JPH0232360B2 - CHAKUSHOKUAENMETSUKIKOHANNOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention generally relates to a method for producing a colored galvanized steel sheet for use in members requiring decoration in fields where galvanized steel sheets are used. (Prior Art) Surface-treated steel sheets are used in a wide range of fields because of their general-purpose quality and low cost, and it is certain that the demand for them will continue to increase due to their quality and effectiveness. Improvements in the quality of galvanized steel sheets have led to the creation of many new products in terms of appearance, rust prevention, workability, and paintability, as well as the high quality of the base material.
We have responded to the demands of the building materials field. In recent years, customer demands have led to the introduction of surface-treated steel sheets that aim to minimize total costs and simplify treatment processes while improving product quality. That is, conventionally, after processing a surface-treated steel sheet,
By introducing pre-coated steel sheets to products that have been pre-treated and painted, we can omit the pre-treatment and painting that were performed in the customer process, and produce high-quality products at low cost. This is one of them. Initially, high-grade pre-painted steel sheets with a thickness of 20 to 30μ were used as pre-painted steel sheets that could meet these demands, but in the pursuit of thorough cost reduction and from the viewpoint of weldability, there was a demand for colored surface-treated steel sheets. ing. In addition to corrosion resistance and workability, it is important for materials to have uniformity in appearance in order to meet these demands, and weldability and chemical resistance are also required as necessary. Black-ish colors are preferred. A known technique known for the color treatment of galvanized steel sheets is the method of JP-A-52-45544 (Private) of treating galvanized steel in a chromate solution containing silver ions, based on phosphoric acid and silver phosphate. There is a method disclosed in JP-A No. 58-177477 (Kyoto Chromate Industries) that involves treatment in a chromate solution. These methods eutectoid silver oxide on a chromate film to obtain a black appearance. Furthermore, as a method for blackening treatment by forming sulfides, a method disclosed in Japanese Patent Application Laid-open No. 52-65139 (foreign) has been disclosed. Furthermore, as a method for coloring a chromate film using a dye after forming it, the method disclosed in Japanese Patent Application Laid-open No. 54-145336 (Mitsui Kinzoku Mining) and Japanese Patent Publication No. 52-28730 (Mitsui Kinzoku Mining) has been disclosed. All of these methods involve a direct chemical reaction between a solution and galvanizing to obtain a colored surface. In addition, a method of obtaining a black surface by an anodic oxidation method has been disclosed. For example, Ni, Co,
The method of JP-A-151491, in which Mo and Zn alloy plated steel sheets are anodized in an aqueous ammonium sulfate solution;
Representative published techniques include the method disclosed in Japanese Patent Application Laid-Open No. 151490 (1982), which involves anodizing in an alloy plating bath of Ni, Co, Mo and Zn. (Problems to be Solved by the Invention) Conventional coloring methods are excellent methods, but unfortunately they do not necessarily match the manufacturing equipment owned by steel manufacturers. For example, shorter processing times are required for high-speed productivity. In addition, in the case of blackening treatment of zinc plating using conventional methods, the black film immediately after treatment is gel-like and has poor adhesion, which is a major hindrance to coil production and requires hardening treatment, which makes the process difficult. It's getting complicated. In any case, we have never experienced a method of uniformly coloring a wide coil product using a method other than painting. The present invention provides a method for obtaining uniform black galvanized steel sheets at high speed and in a short time under current process conditions. (Means for solving the problem) As mentioned above, one of the problems with coloring galvanized steel sheets is the formation of gel-like substances immediately after blackening treatment and poor adhesion due to corrosion of the underlying zinc. .
Various solutions can be considered to solve this problem, but basically it is effective to suppress the dissolution of the underlying zinc and form an unhydrated, compact film, such as a continuous film such as plating. That is, the present invention has succeeded in obtaining a colored film with good adhesion on the surface of a galvanized steel sheet in a short period of time in a state where the length is short enough to allow dissolution of the zinc plating. The present invention is comprised of the following components. That is, zinc ion 0.1-1 mol/, nickel ion 0.1-1 mol/, iron ion 0.01-0.2 mol/
Add 0.01 to 0.5 mol/vanadium ion, molybdenum ion, or chromium ion to the aqueous solution of
The problem was solved by a method for producing a colored galvanized steel sheet, which is characterized in that the galvanized steel sheet is electrolytically treated at 20 to 200 coulombs per 1 dm ² in an aqueous solution, and then coated with a protective film. The present invention will be described below. The electrolytic bath used in the present invention can be colored by cathodic electrolytic treatment in an aqueous solution containing metal ions as described above. The deposited colored film is composed of a composite film of zinc, an alloy mainly composed of nickel, and metal oxides. In the present invention, it is necessary to co-deposit a colored oxide, especially a black oxide, into a composite. Therefore, special conditions must be provided to the plating bath and electrolytic conditions for oxide precipitation at the cathode. In a zinc-only bath, it is difficult to eutectoid oxides and it is difficult to obtain the desired colored film in a short time. Due to the presence of nickel ions and iron ions, oxides eutectoid along with metal precipitation. In a Ni-only bath, zinc plating was used as the main component because of the generation of hydrogen and the large potential difference with the underlying zinc plating.
Composite plating of Zn-Ni-Oxides is the best.
The oxide of the composite must not be reduced to metal. Therefore, a compound that is a transition element and has a high valence is selected, and is precipitated as a low valence oxide in the reduction process. Does not reduce to metal in aqueous solution
With the exception of Ti ions, any of divalent, trivalent and tetravalent Ti ions can be applied. Composite plating has the disadvantage that a thick film cannot provide sufficient processing adhesion, so a thin film is required. The present invention will be explained below in terms of treatment bath, electrolytic conditions, and protective coating. One of the electrolytic baths used in the present invention is zinc ion 0.1
~1 mol/, Nickel ion 0.1-1 mol/,
Containing 0.01 to 0.2 mol of iron ions, preferably with a molar concentration ratio of nickel ions to zinc ions (Ni/Zn ratio) of 0.2 to 2.0, facilitates blackening.
Metal ions (described below as colored metal ions) 0.01 to 0.5 are added to the treatment bath containing these ions.
mol/added aqueous solution. The pH of the bath is the degree of coloring,
It varies depending on the electrolytic conditions, and a value of 1 to 4 is desirable in order to obtain a black appearance. The reasons for determining these conditions are as follows. If the concentration of zinc ions and nickel ions is less than 0.1 mol/mol, precipitation will be insufficient and a colored appearance will not be obtained. When the amount exceeds 1.0 mol/mol, zinc and nickel preferentially precipitate, making it difficult for oxides to co-deposit, making it impossible to obtain a sufficient colored appearance. When obtaining a black appearance, if the Ni/Zn ratio is less than 0.2, the nickel eutectoid rate is low, and the amount of oxide induced to eutectoid by nickel precipitation is low, resulting in a low blackness. If the Ni/Zn ratio exceeds 2.0, hydrogen gas is generated due to a decrease in hydrogen overvoltage, resulting in unevenness and insufficient coloring. Further, iron ions have the effect of promoting the precipitation of oxides, and are added in a range of 0.01 to 0.2 mol/. 0.01
If the amount is less than mol/mol, the effect is weak and coloring is difficult. 0.2
If the amount exceeds mol/mol, adverse effects of iron occur. That is, problems such as uneven appearance, pale color tone, and formation of precipitates in the bath occur. The colored metal ion (sometimes abbreviated as Me ⁿ⁺ ) is a polyvalent metal ion such as a vanadium ion, a molybdenum ion, or a chromium ion. Vanadium ions are 2-, 3-, 4-, and 5-valent ions; molybdenum ions are 2-, 3-, and 4-valent ions; and chromium ions are 3-, 6-valent ions. These metal ions are difficult to precipitate in a single bath;
Induced precipitation occurs due to the precipitation of zinc, nickel, and iron.
Therefore, the concentration of these metal ions is determined based on the degree of coloring and the mixing ratio of zinc, nickel and iron plating as a vehicle, particularly from the viewpoint of processing adhesion and adhesion immediately after cathodic electrolytic treatment. Concentration is 0.001~
It is 0.5 mol/. Preferably, the coloring metal ion concentration ratio (Me ⁿ⁺ /(Zn ²⁺ + Ni ²⁺ + Fe ²⁺ + Fe ³⁺ )) to the total concentration of vehicle metal ions is 0.025 to
Good appearance and quality can be easily obtained with 0.25. The lower limit of the concentration of each coloring metal ion is insufficient coloring due to insufficient eutectoid, and the upper limit is oxide that does not precipitate and tends to have a metallic glossy appearance, and even if a black appearance is obtained, powdering may occur. This is because powder-like flaking called . In terms of powdering, the (Me ⁿ⁺ / (Zn ²⁺ + Fe ²⁺ + Fe ²⁺ + Fe ³⁺ )) ratio is 0.025.
~0.25 is preferred. When the pH of the bath is low, the degree of blackness is low, and when the pH is high, the degree of blackness is high. If it is less than 1, it tends to peel off immediately after cathodic electrolytic treatment due to etching of the zinc surface, so the electrolytic conditions should be adjusted. 4 or more will produce a precipitate, but these may be caused by complexing agents such as citric acid, EDTA,
This can be solved by adding tartaric acid, etc. However, the vehicle metal is difficult to precipitate, and the pH is preferably 1 to 1.
It is preferable to do this at 4. Further, in order to lower the electrolytic voltage, a bath to which a conductive additive is added is also within the scope of the present invention. By adding a brightener to the treatment bath of the present invention, a smooth colored galvanized steel sheet with a high degree of blackness can be obtained. Examples of brighteners include water-soluble cationic and nonionic polymer compounds such as amines having secondary to tertiary amines in their side chains, polymers and their copolymers, polyacrylamide, dextrin, and the like. The amount added varies depending on the compound and ranges from 0.01 to 1.
g/. Polyacrylamide is effective in brightening at low concentrations. In the case of polyamine sulfone compounds, amine polymers are highly effective in brightening and blackening over a wide range of areas. In addition, starches and sugars such as dextrin have a greater glossing effect at higher concentrations. These additives smooth out the deposited composite plating and give it a transparent color tone. Moreover, it provides a film with uniform deposition and fewer pinholes on the unevenness of the plating base. Amine polymers are particularly effective in blackening treatment. The electrolysis conditions will be described. As described above, the present invention requires conditions for eutectoiding the vehicle metal and the oxide, and it is necessary to set the coulomb amount as the electrolytic conditions. . The present invention uses cathodic electrolysis in the range of 20 to 200 coulombs per dm ² . Outside this range, it is difficult to obtain blackish coloring. Current density is 5~
A value of 50 A/dm ² is preferable, but it varies depending on the electromechanical cell conditions. The bath temperature may be within the usual electrolysis condition range of 20 to 60°C. The protective film will be explained in detail below. By further coating the colored film formed by cathodic electrolytic treatment with a protective film, a more excellent appearance is provided, as well as corrosion resistance, workability, and scratch resistance. These films can be classified into three types: inorganic, organic, and organic-inorganic. Inorganic types include chromate film, phosphate film, silicate film, and zirconate film. These films are finished by applying an aqueous solution onto the colored surface, controlling the film thickness, and then drying or baking.
Alternatively, coating may be performed by electrolytic treatment in these aqueous solutions. Furthermore, layered coating, in which a chromate film is treated and then an organic film is applied, is the most excellent method for improving quality. In these cases, inorganic coatings are preferable as the lower layer coating. As organic systems, chelate compounds, tannic acid, phytic acid compounds, water-soluble polymers, or water-dispersible emulsions are applied together with a hardening agent onto a colored plated steel plate, the film thickness is controlled, and the finish is finished by drying or baking. Alternatively, it is coated by electrolytic treatment.
Organic/inorganic systems include water-soluble or water-dispersed organic polymer compounds and inorganic polymers (e.g. silica, alumina,
zirconia), etc. Alternatively, a method in which an aqueous solution or emulsion prepared by adding chromate, condensed phosphoric acid, zirconic acid, or a silane compound is applied onto a colored plated steel plate, the film thickness is controlled, and then dried and baked.
Alternatively, it is coated by electrolytic treatment. By coating these protective films on the black plating, the above-mentioned properties are added and a more practical pre-coated steel sheet can be obtained. Also, wax finishing etc. can be used from the viewpoint of improving appearance and workability. The film thickness is preferably 3μ or less for organic and organic-inorganic systems, and 1μ or less for inorganic systems. One of the coating methods is roll coating, or a conventional method of controlling the film thickness using a squeezing roll or an air knife after coating. The baking temperature is preferably 60 to 150℃. The second method is to apply the coating by electrolytic treatment, wash it with water or squeeze it with a roll, or squeeze it with an air knife if necessary, and then dry it. (Example) The present invention will be described in detail below with reference to Examples. Example 1 Zinc sulfate (ZnSo _{4.7H 2} O) 100g (0.34 mol),
100 g (0.35 mol) of nickel sulfate (NiSO ₄ .6H ₂ O) and 50 g (0.17 mol) of ferrous sulfate (FeSO ₄ .7H ₂ O) were dissolved in water. (Ni/Zn≒1). Furthermore, an electrogalvanized steel sheet (fabric weight 20 g) was prepared in a treatment bath (PH = _3.0 ) in which 10 g (0.06 mol, 0.08 mol) of vanadyl sulfate (VOSO ₄ 6H ₂ O) and ammonium metavanadate (NH ₄ VO 3 ) were separately added. /m ² ) was used as a cathode for electrolytic treatment. Bath temperature 50℃, current density 20A/dm ² ,
It was conducted at 50 coulombs/ ^dm2 . After electrolytic chromic acid treatment (total chromium: 30 mg/m ² ) as a protective film, 1μ of a composite bath of acrylic emulsion and silica was applied and baked with hot air at a plate temperature of 120°C for a short time. The quality of the colored plated steel sheet obtained is L.
The value (value representing brightness) is 12 to 13 with a black glossy appearance and a salt spray test (hereinafter abbreviated as S, S, T: JIS
No rust was observed for 120 hours using Z2371 continuous method).
Also, no peeling was observed even after press working to a depth of 30 mm. Furthermore, when an aqueous solution of sodium silicate was applied as a protective coat instead of acrylic emulsion and silica, the L value was 12 to 13, and no rust was observed at an SST of 72 hours. Example 2 Zinc sulfate 50g/(0.17 mol/), nickel sulfate 70g/(0.25 mol/), ferrous sulfate 20
g/(0.07 mol/), ammonium sulfate 50
ammonium molybdate in an aqueous solution of
(0.02 mol/), 10(0.04 mol/)
15A/dm ² , coulomb amount 100 coulombs/dm ² ). Next, an aqueous solution of colloidal silica and chromic acid was applied, dried with hot air, and chromate treated (total chromium: 25 mg/m ² ), and then an ammonia aqueous solution of polyacrylic acid and zirconic acid, pH=6, was applied and the plate temperature was lowered.
Baked at 120℃. A black appearance with an L value of 12 is obtained,
No rust occurred after 120 hours of SST, and no peeling was observed when bent at 180°C with a diameter of 3 mm. Example 3 In place of ammonium molybdate in Example 2, colored metal ions shown in Table 1 were added, and the same treatments and evaluations were carried out.

[Table] Example 4 A galvanized steel sheet was subjected to cathodic treatment under the same conditions in a treatment bath in which 10 g/polyamine sulfone polymer was added to the treatment bath of Example 1. A protective film of 0.5μ of acrylic emulsion, ammonium chromate, and silica was applied to the treated steel sheet, and the plate temperature
Baked at 100℃. The L value was 12 to 11, and the corrosion resistance showed no white rust after 120 hours of salt water spraying. Example 5 Zinc sulfate 100g/(0.34 mol/) Nickel sulfate 100g/(0.35 mol/) Ferrous sulfate 50
g/(0.17 mol/), 20 g/(0.1 mol/) of sodium molybdate, and 100 ppm of polyacrylamide.
After cathodic electrolytic treatment at 150 coulombs/ ^{dm 2} ,
A commercially available coated chromate was applied at 25mg/ ^m2 of total chromium and dried with hot air, then 1μ of a solution consisting of an emulsion of polyethyleneimine and silica gel and a silane coupling agent was applied and baked at a board temperature of 120°C. It had a black appearance with an L value of 13, and its color fastness did not rust for 48 hours at a 90° bend. Also, instead of applying chromate, use commercially available phosphate treatment for 1/4 hour (30 seconds) of the normal treatment (2 minutes spray).
After that, a similar coating evaluation was performed. The L value is
14. Corrosion resistance was only 2% rusted at the 90° bend. (Effects of the Invention) The present invention is a steel plate that is a decorative galvanized steel plate that is relatively inexpensive and has anti-corrosion properties.It has an appearance similar to a conventional coated steel plate, and has inorganic characteristics such as hardness and scratch resistance. Quality effects such as The biggest advantage is that mass production at low cost is possible. In order to convert conventional post-coating materials into pre-coating materials, it is necessary to have characteristics that incorporate various operations in the customer process, and there are limits to using only aerobic coatings, so the present invention is one of the advancements in this field. be.

Claims (1)

[Claims] 1 Zinc ion 0.1-1 mol/, Nickel ion 0.1-1 mol/, Iron ion 0.01-0.2 mol/
Add one or more of vanadium ions, molybdenum ions, and chromium ions to an aqueous solution of 0.01~
1. A method for producing a colored galvanized steel sheet, which comprises subjecting the galvanized steel sheet to electrolytic treatment at 20 to 200 coulomb per 1 dm ² in an aqueous solution containing 0.5 mol/mole as a cathode, followed by coating with a protective film.