JPS62103394A - Colored chromate alloy plated steel sheet - Google Patents

Abstract

PURPOSE:To produce a steel sheet having beautiful color tones and excellent corrosion resistance and workability by subjecting the steel sheet having a plating layer of a Zn-Ni alloy to a chromate treatment contg. water-soluble hexad Cr and halogen ions and further forming a guard coat layer thereon. CONSTITUTION:The steel sheet plated with the Zn-Ni alloy contg. 8-20% Ni is subjected to the chromate treatment with a chromate bath essentially consisting of the water-soluble hexad Cr such as chromic anhydride, dichromate or chromate and halogen ions such as chlorine ions, fluorine ions or silicofluoride ions. The guard coat layer consisting of an org. polymer, inorg. polymer, chelate compd. and the composite film thereof as well as oil and fats and oils, etc. is coated thereon by spraying, etc. The Zn-Ni alloy plated steel sheet having the beautiful color tones of a black or brown system and having the excellent corrosion resistance, workability, flawing resistance and chemical resistance is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a black galvanized steel sheet used for members requiring decoration, corrosion resistance, and workability in fields where galvanized steel sheets are generally used.

[Conventional technology]

Low-cost, high-performance quality has always been required for rust-proof steel sheets for automobiles, home appliances, furniture, and steel sheets used in the building materials field. In response to these demands, steel manufacturers have developed new technologies and products to meet the demands of customers.

Recently, by introducing pre-coated steel sheets, pre-treatment and painting that were performed in the customer process can be omitted for products that have conventionally been pre-treated and painted after processing surface-treated steel sheets, making it possible to achieve lower costs and higher costs. There is a growing movement toward using prepainted steel sheets to obtain high-quality products.

Initially, high-grade pre-painted steel sheets with a thickness of 20 to 30 μm were used as pre-coated steel sheets that could meet these demands, but from the viewpoint of thorough cost reduction and weldability, colored surface-treated steel sheets are desired. .

The qualities that materials should have to meet these demands are:
In addition to corrosion resistance and workability, uniformity of appearance is important, and weldability and chemical resistance are required as necessary. Black-ish colors are preferred.

A known technique known for the coloring treatment of galvanized steel sheets is the method of JP-A-52-45544 of treating galvanizing in a chromate solution containing silver ions, based on phosphoric acid and silver phosphate. There is a method disclosed in JP-A-58-177477 which 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 forming sulfides and performing blackening treatment, a method disclosed in Japanese Patent Application Laid-Open No. 52-65139 is known. Furthermore, as a method of coloring the chromate film using a dye after forming it, the methods disclosed in Japanese Patent Application Laid-open No. 145336/1982 and Japanese Patent Publication No. 28730/1982 are known. 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 is known. For example, Ni.

JP-A-58-151491 discloses a method of anodizing a Go, Mo, and Zn alloy plated steel sheet in an aqueous ammonium sulfate solution, and JP-A-58-151490 discloses an anodizing process in a Ni, Go, Mo, and Zn alloy plating bath. The method disclosed in the above publication is a typical technique.

[Problem that the invention seeks to solve]

Conventional coloring methods are excellent, but unfortunately they do not always match the manufacturing equipment that steel manufacturers have. For example, in terms of high-speed productivity, it is necessary to complete uniform coloring in a shorter time. In addition, it is an unprecedented chemical conversion treatment technology that can stably obtain large quantities of wide rjj coil products with a uniformly colored appearance.

The present invention provides galvanized products with uniform color tone at high speed and in a short time.

The colored chromate alloy plated steel sheet of the present invention has a beautiful black or brown color tone, and also has excellent corrosion resistance and workability due to the action of chromate. In addition, the chromate alloy plated steel sheet of the present invention coated with a guard coat is
The appearance, corrosion resistance, and workability are further improved, as well as scratch resistance and
Quality such as chemical resistance is ensured, and it has the performance as a new pre-painted steel sheet to replace the conventionally used painted steel sheet.

[Means and effects for solving the problem] The colored chromate alloy plated steel sheet referred to in the present invention includes the following two types.

(1) After plating the top layer with an alloy containing zinc and nickel as its main components, a colored chromate layer is formed by chemically treating it with a chromate bath containing water-soluble hexavalent chromium and halogen ions as its main components. Colored chromate alloy plated steel sheet.

(2) After plating the top layer with an alloy mainly composed of zinc and nickel, a colored chromate is formed by chemical treatment with a chromate bath containing water-soluble hexavalent chromium and halogen ions as the main components. Colored chromate alloy plated steel sheet with a guard coat layer formed by coating.

The present invention will be described in detail below.

First, the colored chromate alloy plated steel sheet of the present invention will be described. The present invention is a colored chromate alloy plated steel sheet having a colored chromate film obtained by chemically treating a zinc-nickel alloy plating containing Ni (hereinafter referred to as Ni-Zn alloy plated steel sheet) in a chromate treatment bath as described below in the uppermost layer. be. The colored chromate film is a composite film composed of oxides or hydroxides of nickel, chromium, and zinc.

Although a very small amount of halide is contained, most of it is diffused into the chromate bath or removed by washing with water as a soluble salt. The Ni-Zn alloy plated steel sheet of the uppermost layer is likely to be colored if it contains 3% or more of Ni, but it is preferably 8 to 20%. For example, a Ni-Zn alloy plated steel sheet containing 12% Ni is
In order to obtain a black appearance with the chemical treatment with the chromate bath of the present invention, 3 g/rn' of plating is eluted as a weight loss.

If the N1 content is low, it is necessary to increase the amount of plating elution in order to obtain a black appearance. Furthermore, if the N1 content is too high, a passive film is likely to be formed, and the processing time is likely to be long, resulting in non-uniformity. In addition to nickel and zinc, Sn, Cu, Co, Fe,
A plated steel plate containing Cr as a third element is also a colored chromate alloy plated steel plate of the present invention. Ni-Zn alloy plated steel sheets tend to form cracks due to corrosion if they contain 10% or more of Ni, and general acid dissolution treatment has the problem of deteriorating corrosion resistance and workability.

Since the present invention forms an amorphous chromate film while dissolving the Ni-Zn alloy, cracks are protected by the chromate film. Therefore, even after coloring, corrosion resistance and processability do not deteriorate, and rather, a high quality product can be obtained due to the composite oxide chromate film formed. For example, in addition to being corrosion resistant and processable, it is also resistant to fingerprints, has a uniform color tone, and has a semi-glossy appearance. The color has blue, brown, brown and black tones by controlling the reaction amount of chemical treatment.

The colored chromate alloy plated steel sheet of the present invention includes a steel sheet in which a colored chromate film is coated with a guard coat.

The purpose of the guard coat is to improve quality. For example, the appearance will be more uniform and the degree of coloration will be stronger. Depending on the type and thickness of the guard coat, a steel plate with an appearance ranging from semi-gloss to gloss can be obtained. Also, resistance to scratches is improved. Particularly effective against press, handling, and contact scratches.

The effect of improving corrosion resistance is particularly large. The lower layer of the guard coat has a chromate layer and an alloy plating layer, and in examples where an organic film is used as the guard coat, the combined effect of the coating and the lower layer significantly improves corrosion resistance.

Regarding processability, the type of guard coat has a great effect on improving it.

The guard coat of the present invention is composed of an organic polymer, an inorganic polymer, a chelate compound, a composite film of these, oil, and fats and oils. The organic polymer requires a film made by coating a water-soluble or water-dispersible solvent-soluble organic polymer compound with a curing agent and hardening it by baking, etc., a coating film cured by ultraviolet light, or an organic polymer composited with an inorganic-organic compound. This is a film that is coated with a hardening agent and hardened by baking. Compounds to be combined include:
Chromium compounds, oxides such as silica, titania, alumina, and zirconia, inorganic compounds such as mica, talc, phosphates, and borates, fatty acid soaps, carbon, fatty acid esters, organic compounds of plastic particles, silane coupling agents, Organometallic compounds such as titanium coupling agents.

Examples of inorganic polymers include silicate compounds and sols of sodium silicate and lithium silicate, condensed phosphoric acid polymers, biphosphates, and zirconic acid polymers.

Chelate compounds include phytic acid and tannic acids. Known oils and fats may be used.

The method for manufacturing a colored chromate alloy plated steel sheet according to the present invention will be described below.

As described above, the present invention preferably uses N containing 3% or more of Ni.
After plating with an alloy mainly composed of 1 and zinc in a normal treatment bath, a chemical treatment is carried out by contacting with the following chromate bath. The alloy plating may contain the above-mentioned Ni as the uppermost layer, and may be single plating or multiple plating.

In the present invention, the chromate bath contains a water-soluble hexavalent chromium compound such as chromic anhydride, dichromate, or chromate as a first component, and halogen ions such as chloride ions,
The second component is a fluorine ion or a silicofluoride ion. In addition to these, metal ions, molybdic acid, boric acid, permanganic acid, chlorate, and peroxide may be added as necessary. Phosphoric acid, nitric acid, and phosphate ions are not preferred because they have a low degree of coloration and tend to become non-uniform.

The concentration of water-soluble hexavalent chromium varies depending on the degree of coloring, but in the case of black, it is 20 g/Q (Cr
O, 40 g/Q or more) or more is preferable. C
The upper limit of r+1' is Cr+', although there is no restriction regarding coloring.
As 75 g/Q (CrO3150g/
Q) The above methods have poor workability and tend to result in insufficient water washing.

As for halogen ions, chlorine ions are suitable for black appearance, and fluorine ions are suitable for brown appearance.

The concentration is 10-20 mQ with 35% HCQ for brown color.
/Q In the case of black, 20 m Q / Q or more is desirable at 35% HCQ. In the case of fluorine-based ions, the dissolving power of alloy plating is stronger than that of chlorine ions.< Compared to HCQ, it is easier to obtain better quality by aiming for a lower concentration. The pH of the chromate bath is not particularly specified, but a low pH tends to give a colored appearance in a short period of time.

The chemical treatment of the present invention will be described. Chemical treatments include methods that have the following mechanism of action.

1) Dissolve the alloy plating.

2) A portion of the dissolved metal ions is diffused into the bath, and a portion is oxidized by the action of chromic acid to form a composite film of metal oxide and chromate on the surface of the alloy plating.

3) Water-soluble compounds are removed by post-washing.

Specific chemical treatment methods include immersion, which brings the alloy-plated steel sheet into contact with the treatment bath, spraying for acceleration and uniformity, electrolysis using the alloy-plated steel sheet as an anode, or a combination of these methods. By adopting one of these, it is possible to deal with the diverse line configurations of steel manufacturers. In any case, in order to uniformly blacken a wide plated steel plate, it is necessary to apply chemical treatment uniformly, and it is necessary to adopt an optimal treatment method that matches the characteristics of the line.

Figure 1 shows chromic anhydride as a water-soluble hexavalent chromium compound,
Using a chromate bath containing chlorine ions (hydrochloric acid) as halogen ions, 12% Ni with a basis weight of 20 g/-
-Zn alloy plated steel plate as anode, current density 20
A/dm, current flow amount LOOC/dPo The relationship between the bath composition and blackness of a colored chromate alloy plated steel sheet that was washed with water after anodization and dried after chemical treatment is shown. As for the symbols in the figure, ◎ means black with an L value of 15 or less, ○ means black brown with 16 to 20, brown and blue appearance with Δ of 21 to 25, and X means gray appearance with an L value of 30 or more. Coloration is related to Cr concentration, HCQ concentration, and HCQ/Cr+ concentration ratio. Preferred areas are shown in Table 1.

The upper limit of each concentration is unclear, but in the case of Cr", it is practically advantageous to keep it below 75 g/Q in terms of workability and water washing. Also, the upper limit of HCl2 is R1.1 shown as 35%HCQ/Cr+6 ratio in Figure 1.
Although determined by R2 and R1, the higher the concentration, the greater the amount of plating dissolved, and 100 g/Q is practically desirable.

As can be seen from Figure 1 and Table 1, water-soluble hexavalent chromium and H
It can be seen that a colored appearance can be easily obtained by controlling the concentration of CQ. The results obtained by immersion treatment for 10 seconds using the same chromate bath were almost the same as those shown in FIG. The relationship between the bath composition and blackness varies depending on the alloy plating composition and the amount of chemical treatment, and is selected depending on the desired color tone and alloy plating composition. Also, when zinc ions increase in the bath, the color becomes brownish, but this can be adjusted by adding Cr+6 or HCQ.

A method for applying a guard coat on the colored chromate alloy film thus obtained will be described below.

Coating methods for Guard Coat include well-known roll coating, roll squeezing, spraying, air knife squeezing,
After coating by dipping or electrolytic treatment, heating (hot air, infrared rays, combustion furnace, electric heat) or ultraviolet curing can be used.

〔Example〕

Examples will be described below.

Explanation of symbols and numerical values in the examples Bath composition is Cry, amount is g/Q, I (C11 etc. is mQ/Q
is the unit of For chemical treatment, anodic treatment is performed at a current density of 20 A/drn'' and a current flow rate of 1 unless otherwise specified.
00C:/dm. Dipping is for 10 seconds, and spraying is for 3 seconds.

The L value is the brightness, and the gloss is the gloss value when a black glass plate is set to 93, and both were based on the method determined by JIS.

Adhesion was evaluated by peeling with 2T folding cellophane tape: O: no peeling, X: peeling.

Corrosion resistance is 5% white rust using JIS standard salt spray test.
Evaluated by time until occurrence, 5: 168 hours or more,
4: 120-168hrs, 3: 72-120hrs
s, 2: defined as 24-48 hrs, 1: defined as 10-24 hrs.

The index is those that remain (×) and those that do not increase (○).

Example 1 After performing 12±1% Ni-Zn alloy plating from a sulfuric acid bath, the chemical treatment shown in Table 2 was performed in the chromate bath shown in Table 1, followed by washing with water and drying to form colored chromate alloy plating. A steel plate was created. For comparison, Cry3 alone,
Cry, -H, PO4゜Cry, -HN○,, CrO2
-H,SO2 baths were also tested.

Samples No. 1 to 14 are Cr○, -HCQ bath of the present invention, N
o, 15-18 are comparative examples, and 19~ are examples of F- ions.

In the present invention, a white to brown to black chromate alloy plated steel sheet was obtained depending on the Cry:1-HCQ concentration. The quality of the white one was poor, but the brown and black ones had good quality (corrosion resistance, fingerprints).

Example 2 Ni-based alloy zinc plating containing 20 g/n (12±1% Ni and 0.2% Co) was washed with water from a sulfuric acid bath, and then 100 g/Q of CrO3, 35% 1-ICQ was applied.
The specimens were immersed in a chromate bath of 30 mQ/Q for 10 seconds, further washed with water, and coated with the guard coat shown in Table 3 using a roll coater to produce black chromate alloy plated steel sheets with guard tools 1 to 1.

The steel sheet of the present invention coated with the guard coat had a strong black semi-gloss appearance and exhibited very excellent corrosion resistance. Furthermore, as seen from sample No. 22.23, the gloss value can be changed by changing the thickness of the guard coat.

〔Effect of the invention〕

The colored chromate steel sheet according to the present invention has excellent appearance, workability, and corrosion resistance, and is a new steel sheet with strong resistance to scratches, and can be used in the field of conventional painted steel sheets, contributing to higher quality products and lower costs. .

In addition, the G2 structure allows for high-speed and short-time processing, so processing can be performed within a conventional electroplating line, resulting in a low loss of 1-.
can be realized.

In particular, the present invention provides coloring and chromate coating in a short time and
Since it can be achieved in passes, it is more effective than other coloring processes in terms of simplifying the processing process and ensuring quality.

[Brief explanation of drawings]

Figure 1 shows an example of the present invention showing the relationship between the blackness obtained when Ni-Zn alloy plating containing 12% N] was anodized in a chromate bath of Cr○, -HCQ and the bath composition. This is what is shown. The black area is within the dotted line area. Patent applicant: Nippon Steel Corporation / Yome representative Patent attorney: Yasushi Furushima 1:) Toy

Claims (2)

[Claims] (1) A colored chromate alloy plated steel plate having a colored layer formed by chemically treating a plated steel plate containing an alloy of zinc and nickel with a chromate bath containing water-soluble hexavalent chromium and halogen ions as main components. (2) Colored chromate alloy plating that has a coated steel sheet containing an alloy of zinc and nickel, which has a layer that is colored by chemical treatment in a chromate bath containing water-soluble hexavalent chromium and halogen ions as main components, and a guard coat layer. steel plate.