Sn-BASED PLATED STEEL SHEET

Abstract

To provide a Sn-based plated steel sheet capable of exhibiting superior corrosion resistance, yellowing resistance, coating film adhesiveness, and sulphide stain resistance without using a chromate film. A Sn-based plated steel sheet of the present invention includes: a steel sheet; a Sn-based plating layer located on at least one surface of the steel sheet; and a coating layer located on the Sn-based plating layer, wherein the Sn-based plating layer contains 1.0 g/m.sup.2 to 15.0 g/m.sup.2 of Sn per side in terms of metal Sn, the coating layer contains zirconium oxide, and a content of the zirconium oxide is 1.0 mg/m.sup.2 to 10.0 mg/m.sup.2 per side in terms of metal Zr, the zirconium oxide includes zirconium oxide with an amorphous structure, and a crystalline layer whose main component is zirconium oxide with a crystalline structure is present on an upper layer of the zirconium oxide with the amorphous structure.

Claims

1. A Sn-based plated steel sheet comprising: a steel sheet; a Sn-based plating layer located on at least one surface of the steel sheet; and a coating layer located on the Sn-based plating layer, wherein the Sn-based plating layer contains 1.0 g/m.sup.2 to 15.0 g/m.sup.2 of Sn per side in terms of metal Sn, the coating layer contains zirconium oxide, and a content of the zirconium oxide is 1.0 mg/m.sup.2 to 10.0 mg/m.sup.2 per side in terms of metal Zr, the zirconium oxide includes zirconium oxide with an amorphous structure, and a crystalline layer whose main component is zirconium oxide with a crystalline structure is present on an upper layer of the zirconium oxide with the amorphous structure, wherein the crystalline structure is determined when a clear diffraction spot is obtained in an electron beam diffraction pattern, and the amorphous structure is determined when a continuous ring-shaped diffraction pattern is obtained instead of the clear diffraction spot.

2. The Sn-based plated steel sheet according to claim 1, wherein the crystalline layer in the coating layer includes an uppermost surface portion of the coating layer, and the number of detected locations of the crystalline layer is at least one or more in order from the uppermost surface portion in a thickness direction, wherein the uppermost surface portion means a portion including an uppermost surface of the coating layer among each of 10 equal portions of the coating layer in the thickness direction at any position of the coating layer, and the number of detected locations of the crystalline layer means the number of locations determined to be the crystalline structure among 10 measured locations in the electron beam diffraction pattern at a center portion of the thickness direction of each portion among 10 equal portions where the coating layer is divided into 10 equal portions in the thickness direction at any position of the coating layer.

3. The Sn-based plated steel sheet according to claim 2, wherein the number of detected locations of the crystalline layer is five or less, including the uppermost surface portion of the coating layer and in order from the uppermost surface portion in the thickness direction.

Description

EXAMPLES

[0067] Next, the Sn-based plated steel sheet and the manufacturing method of the Sn-based plated steel sheet according to the present invention will be concretely explained while illustrating examples and comparative examples. Note that the following examples are merely examples of the Sn-based plated steel sheet and the manufacturing method of the Sn-based plated steel sheet according to the present invention, and the Sn-based plated steel sheet and the manufacturing method of the Sn-based plated steel sheet according to the present invention are not limited to the following examples.

Method of Producing a Test Material

[0068] A method of producing a test material will be explained. Note that later-explained test materials in examples were produced according to the method of producing the test material.

[0069] First, a low-carbon cold-rolled steel sheet with a sheet thickness of 0.2 mm was subjected to electrolytic alkali degreasing, water washing, dilute sulfuric acid immersion pickling, and water washing as pretreatments, then subjected to Sn-based electroplating using a phenolsulfonic acid bath, and then subjected to a heating and melting treatment. Through these treatments, the Sn-based plating layers were formed on both surfaces of the steel sheet that had undergone these treatments. The coating weight of the Sn-based plating layer per side by metal Sn amount was set to about 2.8 g/m.sup.2 as a standard. The coating weight of the Sn-based plating layer was adjusted by changing an energization time. Some test materials were not subjected to the above heating and melting treatment.

[0070] Next, the steel sheet on which the Sn-based plating layers were formed was immersed in cooling water with a predetermined hardness for a predetermined time. Within five seconds thereafter the plated steel sheet that had undergone the immersion treatment was subjected to the cathode electrolytic treatment in an aqueous solution containing zirconium fluoride (cathode electrolytic solution) to form a coating layer containing zirconium oxide on a surface of each Sn-based plating layer. The temperature of the cathode electrolytic solution was set to 35° C. and the pH of the cathode electrolytic solution was adjusted to be 3.0 to 5.0. The current density of the cathode electrolytic treatment and the treatment time of the cathode electrolytic treatment were adjusted according to the targeted zirconium oxide content (metal Zr amount) in the coating layer. When the cathode electrolytic treatments were performed two times, the second cathode electrolytic treatment was performed immediately after the first cathode electrolytic treatment was completed and the current density setting was changed.

[0071] The Sn-based plated steel sheets prepared in this way were subjected to various evaluations as follows.

Coating Weight of Sn-Based Plating Layer Per Side (Metal Sn Amount of Sn-Based Plating Layer)

[0072] The coating weight of the Sn-based plating layer per side (metal Sn amount of the Sn-based plating layer) was measured as follows. Several test pieces of steel sheet having the Sn-based plating layers with known metal Sn content were prepared. Next, each test piece was analyzed using an X-ray fluorescence analysis apparatus (ZSX Primus, manufactured by Rigaku Corporation) to measure X-ray fluorescence intensity derived from metal Sn in advance from a surface of the Sn-based plating layer of the test piece. Then, a calibration curve representing a relationship between the measured X-ray fluorescence intensity and the metal Sn amount was prepared. Then, the coating layer was removed from the Sn-based plated steel sheet to be a measurement object to prepare a test piece exposing the Sn-based plating layer. The X-ray fluorescence intensity derived from metal Sn was measured on the surface where the Sn-based plating layer was exposed using the X-ray fluorescence apparatus. The coating weight of the Sn-based plating layer per side (that is, the metal Sn content) was calculated by using the obtained X-ray fluorescence intensity and the calibration curve prepared in advance.

[0073] Note that measurement conditions were as follows, X-ray source: Rh, tube voltage: 50 kV, tube current: 60 mA, dispersive crystal: LiF1, and measurement diameter: 30 mm.

Investigation of Structure of Coating Layer

[0074] Samples for TEM observation were produced to investigate the structure of the coating layer by using FIB (Quata 3D FEG, manufactured by FEI Corporation), each prepared sample was subjected to observation of any field of view at an acceleration voltage of 200 kV and 100,000 magnifications by using TEM (field-emission transmission electron microscope JEM-2100F, manufactured by JEOL Ltd.), and then an electron beam diffraction pattern of the coating layer was examined at a beam diameter of 1 nm. When a continuous ring-shaped diffraction pattern was obtained instead of a clear diffraction spot in the obtained electron beam diffraction pattern, it was determined to be the amorphous structure. An amorphous structure ratio was defined as a percentage of locations determined to be the amorphous structure among 30 locations measured, which are the sum of any 10 locations in a coating thickness direction at each of three positions on the surface of the coating layer.

Amorphous structure ratio (%)=(Number of locations where amorphous structure was obtained/30)×100

[0075] When the clear diffraction spot was obtained in the electron beam diffraction pattern, it was determined to be the crystalline structure. When the crystalline structure was found on a surface layer side of the coating layer at all of any three positions, it was determined that the crystalline layer formed of the zirconium oxide with the crystalline structure is present on an upper layer of the zirconium oxide with the amorphous structure.

[0076] At each of any three positions of the coating layer, the coating layer was divided into 10 equal portions in the thickness direction, and the number of locations determined to be the crystalline structure among measured 10 locations was checked in the electron diffraction pattern at a center portion of the thickness direction of each portion among 10 equal portions. A maximum value of the number of detected locations at the three positions was defined as the number of detected locations of the crystalline layer.

Content of Zirconium Oxide (Metal Zr Amount) in Coating Layer

[0077] The content of the zirconium oxide (metal Zr amount) in the coating layer was measured according to the measurement method of the coating weight of the Sn-based plating layer per side (metal Sn amount in the Sn-based plating layer). In short, a test piece of the Sn-based plated steel sheet, which is a measurement object, is prepared. A surface of the coating layer of the test piece is subjected to measurement of X-ray fluorescence intensity derived from metal Zr by using the X-ray fluorescence analysis apparatus (ZSX Primus, manufactured by Rigaku Corporation). The obtained X-ray fluorescence intensity and the calibration curve regarding metal Zr prepared in advance were used to calculate the content of the zirconium oxide (metal Zr amount) in the coating layer.

Surface Color Tone (Yellowing) and Yellowing Over Time

[0078] A surface color tone (yellowing) was determined by a b* value using SC-GV5, manufactured by Suga Test Instruments Co., Ltd., which is a commercially available colorimeter. Measurement conditions for b* were light source: C, total reflection, and measurement diameter: 30 mm. The yellowing over time was evaluated by performing a humidity cabinet test of placing a test material of the Sn-based plated steel sheet in a thermo-hygrostat kept at 40° C. and relative humidity of 80% for four weeks and finding a change amount Δb* of the color difference b* value before and after the humidity cabinet test.

[0079] When Δb* was 1 or less, the evaluation was “A”, when it was more than 1 and 2 or less, the evaluation was “B”, when it was more than 2 and 3 or less, the evaluation was “C”, and when it was more than 3, the evaluation was “NG”. The evaluations “A”, “B”, and “C” were regarded as being acceptable.

Coating Film Adhesiveness

[0080] The coating film adhesiveness was evaluated as follows.

[0081] The test material of the Sn-based plated steel sheet was subjected to the humidity cabinet test by the method described in [Yellowing resistance], and then 7 g/m.sup.2 on a dry mass basis of a commercially available epoxy resin coating for can was applied to its surface, baked at 200° C. for 10 minutes, and placed at room temperature for 24 hours. Then, flaws reaching the steel sheet surface were formed in a grid form on the obtained Sn-based plated steel sheet (7 flaws in each of vertical and horizontal directions at an interval of 3 mm), and the portion was subjected to a tape peel test using a commercially available adhesive tape for evaluation.

[0082] When there was no peeling of the coating film at the tape stuck portion at all, the evaluation was “A”, when there was peeling of the coating film around the flaws in the grid form, the evaluation was “B”, and when there was peeling of the coating film in squares of the grid form, the evaluation was “NG”. The evaluations “A” and “B” were regarded as being acceptable.

Sulphide Stain Resistance

[0083] The sulphide stain resistance was evaluated as follows.

[0084] After 7 g/m.sup.2 on a dry mass basis of the commercially available epoxy resin coating for can was applied to the surface of the test material of the Sn-based plated steel sheet produced and subjected to the humidity cabinet test according to the method described in the above [Coating film adhesiveness], the test material was baked at 200° C. for 10 minutes and placed at room temperature for 24 hours. Then, the obtained Sn-based plated steel sheet was cut into a predetermined size and immersed in an aqueous solution composed of 0.3% of sodium dihydrogen phosphate, 0.7% of sodium hydrogenphosphate, and 0.6% of L-cysteine hydrochloride, subjected to a retort treatment at 121° C. for 60 minutes in a sealed container and evaluated from an external appearance after the test.

[0085] When there was no change in the external appearance at all before and after the test, the evaluation was “AA”, when there was slight blackening (5% or less), the evaluation was “A”, when there was blackening in a region of more than 5% and 10% or less, the evaluation was “B”, and when there was blackening in a region of more than 10% of a test surface, the evaluation was “NG”. The evaluations “AA”, “A”, and “B” were regarded as being acceptable.

Post-Coating Corrosion Resistance

[0086] The post-coating corrosion resistance was evaluated as follows.

[0087] After 7 g/m.sup.2 on the dry mass basis of the commercially available epoxy resin coating for can was applied to the surface of the test material of the Sn-based plated steel sheet produced and subjected to the humidity cabinet test according to the method described in the above [Coating film adhesiveness], the test material was baked at 200° C. for 10 minutes and placed at room temperature for 24 hours. Then, the obtained Sn-based plated steel sheet was cut into a predetermined size and immersed in commercially available tomato juice at 60° C. for 7 days, and then the presence or absence of occurrence of rust was visually evaluated.

[0088] When there was no rust at all, the evaluation was “AA”, when there was rust in an area ratio of 5% or less of the whole test surface, the evaluation was “A”, when there was rust in an area ratio of more than 5% and 10% or less of the whole test surface, the evaluation was “B”, and when there was rust in an area ratio of more than 10% of the whole test surface, the evaluation was “NG”. The evaluations “AA”, “A”, and “B” were regarded as being acceptable.

Example 1

[0089] Table 1 lists cooling water immersion conditions before the formation of the zirconium oxide on the Sn-based plating layer and manufacturing conditions when forming conditions of the zirconium oxide are varied. The Sn-based plating was produced by an electrolytic method from a known ferrostan bath, and a quantity of electricity during electrolysis was varied so that the Sn coating weight per side was in a range of 0.2 g/m.sup.2 to 30.0 g/m.sup.2. Table 2 lists various properties of the obtained Sn-based plated steel sheets and results of property evaluations. Table 2 lists metal Sn equivalent contents of the Sn-based plating layer listed in Table 1 again. In all test pieces, zirconium contained in the coating was confirmed by XPS to be the zirconium oxide as specified in the present invention.

TABLE-US-00001 TABLE 1 COOLING WATER CATHODE ELECTROLYTIC TREATMENT IMMERSION TREATMENT CATHODE ELECTROLYTIC Sn PLATING TREATMENT SOLUTION CONTENT HEATING COOLING WATER HEATING ZIRCONIUM SOLUTION MANUFAC- IN TERMS AND TEMPER- AND ION CONCEN- TEMPER- TURING OF METAL MELTING HARDNESS ATURE MELTING TRATION ATURE METHOD Sn (g/m.sup.2) TREATMENT (ppm) (° C.) TREATMENT (ppm) (° C.) A1 2.8 YES 103 35 2.0 1400 35 A2 2.9 YES 108 35 2.0 1400 35 A3 2.8 YES 113 35 2.0 1400 35 A4 2.7 YES 142 35 2.0 1400 35 A5 2.8 YES 145 35 2.0 1400 35 A6 3.0 YES 156 35 2.0 1400 35 A7 2.8 YES 161 35 2.0 1400 35 A8 2.9 YES 195 35 2.0 1400 35 A9 2.9 YES 195 35 2.0 1400 35 A10 2.8 YES 183 35 2.0 1400 35 A11 3.1 YES 212 35 2.0 1400 35 A12 3.1 YES 216 10 2.0 1400 35 A13 2.7 YES 219 50 2.0 1400 35 A14 2.8 YES 216 80 2.0 1400 35 A15 2.9 YES 220 35 0.5 1400 35 A16 2.9 YES 224 35 3.0 1400 35 A17 2.8 YES 219 35 5.0 1400 35 A18 3.1 YES 212 35 2.0 1000 35 A19 2.8 YES 221 35 2.0 2000 35 A20 2.7 YES 229 35 2.0 3000 35 A21 2.8 YES 233 35 2.0 4000 35 A22 2.7 YES 221 35 2.0 1400 5 A23 2.9 YES 226 35 2.0 1400 15 A24 2.8 YES 225 35 2.0 1400 40 A25 2.8 YES 220 35 2.0 1400 50 A26 2.9 YES 220 35 2.0 1400 35 A27 2.9 YES 216 35 2.0 1400 35 A28 2.8 YES 219 35 2.0 1400 35 A29 2.8 YES 216 35 2.0 1400 35 A30 2.8 YES 214 35 2.0 1400 35 A31 2.8 YES 213 35 2.0 1400 35 A32 2.9 YES 290 35 2.0 1400 35 A33 2.9 YES 294 35 2.0 1400 35 A34 2.8 NO 298 35 2.0 1400 35 A35 1.2 YES 201 35 2.0 1400 35 A36 14.8 YES 213 35 2.0 1400 35 A37 1.9 YES 203 35 2.0 1400 35 A38 2.1 YES 203 35 2.0 1400 35 A39 4.8 YES 202 35 2.0 1400 35 A40 5.2 YES 203 35 2.0 1400 35 A41 8.0 YES 201 35 2.0 1400 35 A42 10.2 YES 205 35 2.0 1400 35 A43 13.1 YES 203 35 2.0 1400 35 B1 2.9 YES 79 35 2.0 1400 35 B2 2.8 YES 91 35 2.0 1400 35 B3 2.7 YES 96 35 2.0 1400 35 B4 2.8 YES 304 35 2.0 1400 35 B5 2.8 YES 317 35 2.0 1400 35 B6 2.9 YES 337 35 2.0 1400 35 B7 0.8 YES 240 35 2.0 1400 35 B8 30.0 YES 246 35 2.0 1400 35 B9 15.2 YES 212 35 2.0 1400 35 B10 2.8 YES 242 5 2.0 1400 35 B11 2.7 YES 246 5 2.0 1400 35 B12 2.8 YES 246 5 2.0 1400 35 B13 2.8 YES 246 95 2.0 1400 35 B14 2.8 YES 242 35 2.0 1400 35 B15 2.8 YES 246 35 2.0 1400 35 B16 2.8 YES 242 35 2.0 1400 35 B17 0.8 YES 242 35 2.0 1400 35 CATHODE ELECTROLYTIC TREATMENT FIRST SECOND ELECTROLYSIS ELECTROLYSIS CONDITION CONDITION MANUFAC- CATHODE ELECTROLYTIC CURRENT TREATMENT CURRENT TREATMENT TURING TREATMENT SOLUTION DENSITY TIME DENSITY TIME METHOD pH (A/dm.sup.2) (sec) (A/dm.sup.2) (sec) REMARKS A1 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A2 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A3 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A4 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A5 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A6 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A7 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A8 3.7 2.0 0.8 0.6 0.8 INVENTIVE EXAMPLE A9 3.7 3.0 0.8 0.8 0.8 INVENTIVE EXAMPLE A10 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A11 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A12 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A13 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A14 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A15 3.7 2.0 0.4 0.5 0.8 INVENTIVE EXAMPLE A16 3.7 2.0 1.2 0.5 0.8 INVENTIVE EXAMPLE A17 3.7 2.0 2.0 0.5 0.8 INVENTIVE EXAMPLE A18 3.7 2.0 0.8 0.4 0.8 INVENTIVE EXAMPLE A19 3.7 3.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A20 3.7 5.0 0.8 0.6 0.8 INVENTIVE EXAMPLE A21 3.7 7.0 0.6 0.8 0.8 INVENTIVE EXAMPLE A22 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A23 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A24 3.7 3.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A25 3.7 5.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A26 3.5 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A27 4.3 6.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A28 3.7 2.0 0.8 0.3 0.8 INVENTIVE EXAMPLE A29 3.8 4.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A30 3.9 7.0 0.6 0.5 0.8 INVENTIVE EXAMPLE A31 3.7 10.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A32 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A33 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A34 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A35 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A36 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A37 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A38 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A39 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A40 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A41 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A42 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE A43 3.7 2.0 0.8 0.5 0.8 INVENTIVE EXAMPLE B1 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B2 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B3 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B4 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B5 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B6 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B7 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B8 3.7 2.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B9 3.7 2.0 0.8 0.5 0.8 COMPARATIVE EXAMPLE B10 3.7 0.5 0.8 0.8 0.8 COMPARATIVE EXAMPLE B11 3.7 11.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B12 3.7 12.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B13 3.7 13.0 0.8 0.8 0.8 COMPARATIVE EXAMPLE B14 3.7 2.0 0.8 — — COMPARATIVE EXAMPLE B15 3.7 10.0 0.8 — — COMPARATIVE EXAMPLE B16 3.7 3.0 0.8 12 0.8 COMPARATIVE EXAMPLE B17 3.7 2.0 0.8 0.5 0.8 COMPARATIVE EXAMPLE

TABLE-US-00002 TABLE 2 COATING LAYER ZIRCONIUM OXIDE Sn NUMBER OF PLATING DETECTED CONTENT CONTENT LOCATIONS OF IN TERMS IN TERMS CRYSTAL- AMORPHOUS PROPERTY EVALUATION MANUFAC- OF METAL OF METAL LINE LAYER STRUCTURE SURFACE COLOR TONE TURING Sn Zr LOWER UPPER IN UPPER RATIO INITIAL No. METHOD (g/m.sup.2) (mg/m.sup.2) LAYER LAYER LAYER (%) b* a1 A1 2.8 4.0 AMORPHOUS CRYSTAL- 7 30 2.7 LINE a2 A2 2.9 4.0 AMORPHOUS CRYSTAL- 6 40 2.8 LINE a3 A3 2.8 4.0 AMORPHOUS CRYSTAL- 6 40 2.8 LINE a4 A4 2.7 4.0 AMORPHOUS CRYSTAL- 6 40 2.9 LINE a5 A5 2.8 4.0 AMORPHOUS CRYSTAL- 5 50 2.8 LINE a6 A6 3.0 4.0 AMORPHOUS CRYSTAL- 2 80 2.7 LINE a7 A7 2.8 4.0 AMORPHOUS CRYSTAL- 1 90 2.8 LINE a8 A8 2.9 5.0 AMORPHOUS CRYSTAL- 1 90 2.6 LINE a9 A9 2.9 8.0 AMORPHOUS CRYSTAL- 4 60 3.0 LINE a10 A10 2.8 4.0 AMORPHOUS CRYSTAL- 1 90 2.7 LINE a11 A11 3.1 4.0 AMORPHOUS CRYSTAL- 1 90 2.9 LINE a12 A12 3.1 4.0 AMORPHOUS CRYSTAL- 1 90 2.8 LINE a13 A13 2.7 4.0 AMORPHOUS CRYSTAL- 1 90 2.8 LINE a14 A14 2.8 4.0 AMORPHOUS CRYSTAL- 1 90 2.6 LINE a15 A15 2.9 3.0 AMORPHOUS CRYSTAL- 1 90 2.9 LINE a16 A16 2.9 6.0 AMORPHOUS CRYSTAL- 1 90 2.9 LINE a17 A17 2.8 7.0 AMORPHOUS CRYSTAL- 1 90 2.8 LINE a18 A18 3.1 2.0 AMORPHOUS CRYSTAL- 3 70 2.4 LINE a19 A19 2.8 6.0 AMORPHOUS CRYSTAL- 1 90 2.6 LINE a20 A20 2.7 8.0 AMORPHOUS CRYSTAL- 1 90 2.9 LINE a21 A21 2.8 10.0 AMORPHOUS CRYSTAL- 4 60 3.1 LINE a22 A22 2.7 1.0 AMORPHOUS CRYSTAL- 5 50 2.2 LINE a23 A23 2.9 2.0 AMORPHOUS CRYSTAL- 1 90 2.3 LINE a24 A24 2.8 5.0 AMORPHOUS CRYSTAL- 1 90 2.5 LINE a25 A25 2.8 7.0 AMORPHOUS CRYSTAL- 1 90 2.7 LINE a26 A26 2.9 2.0 AMORPHOUS CRYSTAL- 1 90 2.2 LINE a27 A27 2.9 8.0 AMORPHOUS CRYSTAL- 1 90 2.9 LINE a28 A28 2.8 2.0 AMORPHOUS CRYSTAL- 1 90 2.3 LINE a29 A29 2.8 3.0 AMORPHOUS CRYSTAL- 3 70 2.7 LINE a30 A30 2.8 5.0 AMORPHOUS CRYSTAL- 3 70 2.7 LINE a31 A31 2.8 8.0 AMORPHOUS CRYSTAL- 3 70 2.5 LINE a32 A32 2.9 4.0 AMORPHOUS CRYSTAL- 6 40 2.4 LINE a33 A33 2.9 5.0 AMORPHOUS CRYSTAL- 7 30 2.5 LINE a34 A34 2.8 4.0 AMORPHOUS CRYSTAL- 7 30 2.5 LINE a35 A35 1.2 5.0 AMORPHOUS CRYSTAL- 5 50 1.7 LINE a36 A36 14.8 4.0 AMORPHOUS CRYSTAL- 5 50 4.5 LINE a37 A37 1.9 5.0 AMORPHOUS CRYSTAL- 5 50 1.9 LINE a38 A38 2.1 5.0 AMORPHOUS CRYSTAL- 5 50 1.9 LINE a39 A39 4.8 5.0 AMORPHOUS CRYSTAL- 5 50 2.8 LINE a40 A40 5.2 5.0 AMORPHOUS CRYSTAL- 5 50 2.8 LINE a41 A41 8.0 5.0 AMORPHOUS CRYSTAL- 5 50 3.2 LINE a42 A42 102 5.0 AMORPHOUS CRYSTAL- 5 50 3.5 LINE a43 A43 13.1 5.0 AMORPHOUS CRYSTAL- 5 50 4.2 LINE b1 B1 2.9 4.0 CRYSTAL- CRYSTAL- 10 0 3.1 LINE LINE b2 B2 2.8 4.0 CRYSTAL- CRYSTAL- 10 0 3.2 LINE LINE b3 B3 2.7 4.0 CRYSTAL- CRYSTAL- 10 0 3.3 LINE LINE b4 B4 2.8 4.0 CRYSTAL- CRYSTAL- 10 0 3.1 LINE LINE b5 B5 2.8 4.0 CRYSTAL- CRYSTAL- 10 0 3.3 LINE LINE b6 B6 2.9 4.0 CRYSTAL- CRYSTAL- 10 0 3.4 LINE LINE b7 B7 0.8 4.0 AMORPHOUS CRYSTAL- 3 70 2.3 LINE b8 B8 30.0 4.0 AMORPHOUS CRYSTAL- 3 70 4.3 LINE b9 B9 152 4.0 AMORPHOUS CRYSTAL- 5 50 4.5 LINE b10 B10 2.8 0.3 CRYSTAL- CRYSTAL- 10 0 2.2 LINE LINE b11 B11 2.7 11.0 CRYSTAL- CRYSTAL- 10 0 4.2 LINE LINE b12 B12 2.8 12.0 CRYSTAL- CRYSTAL- 10 0 4.5 LINE LINE b13 B13 2.8 14.0 CRYSTAL- CRYSTAL- 10 0 4.8 LINE LINE b14 B14 2.8 0.3 AMORPHOUS AMORPHOUS 0 100 2.2 b15 B15 2.8 14.0 AMORPHOUS AMORPHOUS 0 100 5.1 b16 B16 2.8 6.0 AMORPHOUS AMORPHOUS 0 100 3.4 b17 B17 0.8 5.0 AMORPHOUS CRYSTAL- 5 50 1.7 LINE PROPERTY EVALUATION SURFACE COLOR TONE Δb* b* BEFORE SULFUR- POST- AFTER AND AFTER COATING IZATION COATING HUMIDITY HUMIDITY FILM BLACKENING CORROSION CABINET CABINET ADHESIVE- RESIS- RESIS- No. TEST TEST NESS TANCE TANCE REMARKS a1 3.8 1.1 B A B B INVENTIVE EXAMPLE a2 4.1 1.3 B A B B INVENTIVE EXAMPLE a3 3.9 1.1 B A B B INVENTIVE EXAMPLE a4 3.9 1.0 B A B B INVENTIVE EXAMPLE a5 3.7 0.9 A A B B INVENTIVE EXAMPLE a6 3.6 0.9 A A A A INVENTIVE EXAMPLE a7 3.5 0.7 A A A A INVENTIVE EXAMPLE a8 3.1 0.5 A A A A INVENTIVE EXAMPLE a9 3.3 0.3 A B AA A INVENTIVE EXAMPLE a10 3.6 0.9 A A A A INVENTIVE EXAMPLE a11 3.1 0.2 A A A A INVENTIVE EXAMPLE a12 3.3 0.5 A A A A INVENTIVE EXAMPLE a13 3.5 0.7 A A A A INVENTIVE EXAMPLE a14 3.5 0.9 A A A A INVENTIVE EXAMPLE a15 3.5 0.6 A A A A INVENTIVE EXAMPLE a16 3.3 0.4 A A AA A INVENTIVE EXAMPLE a17 3.6 0.8 A A AA A INVENTIVE EXAMPLE a18 3.2 0.8 A A B B INVENTIVE EXAMPLE a19 3.4 0.8 A A AA A INVENTIVE EXAMPLE a20 3.1 0.2 A A AA A INVENTIVE EXAMPLE a21 3.4 0.3 A B AA A INVENTIVE EXAMPLE a22 3.1 0.9 A A B B INVENTIVE EXAMPLE a23 3.1 0.8 A A A A INVENTIVE EXAMPLE a24 3.4 0.9 A A A A INVENTIVE EXAMPLE a25 3.2 0.5 A A AA A INVENTIVE EXAMPLE a26 2.9 0.7 A A A A INVENTIVE EXAMPLE a27 3.5 0.6 A A AA A INVENTIVE EXAMPLE a28 2.9 0.6 A A A A INVENTIVE EXAMPLE a29 3.5 0.8 A A A A INVENTIVE EXAMPLE a30 3.3 0.6 A A A A INVENTIVE EXAMPLE a31 2.9 0.4 A A AA A INVENTIVE EXAMPLE a32 3.1 0.7 B A B B INVENTIVE EXAMPLE a33 3.1 0.6 B A B B INVENTIVE EXAMPLE a34 3.2 0.7 B A B B INVENTIVE EXAMPLE a35 1.8 0.1 A A B B INVENTIVE EXAMPLE a36 7.2 2.7 C B B A INVENTIVE EXAMPLE a37 2.2 0.3 A A B B INVENTIVE EXAMPLE a38 2.3 0.4 A A B A INVENTIVE EXAMPLE a39 3.6 0.8 A A B A INVENTIVE EXAMPLE a40 3.7 0.9 A A B AA INVENTIVE EXAMPLE a41 4.0 0.8 A A B AA INVENTIVE EXAMPLE a42 4.3 0.8 A A B AA INVENTIVE EXAMPLE a43 5.1 0.9 A A B AA INVENTIVE EXAMPLE b1 5.4 2.3 C B NG NG COMPARATIVE EXAMPLE b2 5.3 2.1 C B NG NG COMPARATIVE EXAMPLE b3 5.1 1.8 C B NG NG COMPARATIVE EXAMPLE b4 5.3 2.2 C B NG NG COMPARATIVE EXAMPLE b5 5.5 2.2 C B NG NG COMPARATIVE EXAMPLE b6 7.6 4.2 C B NG NG COMPARATIVE EXAMPLE b7 2.6 0.3 B A A NG COMPARATIVE EXAMPLE b8 7.4 3.1 C NG B A COMPARATIVE EXAMPLE b9 7.2 2.7 C B NG AA COMPARATIVE EXAMPLE b10 4.6 2.4 C B NG NG COMPARATIVE EXAMPLE b11 6.5 2.3 C NG NG NG COMPARATIVE EXAMPLE b12 6.7 2.2 C NG NG NG COMPARATIVE EXAMPLE b13 6.9 2.1 C NG NG NG COMPARATIVE EXAMPLE b14 4.6 2.4 B NG A A COMPARATIVE EXAMPLE b15 5.9 0.8 A NG AA A COMPARATIVE EXAMPLE b16 4.3 0.9 A NG AA A COMPARATIVE EXAMPLE b17 1.8 0.1 A A A NG COMPARATIVE EXAMPLE

[0090] It was found from Table 2 that al to a43, which were in the range of the present invention, were excellent in all performances. On the other hand, b1 to b17, which were comparative examples, were inferior in at least any of the yellowing resistance, the coating film adhesiveness, the sulphide stain resistance, or the post-coating corrosion resistance.

[0091] Preferred embodiments of the present invention have been described above in detail, but the present invention is not limited to the embodiments. It should be understood that various changes and modifications are readily apparent to those skilled in the art who has the common general knowledge in the technical field to which the present invention pertains, within the scope of the technical spirit as set forth in claims, and they should also be covered by the technical scope of the present invention.