JPS6240387A - Pretreatment of copper electroplated steel sheet having superior sulfurizability - Google Patents

Abstract

PURPOSE:To introduce copper electroplated steel sheet to a sulfurizing stage in a cleaned surface state by subjecting the steel sheet to acid treatment with an aqueous soln. of HCl or H2SO4 as a treating soln. and one or more kinds of other specified treatments. CONSTITUTION:Before the copper surface of a copper electroplated steel sheet is sulfurized, the steel sheet is subjected to acid treatment with an aqueous soln. of HCl or H2SO4 having 0.5-10% concn. and one or more kinds of treatments selected among solvent treatment (A) with an aqueous soln. of an org. solvent having 1-10% concn., alkali treatment (B) with an aqueous soln. of sodium hydroxide or ammonia having 0.5-5% concn. and buffing (C) with buff of #150 or above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pretreatment method for improving the quality of sulfurization treatment of copper-plated steel sheets.

[Conventional technology]

Electrolytic copper-plated steel sheets, in which a copper plating layer is formed by electroplating on the surface of steel sheets such as stainless steel sheets, are subjected to sulfurization treatment through a slitting process to cut them into a predetermined width dimension, a skin pass process to correct the shape of the steel sheet, etc. attached to. Steel plates colored in a predetermined color through sulfurization can be used as building materials, decorations,
It is widely used as a material for various daily necessities.

The copper-plated surface of a copper-plated steel sheet is susceptible to discoloration and corrosion due to contact with the atmosphere after plating and before being introduced into the sulfiding process. When discoloration and corrosion occur, product quality deteriorates due to uneven sulfurization, and yield also decreases.

In order to prevent this uneven sulfurization, direct plating
□ Treat the steel plate with a discoloration inhibitor (e.g. chromic acid,
Alternatively, a solution containing a metal compound of benzotriazole and fatty acid amine) is used to form a discoloration-proof epithelial film on the plating surface, thereby blocking contact with the atmosphere and preventing discoloration and corrosion. In addition, in the slitting and skin pass processes that are performed before the sulfurization process, measures are taken to protect the anti-discoloration film by applying a putting material to prevent it from being damaged or peeled off. ing.

[Problem to be solved]

Despite forming an anti-discoloration film on the plating surface of copper-plated steel sheets as mentioned above to protect the plating surface,
When sulfurization treatment is performed, treatment unevenness often occurs. It is thought that the processing unevenness is mainly caused by the following four factors in the slitting and skin pass process of the steel plate. (1) When the anti-discoloration film rubs against the padding material applied as a protective measure, partial thinning of the film, deterioration of film properties, striation pressure, and peeling occur in the film; (2) ) The occurrence of discoloration, oxides, and corrosion products on the exposed copper plating surface in the damaged area; (3) Ununiform distortion occurs in the steel plate due to slits and skin passes, and this distortion causes discoloration, oxidation, corrosion, etc. (4) Additionally, oil and other dirt/foreign substances may adhere to the surface of the steel plate during the skin pass process, etc.

Therefore, in order to prevent uneven sulfurization, it is necessary to eliminate the non-uniformities in the surface properties of the steel sheet caused by the above-mentioned factors. What is important in this case is that the copper plating layer itself must not be damaged or its quality deteriorated. In addition, copper plating is often bright plating,
It is also necessary not to impair its luster.

From this point of view, the present invention eliminates the non-uniformity of the surface texture that causes uneven sulfurization without impairing the quality of the copper plating layer, and introduces the copper plating layer into the sulfurization process with a clean surface condition. This aims to improve the quality of sulfiding treatment.

[Means for solving problems]

The pretreatment method for electrolytic copper-plated steel sheets according to the present invention includes
．． Acid treatment with a 5-10% hydrochloric acid aqueous solution or sulfuric acid aqueous solution; (a) Solvent treatment with an aqueous solution containing an organic solvent with a concentration of 1-10%; (b) Hydroxylation with a concentration of 0.5-5%. Alkaline treatment with sodium or ammonia aqueous solution, (c') #1
It is characterized by performing one or more types of processing selected from buffing processing in which polishing is performed using 50 or more buffs. Note that the concentration (%) of each of the above-mentioned treatment liquids is % by weight.

[Effect]

In the pretreatment method of the present invention, the acid treatment using an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution as a treatment solution eliminates the discoloration film and oxides (Cu O% Cu z O) on the surface of the copper plating layer without causing erosion loss. , corrosion products (basic copper carbonate, etc.) are dissolved and removed.

Further, the anti-discoloration film is also sufficiently removed. The concentration of this acid aqueous solution is preferably 0.5 to 10%. The reason why the lower limit is set at 0.5% is that if it is lower than that, the dissolution removal power will be weakened and the treatment will take a long time.On the other hand, the upper limit is set at 10% because if it exceeds it, the copper plating layer will be damaged. This is because it dissolves.

FIG. 1 shows the relationship between the time required to clean the plating surface and the acid concentration of the treatment solution in acid treatment.

The test material is an electrolytic copper-plated steel sheet in which discolored areas (brown or bluing) account for 60% of the area.The horizontal axis of the figure is the HCl or HasO concentration of the treatment solution, and the vertical axis is the test material. It represents the time (seconds) required for the discolored pattern on the surface to completely disappear after it is thoroughly washed with a treatment solution. It can be seen that there is a clear correlation between acid concentration and treatment time, and that cleaning can be achieved within a relatively short time at a concentration of 0.5% or more.

In addition, when the copper plating layer is a bright plating, an aqueous hydrochloric acid solution is preferably used as the treatment liquid in order not to impair the gloss. A sulfuric acid aqueous solution may be used instead of a hydrochloric acid aqueous solution, but in that case, it is preferable to adjust the concentration to a low concentration of 0.5 to 3%.

In solvent treatment using an aqueous solution containing an organic solvent, oils and other dirt and foreign matter are dissolved and removed. Furthermore, if the anti-discoloration film is relatively thin, that film can also be sufficiently removed. Preferred examples of the solvent include methanol, ethanol, acetone, and the like. Two or more solvents may be used in combination. The solvent concentration of this treatment solution is 1 to 10%
shall be.

When two or more types of solvents are used together, the total concentration may be within the above range. The reason why the solvent concentration is set to 1% or more is because if it is lower than that, the dissolution and removal power will be weak and the treatment will take a long time. On the other hand, the reason why the upper limit is set at 10% is that even if it is added in excess of this amount, the film removal effect will hardly change.

When performing the above acid treatment and solvent treatment, these treatment solutions can be combined and carried out in one step using an aqueous solution containing the acid and solvent at the predetermined concentrations as the treatment solution. The relationship between the concentration of the treatment liquid and the time required for surface cleaning in this case is the same as that shown in FIG. 1 above.

In alkaline treatment using an aqueous solution containing sodium hydroxide or the like as a treatment liquid, oils, other dirt, and foreign matter are removed. The concentration of sodium hydroxide in the treatment solution is 0.5~
5%. The reason for setting the lower limit at 0.5% is that if it is lower than that, the ability to dissolve and remove oils etc. will be weak and the treatment will take a long time.On the other hand, the upper limit is set at 5% because the concentration is higher than that. Even so, the effect of removing oils etc. does not increase any further. As the treatment liquid, an aqueous solution containing ammonia at the above concentration can also be used instead of sodium hydroxide. In this case, a small amount of hydrogen peroxide (H20□) (for example, 0
．． It is desirable to add 5 to 2%).

When buffing is performed, oxides, corrosives, residual smut from oil, etc. on the plating surface are removed without losing the luster of the plating. In this case, the buff roughness is required to be #150 or higher. The reason why the thickness is #150 or more is because if it is rougher than that, problems such as scratches on the plating surface and grinding of the copper plating layer will occur.

This is because.

Among the above treatments, solvent treatment, alkali treatment and buffing treatment may be selected depending on the surface properties of the plating layer.
One or more are selected and carried out in combination with the acid treatment. Each of these treatments can be performed continuously by providing tanks containing the respective treatment liquids and sequentially passing the copper-plated steel sheets through the tanks. Although there is no essential restriction on the order in which each treatment is performed, the order of alkaline treatment, acid treatment, and buffing treatment is usually performed. Further, as described above, when performing solvent treatment, by using a treatment liquid containing an acid and a solvent, the acid treatment and the solvent treatment can be completed in one step.

The copper-plated steel sheet that has been pretreated according to the present invention is washed with water or hot water by spraying, etc., then drained and dried using a ringer roll, and subjected to sulfurization treatment. Since the plating surface is sufficiently cleaned and activated uniformly over the entire surface, no uneven treatment occurs, and a uniform and beautiful colored surface is formed over the entire surface of the steel plate.

Furthermore, since the pretreatment can impart or increase gloss to the plating surface, the finish of the sulfiding treatment is improved accordingly. The sulfurized copper-plated steel sheet is then finished into products through post-processes such as hairline processing.

〔Example〕

After passing the electrolytic copper-plated steel sheet that has been treated with an anti-discoloration film through a slitting and skin bath process, pre-treatment is carried out.
Then, sulfurization treatment was performed.

(1) Copper-plated steel sheet base, stainless steel sheet (thickness 0.3), plating thickness 21
0μm (2) Anti-discoloration film treatment Gospel #30 (manufactured by Gosbel Kako ■) as an anti-discoloration agent
By spraying an aqueous solution (concentration 0.7%) and drying with warm air, a discoloration prevention film (7゜0g/l") is created.
form.

(3) Slitting and Skin Bath of Steel Strip After slitting a steel strip with a width of 914 mm into three strips to a width of 250 mm, 0.8 to 1.0% of a dry skin bath is added for the purpose of surface conditioning.

(4) See Pretreatment Table 1. When acid treatment and solvent treatment were performed, an aqueous solution containing an acid and a solvent was used as the treatment liquid, and the acid treatment and solvent treatment were performed simultaneously. After the pretreatment, the sample was washed with water and hot water, and then drained using a ringer roll and dried.

(5) Sulfurization treatment bath composition: K, s 1.5%, NH, Cl 1.0% Bath temperature: room temperature A copper-plated steel sheet was immersed in the above bath (immersion time 4
5 seconds), a CuS film is formed on the plating surface and colored black.

Table 1 shows the plating surface properties under the above conditions, after pretreatment, and after sulfurization. "A treatment" in the pre-treatment conditions column
is acid treatment, "B treatment" is acid/solvent treatment that simultaneously performs acid treatment and solvent treatment using a treatment solution containing acid and solvent, "C treatment" is solvent treatment, and "D treatment" is Alkali treatment and "E treatment" each mean buffing treatment.

In addition, the meanings of the symbols in the same table are as follows.

"Gloss" item in the "Plating surface quality after pre-treatment" column O: Glossy ×: No gloss Other items in the "Plating surface quality after pre-treatment" column ○: Sufficient removal over the entire surface △ Ni Remaining ×: Remaining “Presence or absence of treatment unevenness after sulfiding treatment” column ○: No treatment unevenness 62 Partially slight treatment unevenness ×: Significant treatment unevenness As shown in Table 1, acid treatment according to the present invention By pre-treating in combination with one or more treatments selected from solvent treatment, alkali treatment, and buffing treatment, the plating surface becomes glossier and is sufficiently cleaned and activated.
A good product with no unevenness can be obtained during sulfurization. On the other hand, in a comparative example that lacks the requirements of the present invention,
The plating surface was insufficiently cleaned and activated, and uneven sulfurization treatment occurred, both of which were inferior to the examples of the present invention.

〔Effect of the invention〕

According to the pretreatment method of the present invention, non-uniformity in the surface properties of the copper-plated steel sheet before sulfurization treatment, especially non-uniformity in the thickness of the anti-discoloration film, discoloration due to partial peeling, occurrence of oxidation, corrosion, oil, etc. Dirt, foreign matter, etc. are removed, and the plating surface is uniformly and sufficiently cleaned and activated, so uneven sulfiding treatment is completely prevented, and the gloss of the plating surface increases, improving the quality of the sulfiding treatment. Product value is increased.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the concentration of the treatment liquid and the treatment time required to eliminate the discolored pattern on the surface of the steel plate.

Claims (1)

[Claims] (1) Prior to sulfurizing the copper-plated surface of a copper-plated steel sheet, acid treatment is performed using a hydrochloric acid aqueous solution or sulfuric acid aqueous solution with a concentration of 0.5 to 10%, and (a) an organic solvent with a concentration of 1 to 10%. (b) alkaline treatment using an aqueous sodium hydroxide solution or aqueous ammonia solution with a concentration of 0.5 to 5%; (c) buffing treatment using a buff of #150 or higher. 1. A pretreatment method for electrolytic copper-plated steel sheet with excellent sulfurization properties, characterized by performing one or more types of treatments.