angles of 5 drops was used as the water contact angle.
To confirm the change in contact angle due to heat, the contact angle was also measured after the surface-treated steel sheet was subjected to heat treatment at 200° C. for 10 minutes. The measurement conditions were the same as above. As a result, the contact angle values were substantially the same before and after heat treatment for the surface-treated steel sheets meeting the conditions of the present disclosure. In contrast, some of the surface-treated steel sheets that did not meet the conditions of the present disclosure exhibited significant changes in contact angle values due to heat treatment.
(Atomic Ratio of Adsorbed Elements)
The total atomic ratio of K, Na, Mg, and Ca adsorbed on the surface of the surface-treated steel sheet to all elements was measured by XPS. No sputtering was performed in the measurements. From the integrated intensity of the narrow spectra of K2p, Na1s, Ca2p, and Mg1s at the top surface of the sample, the detected atomic ratios to all elements were quantified using the relative sensitivity factor method and calculated as (K atomic ratio+Na atomic ratio+Ca atomic ratio+Mg atomic ratio). For the XPS measurement, the scanning X-ray photoelectron spectrometer PHI X-tool, produced by ULVAC-PHI, was used, with the X-ray source being a monochrome AlKα beam, the voltage being 15 kV, the beam diameter being 100 μm φ, and the take-off angle being 45°.
Furthermore, the obtained surface-treated steel sheets were evaluated for sulfide staining resistance, paint secondary adhesion, and appearance by the following methods. The evaluation results are listed in Tables 4 and 5.
(Sulfide Staining Resistance)
On the surface of a surface-treated steel sheet prepared by the above-described method, a commercial epoxy resin paint for cans was applied at a dry mass of 60 mg/dm2, subsequently baked at 200° C. for 10 minutes, and then left at room temperature for 24 hours. The resulting steel sheet was then cut to a predetermined size. An aqueous solution containing anhydrous disodium hydrogen phosphate: 7.1 g/L, anhydrous sodium dihydrogen phosphate: 3.0 g/L, and L-cysteine hydrochloride: 6.0 g/L was prepared and boiled for 1 hour, after which the reduction in volume by evaporation was compensated for by adding pure water. The resulting aqueous solution was poured into a pressure-resistant, heat-resistant container made of Teflon® (Teflon is a registered trademark in Japan, other countries, or both). The steel sheet cut to the predetermined size was immersed in the aqueous solution, and the lid of the container was closed and sealed. The sealed container was subjected to retort treatment at a temperature of 131° C. for 60 minutes.
The sulfide staining resistance was evaluated based on the appearance of the steel sheet after the retort treatment. No change whatsoever in the appearance before and after the test was evaluated as “1”, the occurrence of blackening in 10% by area or less was evaluated as “2”, the occurrence of blackening in 20% or less by area and more than 10% by area was evaluated as “3”, and the occurrence of blackening in more than 20% by area was evaluated as “4”. A rating of 1 to 3 indicates excellent sulfide staining resistance in practical use and was thus considered passing.
(Paint Secondary Adhesion)
The surface of the resulting surface-treated steel sheet was coated with an epoxy phenolic paint and baked at 210° C. for 10 minutes to produce a prepainted steel sheet. The coating weight of the paint was 50 mg/dm2.
Two prepainted steel sheets made under the same conditions were stacked so that the coated surfaces faced each other with a nylon adhesive film therebetween and were then pressure bonded under a set of conditions including a pressure of 2.94×105 Pa, a temperature of 190° C., and a pressure bonding time of 30 seconds. The bonded steel sheets were then divided into 5 mm wide test pieces. The divided test pieces were immersed for 168 hours in a 55° C. test solution consisting of a mixed aqueous solution containing 1.5 mass % citric acid and 1.5 mass % common salt. After immersion and subsequent washing and drying, the two steel sheets of the divided test pieces were pulled apart in a tensile tester, and the tensile strength at the time of separation was measured. The average of three test pieces was evaluated at the following four levels. For practical purposes, a result of 1 to 3 can be evaluated as excellent paint secondary adhesion.
-
- 1: 2.5 kgf or more
- 2: 2.0 kgf or more but less than 2.5 kgf
- 3: 1.5 kgf or more but less than 2.0 kgf
- 4: Less than 1.5 kgf
(Appearance)
The L-value was measured for surface-treated steel sheets prepared by the above-described method and for steel sheets before the coating formation process. The L value was measured using the spectrophotometer SQ-2000 produced by Nippon Denshoku Industries, with a measurement diameter of 30 mm φ, and the SCI (Specular Component Include: including positive reflection) value was used. The difference in L-value, ΔL, was then calculated using the formula (L-value of steel sheet before coating formation process)−(L-value of resulting surface-treated steel sheet). The L value represents the brightness of the color, and a larger ΔL represents greater degradation in appearance. ΔL was evaluated at the following four levels. For practical purposes, a result of 1 to 3 can be evaluated as excellent in appearance.
-
- 1: Less than 1.0
- 2: 1.0 or more but less than 3.0
- 3: 3.0 or more but less than 5.0
- 4: 5.0 or more
As is clear from Tables 4 and 5, all of the surface-treated steel sheets that met the conditions of the present disclosure combined excellent sulfide staining resistance, paint secondary adhesion, and appearance.
| TABLE 1 | |
| Aqueous | Composition (ppm) |
| solution | Zr4+ | Ti4+ | Mn4+ | PO43− | F− | NO33− | NH4+ |
| A | 3000 | — | — | — | 4000 | — | — |
| B | 1500 | — | — | — | 2000 | 3000 | 2000 |
| C | 2000 | — | — | 950 | 2000 | 1600 | 1000 |
| D | 2000 | — | — | 950 | 2000 | 7000 | 2500 |
| E | 2000 | 2000 | — | 950 | 2000 | 7000 | 2500 |
| F | — | 1500 | — | — | 2000 | 3000 | 2000 |
| G | — | 2000 | — | 950 | 2000 | 1600 | 1000 |
| H | — | 2000 | — | 950 | 2000 | 7000 | 2500 |
| I | 2000 | 2000 | 2000 | 950 | 2000 | 7000 | 2500 |
| TABLE 2 | |
| Production conditions |
| Surface conditioning |
| Ni-containing layer | Coating | process | Water washing treatment |
| Ni | formation | Amount of | First time | Second time |
| coating | process | aqueous | Electrical | Electrical | ||||||
| weight | Aqueous | solution | Holding | conductivity | conductivity | |||||
| No. | Type | [g/m2] | Pretreatment | solution | [g/m2] | time [sec] | Method | [μS/m] | Method | [μS/m] |
| 1 | Ni | 15.3 | pickling | A | 38.5 | 0.8 | immersion | 21 | — | — |
| 2 | Ni | 1.2 | none | B | 43.2 | 11.2 | spray | 17 | — | — |
| 3 | Ni | 5.3 | pickling | C | 48.3 | 2.3 | spray | 100 | immersion | 15 |
| 4 | Ni | 0.5 | none | D | 31.3 | 6.5 | spray | 61 | spray | 12 |
| 5 | Ni | 0.2 | pickling | E | 51.9 | 1.8 | spray | 9 | immersion | 30 |
| 6 | Ni | 0.6 | none | F | 37.5 | 0.5 | immersion | 15 | immersion | 6 |
| 7 | Ni | 0.9 | pickling | G | 40.3 | 13.8 | spray | 98 | immersion | 43 |
| 8 | Ni | 2.5 | none | H | 41.3 | 2.6 | immersion | 12 | immersion | 59 |
| 9 | Ni | 3.3 | pickling | I | 41.8 | 7.2 | immersion | 21 | immersion | 213 |
| 10 | Ni | 8.2 | none | A | 42.0 | 13.6 | immersion | 121 | spray | 63 |
| 11 | Ni | 0.3 | pickling | B | 53.9 | 8.0 | immersion | 14 | immersion | 194 |
| 12 | Ni | 0.7 | none | C | 47.4 | 13.2 | immersion | 73 | spray | 101 |
| 13 | Ni | 2.1 | pickling | D | 45.0 | 5.3 | immersion | 118 | immersion | 76 |
| 14 | Ni | 1.4 | none | E | 37.4 | 4.5 | immersion | 123 | spray | 63 |
| 15 | Ni | 1.9 | pickling | F | 39.5 | 11.5 | immersion | 67 | immersion | 40 |
| 16 | Ni | 0.8 | none | G | 49.5 | 9.9 | immersion | 31 | immersion | 94 |
| 17 | Ni | 0.5 | pickling | H | 51.8 | 4.1 | immersion | 19 | immersion | 51 |
| 18 | Ni | 1.0 | none | I | 38.6 | 2.3 | immersion | 21 | immersion | 14 |
| 19 | Ni | 1.5 | pickling | A | 37.7 | 1.0 | immersion | 13 | immersion | 171 |
| 20 | Ni | 0.8 | none | B | 45.3 | 2.6 | spray | 29 | immersion | 36 |
| 21 | Ni | 0.8 | pickling | D | 41.6 | 8.7 | immersion | 20 | immersion | 69 |
| 22 | Ni | 0.8 | none | E | 48.9 | 5.6 | immersion | 16 | spray | 225 |
| 23 | Ni | 0.8 | pickling | H | 46.5 | 11.3 | immersion | 32 | immersion | 52 |
| 24 | Ni | 0.8 | none | I | 53.0 | 8.2 | immersion | 15 | immersion | 43 |
| 25 | Ni | 0.8 | pickling | C | 46.5 | 3.2 | immersion | 13 | immersion | 16 |
| 26 | Ni | 0.8 | none | D | 49.2 | 0.7 | immersion | 15 | immersion | 32 |
| 27 | Ni | 0.8 | pickling | G | 38.3 | 2.8 | immersion | 26 | immersion | 39 |
| 28 | Ni | 0.8 | none | H | 52.4 | 0.8 | immersion | 53 | immersion | 151 |
| 29 | Ni | 0.8 | pickling | H | 39.5 | 2.8 | immersion | 24 | immersion | 16 |
| 30 | Ni | 0.8 | none | I | 46.3 | 11.2 | immersion | 86 | immersion | 22 |
| 31 | Ni | 0.8 | pickling | B | 52.6 | 13.2 | immersion | 16 | immersion | 151 |
| 32 | Ni | 0.8 | none | C | 41.6 | 11.2 | immersion | 20 | immersion | 13 |
| 33 | Ni | 0.8 | pickling | D | 56.2 | 8.9 | immersion | 9 | immersion | 136 |
| Production conditions | |||
| Water washing treatment |
| Third time | Fourth time | Fifth time |
| Electrical | Electrical | Electrical | ||||||
| conductivity | conductivity | conductivity | ||||||
| No. | Method | [μS/m] | Method | [μS/m] | Method | [μS/m] | Notes | |
| 1 | — | — | — | — | — | — | Example | |
| 2 | — | — | — | — | — | — | Example | |
| 3 | — | — | — | — | — | — | Example | |
| 4 | — | — | — | — | — | — | Example | |
| 5 | immersion | 15 | — | — | — | — | Example | |
| 6 | spray | 8 | — | — | — | — | Example | |
| 7 | immersion | 106 | immersion | 27 | — | — | Example | |
| 8 | spray | 262 | spray | 9 | — | — | Example | |
| 9 | immersion | 103 | immersion | 31 | immersion | 13 | Example | |
| 10 | spray | 25 | immersion | 191 | spray | 18 | Example | |
| 11 | spray | 15 | — | — | — | — | Example | |
| 12 | spray | 22 | — | — | — | — | Example | |
| 13 | immersion | 17 | — | — | — | — | Example | |
| 14 | spray | 29 | — | — | — | — | Example | |
| 15 | spray | 13 | — | — | — | — | Example | |
| 16 | immersion | 8 | — | — | — | — | Example | |
| 17 | spray | 24 | — | — | — | — | Example | |
| 18 | immersion | 19 | — | — | — | — | Example | |
| 19 | spray | 18 | — | — | — | — | Example | |
| 20 | immersion | 6 | — | — | — | — | Example | |
| 21 | spray | 13 | — | — | — | — | Example | |
| 22 | immersion | 28 | — | — | — | — | Example | |
| 23 | spray | 16 | — | — | — | — | Example | |
| 24 | immersion | 24 | — | — | — | — | Example | |
| 25 | spray | 21 | — | — | — | — | Example | |
| 26 | immersion | 26 | — | — | — | — | Example | |
| 27 | spray | 26 | — | — | — | — | Example | |
| 28 | immersion | 15 | — | — | — | — | Example | |
| 29 | spray | 14 | — | — | — | — | Example | |
| 30 | spray | 13 | — | — | — | — | Example | |
| 31 | spray | 17 | — | — | — | — | Example | |
| 32 | spray | 20 | — | — | — | — | Example | |
| 33 | spray | 11 | — | — | — | — | Example | |
| TABLE 3 | |
| Production conditions |
| Surface conditioning |
| Ni-containing layer | Coating | process | Water washing treatment |
| Ni | formation | Amount of | First time | Second time |
| coating | process | aqueous | Electrical | Electrical | ||||||
| weight | Aqueous | solution | Holding | conductivity | conductivity | |||||
| No. | Type | [g/m2] | Pretreatment | solution | [g/m2] | time [sec] | Method | [μS/m] | Method | [μS/m] |
| 34 | Ni | 0.8 | none | E | 59.3 | 6.8 | immersion | 21 | immersion | 209 |
| 35 | Ni | 0.8 | pickling | F | 63.0 | 7.8 | immersion | 106 | immersion | 168 |
| 36 | Ni | 0.8 | none | G | 33.6 | 4.5 | immersion | 89 | immersion | 13 |
| 37 | Ni | 0.8 | pickling | H | 30.8 | 1.5 | immersion | 154 | immersion | 22 |
| 38 | Ni | 0.8 | none | I | 29.2 | 0.9 | immersion | 135 | immersion | 9 |
| 39 | Ni | 0.8 | pickling | A | 40.3 | 16.1 | immersion | 101 | immersion | 14 |
| 40 | Ni | 0.8 | none | B | 37.2 | 19.4 | immersion | 116 | immersion | 69 |
| 41 | Ni | 0.8 | pickling | C | 36.5 | 20.8 | immersion | 132 | immersion | 89 |
| 42 | Ni | 0.8 | none | D | 38.6 | 0.2 | immersion | 16 | immersion | 163 |
| 43 | Ni | 0.8 | pickling | E | 42.3 | 0.1 | immersion | 19 | immersion | 117 |
| 44 | Ni | 0.8 | none | F | 52.9 | 0.05 | immersion | 109 | immersion | 105 |
| 45 | Ni | 0.8 | pickling | G | 39.3 | 11.3 | spray | 43 | — | — |
| 46 | Ni | 0.8 | none | H | 40.6 | 13.5 | immersion | 83 | — | — |
| 47 | Ni | 0.8 | pickling | I | 37.2 | 10.0 | immersion | 151 | — | — |
| 48 | Ni | 0.8 | none | A | 52.2 | 2.5 | immersion | 105 | immersion | 36 |
| 49 | Ni | 0.8 | pickling | B | 53.6 | 3.3 | immersion | 11 | spray | 78 |
| 50 | Ni | 0.8 | none | C | 50.9 | 12.1 | immersion | 9 | immersion | 205 |
| 51 | Ni | 0.8 | pickling | D | 43.2 | 7.4 | immersion | 106 | immersion | 132 |
| 52 | Ni | 0.8 | none | E | 48.5 | 5.0 | immersion | 13 | immersion | 16 |
| 53 | Ni | 0.8 | pickling | F | 44.4 | 1.5 | immersion | 21 | immersion | 9 |
| 54 | Ni | 0.8 | none | G | 39.5 | 1.6 | immersion | 38 | immersion | 153 |
| 55 | Ni | 0.8 | pickling | H | 36.1 | 2.6 | immersion | 109 | immersion | 12 |
| 56 | Ni | 0.8 | none | I | 42.1 | 7.9 | immersion | 12 | immersion | 165 |
| 57 | Ni | 0.8 | pickling | A | 49.2 | 10.5 | immersion | 13 | immersion | 80 |
| 58 | Ni | 0.8 | none | B | 44.1 | 11.5 | immersion | 119 | immersion | 74 |
| 59 | Ni | 0.8 | pickling | C | 52.3 | 1.9 | immersion | 125 | immersion | 39 |
| 60 | Ni—Fe | 0.8 | none | D | 39.3 | 2.6 | immersion | 19 | immersion | 34 |
| 61 | Ni—Fe | 0.8 | pickling | E | 45.1 | 3.4 | immersion | 22 | immersion | 46 |
| 62 | Ni—Fe | 0.8 | none | F | 36.5 | 0.9 | immersion | 20 | immersion | 20 |
| 63 | Ni—Fe | 0.8 | pickling | G | 48.9 | 6.6 | immersion | 89 | immersion | 13 |
| 64 | Ni—Fe | 0.8 | none | H | 51.8 | 8.9 | immersion | 30 | immersion | 67 |
| 65 | Ni—Fe | 0.8 | pickling | I | 40.9 | 5.3 | immersion | 25 | immersion | 54 |
| Production conditions | |||
| Water washing treatment |
| Third time | Fourth time | Fifth time |
| Electrical | Electrical | Electrical | ||||||
| conductivity | conductivity | conductivity | ||||||
| No. | Method | [μS/m] | Method | [μS/m] | Method | [μS/m] | Notes | |
| 34 | spray | 18 | — | — | — | — | Example | |
| 35 | spray | 13 | — | — | — | — | Comparative | |
| example | ||||||||
| 36 | spray | 16 | — | — | — | — | Example | |
| 37 | spray | 18 | — | — | — | — | Example | |
| 38 | spray | 6 | — | — | — | — | Comparative | |
| example | ||||||||
| 39 | spray | 25 | — | — | — | — | Example | |
| 40 | spray | 11 | — | — | — | — | Example | |
| 41 | spray | 10 | — | — | — | — | Comparative | |
| example | ||||||||
| 42 | spray | 29 | — | — | — | — | Example | |
| 43 | spray | 20 | — | — | — | — | Example | |
| 44 | spray | 13 | — | — | — | — | Comparative | |
| example | ||||||||
| 45 | — | — | — | — | — | — | Example | |
| 46 | — | — | — | — | — | — | Example | |
| 47 | — | — | — | — | — | — | Comparative | |
| example | ||||||||
| 48 | — | — | — | — | — | — | Example | |
| 49 | — | — | — | — | — | — | Example | |
| 50 | — | — | — | — | — | — | Comparative | |
| example | ||||||||
| 51 | spray | 47 | — | — | — | — | Example | |
| 52 | immersion | 68 | — | — | — | — | Example | |
| 53 | spray | 112 | — | — | — | — | Comparative | |
| example | ||||||||
| 54 | spray | 22 | immersion | 40 | — | — | Example | |
| 55 | immersion | 105 | spray | 53 | — | — | Example | |
| 56 | spray | 13 | immersion | 101 | — | — | Comparative | |
| example | ||||||||
| 57 | spray | 199 | immersion | 103 | spray | 38 | Example | |
| 58 | immersion | 106 | immersion | 79 | immersion | 93 | Example | |
| 59 | spray | 51 | immersion | 83 | spray | 261 | Comparative | |
| example | ||||||||
| 60 | spray | 23 | — | — | — | — | Example | |
| 61 | spray | 15 | — | — | — | — | Example | |
| 62 | spray | 11 | — | — | — | — | Example | |
| 63 | spray | 19 | — | — | — | — | Example | |
| 64 | spray | 10 | — | — | — | — | Example | |
| 65 | spray | 18 | — | — | — | — | Example | |
| TABLE 4 | ||
| Measurement results |
| Coating layer | Atomic |
| Zr oxide and Ti oxide | ratio of | Evaluation |
| Zr coating | Ti coating | P coating | Mn coating | Water | adsorbed | Sulfide | Paint | ||||
| weight | weight | Total | weight | weight | contact | elements | staining | secondary | |||
| No. | [mg/m2] | [mg/m2] | [mg/m2] | [mg/m2] | [mg/m2] | angle [°] | [%] | resistance | adhesion | Appearance | Notes |
| 1 | 5.8 | 0.0 | 5.8 | 0.0 | 0.0 | 22.3 | 0.3 | 1 | 1 | 1 | Example |
| 2 | 3.2 | 0.0 | 3.2 | 0.0 | 0.0 | 42.3 | 0.0 | 1 | 1 | 1 | Example |
| 3 | 16.3 | 0.0 | 16.3 | 22.1 | 0.0 | 33.1 | 0.0 | 1 | 1 | 1 | Example |
| 4 | 7.8 | 0.0 | 7.8 | 10.3 | 0.0 | 9.3 | 0.0 | 1 | 1 | 1 | Example |
| 5 | 11.5 | 3.2 | 14.7 | 8.6 | 0.0 | 6.8 | 0.0 | 1 | 1 | 1 | Example |
| 6 | 0.0 | 15.6 | 15.6 | 0.0 | 0.0 | 13.5 | 0.0 | 1 | 1 | 1 | Example |
| 7 | 0.0 | 2.8 | 2.8 | 33.9 | 0.0 | 11.3 | 0.0 | 1 | 1 | 1 | Example |
| 8 | 0.0 | 13.5 | 13.5 | 47.3 | 0.0 | 17.3 | 0.0 | 1 | 1 | 1 | Example |
| 9 | 9.3 | 1.2 | 10.5 | 8.2 | 12.3 | 11.3 | 0.5 | 1 | 1 | 1 | Example |
| 10 | 2.1 | 0.0 | 2.1 | 0.0 | 0.0 | 22.5 | 0.2 | 1 | 1 | 1 | Example |
| 11 | 15.3 | 0.0 | 15.3 | 0.0 | 0.0 | 36.3 | 0.0 | 1 | 1 | 1 | Example |
| 12 | 32.5 | 0.0 | 32.5 | 13.8 | 0.0 | 7.6 | 0.7 | 1 | 1 | 1 | Example |
| 13 | 39.4 | 0.0 | 39.4 | 3.7 | 0.0 | 41.9 | 0.1 | 1 | 1 | 1 | Example |
| 14 | 12.5 | 11.3 | 23.8 | 9.3 | 0.0 | 30.3 | 0.0 | 1 | 1 | 1 | Example |
| 15 | 0.0 | 20.4 | 20.4 | 0.0 | 0.0 | 18.3 | 0.0 | 1 | 1 | 1 | Example |
| 16 | 0.0 | 16.8 | 16.8 | 28.5 | 0.0 | 20.6 | 0.0 | 1 | 1 | 1 | Example |
| 17 | 0.0 | 25.6 | 25.6 | 16.7 | 0.0 | 44.5 | 0.0 | 1 | 1 | 1 | Example |
| 18 | 6.9 | 0.8 | 7.7 | 12.6 | 32.1 | 39.6 | 0.0 | 1 | 1 | 1 | Example |
| 19 | 13.6 | 0.0 | 13.6 | 0.0 | 0.0 | 13.2 | 0.0 | 1 | 1 | 1 | Example |
| 20 | 22.9 | 0.0 | 22.9 | 0.0 | 0.0 | 22.5 | 0.0 | 1 | 1 | 1 | Example |
| 21 | 7.6 | 0.0 | 7.6 | 16.8 | 0.0 | 13.5 | 0.2 | 1 | 1 | 1 | Example |
| 22 | 4.8 | 3.7 | 8.5 | 17.2 | 0.0 | 24.3 | 0.0 | 1 | 1 | 1 | Example |
| 23 | 0.0 | 12.6 | 12.6 | 0.4 | 0.0 | 32.6 | 0.0 | 1 | 1 | 1 | Example |
| 24 | 24.6 | 14.3 | 38.9 | 3.2 | 48.3 | 18.6 | 0.1 | 1 | 1 | 1 | Example |
| 25 | 13.5 | 0.0 | 13.5 | 16.3 | 0.0 | 9.8 | 0.0 | 1 | 1 | 1 | Example |
| 26 | 19.3 | 0.0 | 19.3 | 2.7 | 0.0 | 12.6 | 0.6 | 1 | 1 | 1 | Example |
| 27 | 14.6 | 0.0 | 14.6 | 12.6 | 0.0 | 10.3 | 0.1 | 1 | 1 | 1 | Example |
| 28 | 17.6 | 0.0 | 17.6 | 3.8 | 0.0 | 26.1 | 0.0 | 1 | 1 | 1 | Example |
| 29 | 0.0 | 47.9 | 47.9 | 11.3 | 0.0 | 41.5 | 0.0 | 2 | 2 | 2 | Example |
| 30 | 36.3 | 22.0 | 58.3 | 17.5 | 7.5 | 16.3 | 0.0 | 3 | 3 | 3 | Example |
| 31 | 0.3 | 0.0 | 0.3 | 0.0 | 0.0 | 25.3 | 0.0 | 2 | 2 | 1 | Example |
| 32 | 0.2 | 0.0 | 0.2 | 34.1 | 0.0 | 19.2 | 0.0 | 3 | 3 | 1 | Example |
| 33 | 3.6 | 0.0 | 3.6 | 9.1 | 0.0 | 46.2 | 0.0 | 2 | 2 | 1 | Example |
| TABLE 5 | ||
| Measurement results |
| Coating layer | Atomic |
| Zr oxide and Ti oxide | ratio of | Evaluation |
| Zr coating | Ti coating | P coating | Mn coating | Water | adsorbed | Sulfide | Paint | ||||
| weight | weight | Total | weight | weight | contact | elements | staining | secondary | |||
| No. | [mg/m2] | [mg/m2] | [mg/m2] | [mg/m2] | [mg/m2] | angle [°] | [%] | resistance | adhesion | Appearance | Notes |
| 34 | 1.2 | 34.5 | 35.7 | 22.7 | 0.0 | 48.9 | 0.0 | 3 | 3 | 1 | Example |
| 35 | 0.0 | 16.2 | 16.2 | 0.0 | 0.0 | 53.3 | 0.0 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 36 | 0.0 | 11.2 | 11.2 | 39.6 | 0.0 | 45.6 | 0.0 | 2 | 2 | 1 | Example |
| 37 | 0.0 | 4.3 | 4.3 | 11.2 | 0.0 | 49.3 | 0.2 | 3 | 3 | 1 | Example |
| 38 | 21.6 | 9.8 | 31.4 | 16.8 | 16.3 | 68.6 | 0.0 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 39 | 8.3 | 0.0 | 8.3 | 0.0 | 0.0 | 45.2 | 0.0 | 2 | 2 | 1 | Example |
| 40 | 15.5 | 0.0 | 15.5 | 0.0 | 0.0 | 48.3 | 0.0 | 3 | 3 | 1 | Example |
| 41 | 13.6 | 0.0 | 13.6 | 13.8 | 0.0 | 54.6 | 0.0 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 42 | 12.3 | 0.0 | 12.3 | 7.5 | 0.0 | 47.6 | 0.1 | 2 | 2 | 1 | Example |
| 43 | 6.3 | 4.2 | 10.5 | 5.2 | 0.0 | 49.9 | 0.0 | 3 | 3 | 1 | Example |
| 44 | 0.0 | 15.6 | 15.6 | 0.0 | 0.0 | 73.6 | 0.0 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 45 | 0.0 | 24.1 | 24.1 | 13.4 | 0.0 | 16.2 | 1.2 | 2 | 2 | 1 | Example |
| 46 | 0.0 | 16.3 | 16.3 | 12.8 | 0.0 | 13.8 | 3.6 | 3 | 3 | 1 | Example |
| 47 | 22.5 | 1.3 | 23.8 | 1.9 | 8.2 | 22.8 | 5.3 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 48 | 22.1 | 0.0 | 22.1 | 0.0 | 0.0 | 41.3 | 2.1 | 2 | 2 | 1 | Example |
| 49 | 16.2 | 0.0 | 16.2 | 0.0 | 0.0 | 31.4 | 4.6 | 3 | 3 | 1 | Example |
| 50 | 32.5 | 0.0 | 32.5 | 3.7 | 0.0 | 36.9 | 6.9 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 51 | 16.3 | 0.0 | 16.3 | 16.2 | 0.0 | 13.2 | 1.8 | 2 | 2 | 1 | Example |
| 52 | 11.2 | 26.5 | 37.7 | 17.9 | 0.0 | 8.9 | 3.3 | 3 | 3 | 1 | Example |
| 53 | 0.0 | 29.8 | 29.8 | 0.0 | 0.0 | 29.8 | 7.2 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 54 | 0.0 | 10.5 | 10.5 | 6.4 | 0.0 | 16.4 | 2.3 | 2 | 2 | 1 | Example |
| 55 | 0.0 | 12.3 | 12.3 | 4.8 | 0.0 | 11.9 | 3.9 | 3 | 3 | 1 | Example |
| 56 | 1.8 | 2.9 | 4.7 | 18.5 | 29.8 | 10.0 | 5.8 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 57 | 16.2 | 0.0 | 16.2 | 0.0 | 0.0 | 12.6 | 1.1 | 2 | 2 | 1 | Example |
| 58 | 13.2 | 0.0 | 13.2 | 0.0 | 0.0 | 38.2 | 4.3 | 3 | 3 | 1 | Example |
| 59 | 9.0 | 0.0 | 9.0 | 16.4 | 0.0 | 34.5 | 6.2 | 4 | 4 | 1 | Comparative |
| example | |||||||||||
| 60 | 6.3 | 0.0 | 6.3 | 4.2 | 0.0 | 16.3 | 0.0 | 1 | 1 | 1 | Example |
| 61 | 5.2 | 12.3 | 17.5 | 11.5 | 0.0 | 22.5 | 0.1 | 1 | 1 | 1 | Example |
| 62 | 0.0 | 7.8 | 7.8 | 0.0 | 0.0 | 43.0 | 0.0 | 1 | 1 | 1 | Example |
| 63 | 0.0 | 15.6 | 15.6 | 21.3 | 0.0 | 32.6 | 0.0 | 1 | 1 | 1 | Example |
| 64 | 0.0 | 5.1 | 5.1 | 6.8 | 0.0 | 18.7 | 0.3 | 1 | 1 | 1 | Example |
| 65 | 19.3 | 8.8 | 28.1 | 15.6 | 11.2 | 19.3 | 0.0 | 1 | 1 | 1 | Example |
Claims
1. A surface-treated steel sheet comprising, on at least one side of a steel sheet,
a Ni-containing layer; and
a coating layer disposed on the Ni-containing layer and containing at least one of Zr oxide and Ti oxide, wherein
a water contact angle is 50° or less, and
a total atomic ratio of K, Na, Mg, and Ca adsorbed on a surface of the steel sheet to all elements is 5.0% or less.
2. The surface-treated steel sheet according to claim 1, wherein the Ni-containing layer has a Ni coating weight of 0.1 g/m2 to 20.0 g/m2 per side of the steel sheet.
3. The surface-treated steel sheet according to claim 1, wherein a total coating weight of Zr oxide and Ti oxide in the coating layer is 0.3 mg/m2 to 50.0 mg/m2 per side of the steel sheet in terms of amount of metal Zr and amount of metal Ti.
4. The surface-treated steel sheet according to claim 1, wherein the coating layer further contains P, and a P coating weight is 50.0 mg/m2 or less per side of the steel sheet.
5. The surface-treated steel sheet according to claim 1, wherein the coating layer further contains Mn, and a Mn coating weight is 50.0 mg/m2 or less per side of the steel sheet.
6. A method of producing a surface-treated steel sheet comprising, on at least one side of a steel sheet, a Ni-containing layer, and a coating layer disposed on the Ni-containing layer and containing at least one of Zr oxide and Ti oxide, the method comprising:
a coating formation process of treating a surface of a steel sheet having a Ni-containing layer on at least one side with an aqueous solution containing at least one of Zr ions and Ti ions to form the coating layer on the Ni-containing layer;
a surface conditioning process of holding the aqueous solution at over 30.0 g/m2 to 60.0 g/m2 or less on a surface of the coating layer for 0.1 seconds to 20.0 seconds; and
a water washing process of subjecting the steel sheet after the surface conditioning process to water washing at least once, wherein
in the water washing process,
water with an electrical conductivity of 100 μS/m or less is used at least in the last water washing.