JPS5919194B2 - Surface treatment method for zinc or zinc alloy coated steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for zinc or zinc alloy plated steel sheets, and in particular, to provide a surface treatment method for zinc or zinc alloy plated steel sheets that is harmless, does not contain chromium, has excellent corrosion resistance, and has good paint adhesion. , relates to a surface treatment method that can quickly produce a coating with good corrosion resistance after painting.

Zinc or zinc alloy plated steel sheets are subjected to surface treatment methods for the purpose of improving the corrosion resistance of the surface, paint adhesion, and corrosion resistance after painting.

Conventionally, such surface treatment methods include (1) chromic acid;
A method using chromate or various treatment liquids containing these as the main ingredients, a method using a treatment liquid containing nitrate phosphate as the main ingredient, and (3) a method using a treatment liquid containing phytate as the main ingredient. etc. In method (1), immersion treatment or electrolytic treatment is widely used in these methods, and is an excellent method for improving the corrosion resistance of the surface of zinc or zinc alloy plated steel sheets, paint adhesion, and corrosion resistance after painting. Also,
Method (2) has an excellent effect on improving paint adhesion and corrosion resistance of steel sheets surface-treated after painting, and method (3) is a harmless treatment that does not contain harmful metals such as chromium. The effect of this treatment is to provide a surface coating with excellent corrosion resistance, paint adhesion, and post-painting corrosion resistance. However, since these methods &L(1) use chromium compounds, there are problems in terms of workability, wastewater treatment, product handling, etc.

In the method (3), corrosion resistance is poor if the product is not painted or if the storage period before painting is long, and the treatment time is long for steel plates that have been A-plated using method (3).
Moreover, it has better corrosion resistance than those treated immediately after plating.
It has five drawbacks: poor paint adhesion and poor corrosion resistance after painting. The present inventors have demonstrated that steel sheets that have been subjected to zinc or zinc alloy plating for a long period of time can be surface-treated in a time comparable to that of surface treatment of steel sheets immediately after plating, and that corrosion resistance and
In order to obtain a surface treatment effect with excellent paint adhesion and corrosion resistance after painting, we investigated a treatment liquid containing phytic acid as the main component.

As a result, the inventors discovered that the above object could be achieved by treating with a treatment solution containing a metal salt of phytic acid and polyamines, and completed the present invention. That is, 0.1 to 25% by weight of one or more metal salts of phytic acid of the present invention &A and 0.1 to 25% by weight of one or more polyamines.
This is a surface treatment method for zinc or zinc alloy plated steel sheets, which is characterized by treating with a treatment liquid containing 0.001 to 5% by weight.

The metal salts of phytic acid used in the method of the present invention include alkali metal salts, alkaline earth metal salts, zinc salts,
These include nickel salts and cobalt salts, and may also be double salts thereof.

The equivalent ratio of phytic acid to metal ions and alkali metal ions is 1:1 to 1:12 for phytic acid to metal ions, and 1:1 to 1:6 for other than alkali metal ions. These metal salts of phytic acid can be easily obtained by dissolving oxides, hydroxides, phosphates, carbonates, and nitrates of the metals in an aqueous solution of phytic acid.

Furthermore, two or more of these metal salts may be used in combination.
Polyamines used in the method of the present invention and the general formula (1) A
+HNCH2CH2NH+NB (1) (wherein A and B represent hydrogen or a 3-aminopropyl group, and n is an integer of 1 to 10), such as ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylene hexamine, 2-aminoethyl-3-aminopropylamine, 4,
7-diazadecane-1,10-diamine and the like.

These polyamines may be used alone or in combination of two or more. The content of the treatment liquid used in the method of the present invention varies depending on the type of metal salt of phytic acid and polyamines used, but usually one or more metal salts of phytic acid are contained in the treatment liquid. 0.1-25% by weight, 0.001:-5% by weight of one or more polyamines
The content of the metal salt of phytic acid in the treatment solution is as follows: an aqueous medium may be used as the solvent, and an organic solvent that dissolves in water may be included, but water is particularly preferred from the viewpoint of solubility. If the polyamine content is less than 0.1% by weight and the content of polyamines is less than 0.001% by weight, sufficient effects may not be obtained because the treatment time may be long or the surface treatment film may be incomplete. do not have.

Furthermore, when the content of metal salts of phytic acid in the treatment liquid reaches 25% by weight and the content of polyamines reaches 5% by weight, the effects of the present invention are fully achieved, and treatment liquids with higher concentrations are less expensive. This is uneconomical and undesirable as it increases the cost.

It is preferable to adjust the treatment liquid to below PHLO.
If the content exceeds 0, the corrosion resistance of the surface treatment film decreases. The pH may be adjusted by using only a metal salt of phytic acid and an amine, or by using phosphoric acid, oxalic acid, tartaric acid, citric acid, malic acid, etc. Process for treating zinc or zinc laminated steel sheets with the treatment solution of the present invention fζ Using a treatment bath in the range of room temperature to 90°C, immersion treatment for a short time (0.5 to 25 seconds, preferably 1 to 10 seconds), Alternatively, apply a coating treatment such as a spray treatment or a roll coater treatment, and then remove excess residual liquid using a known wiping means such as a rubber roll or high-pressure gas, and dry at a temperature of 40 to 330°C, preferably 11ζ70 to 200°C. It performs heat treatment. In this treatment method, the drying and heat treatment steps are particularly important. If the insolubilization reaction of the treated film in this step is not sufficient, the corrosion resistance will be poor, and if left after painting and baking, there will be minute blisters (blisters) on the entire painted surface. 1) occurs, and the adhesion of the paint and the corrosion resistance after painting are significantly deteriorated.

In the treatment method of the present invention, even if a steel plate has been plated with zinc or zinc alloy for a long time (for example, 2 days or more), it can be immersed in a short time or coated with a solution using a spray, roll coater, etc. to improve corrosion resistance and paint. A surface treatment film with better adhesion and post-painting corrosion resistance than those using conventional taromic acid-based or inorganic phosphate-based surface treatment liquids can be obtained.
Further, even if the steel sheet has just been subjected to zinc or zinc alloy plating treatment, a surface treatment film having excellent corrosion resistance, paint adhesion, and post-painting corrosion resistance can be obtained by surface treatment. Examples and comparative examples are shown below. Example 1 Thickness 0.8v! Electrolyze T cold rolled steel sheet in sodium orthosilicate aqueous solution? After lying down and pickling in an aqueous sulfuric acid solution, the amount of plating per side was 20V/1 using an acidic zinc electroplating bath.
d electrogalvanizing was carried out.

The electrogalvanized steel sheet thus produced was left in the atmosphere for one week. After this, it was immersed in a treatment solution consisting of 255.6 r of a 50% aqueous solution of phytic acid/Kfl, 32.6 f of potassium hydroxide/22.5 t of Kfl, remaining water at 70°C, and then withdrawn. Squeeze excess processing liquid with a roll, dry at 100℃ for 7 seconds,
Heat treatment was performed. Example 2 Using a cold-rolled material with a thickness of 1.2 mm, hot plating was carried out using a non-oxidizing furnace method.
Zn-7.5% Al alloy plating was performed at a plating amount of 75 f/M2 per side.

The heat soaked Zn-Al alloy plated steel sheet thus produced was left in the atmosphere for 5 days. After this, this was mixed with 154 ft/K9 of a 50% aqueous solution of phytic acid and 4 ft/4 of sodium hydroxide.
2V/Kfl triethylenetetramine 5t/Kfl oxalic acid 29t/KKfl balance water
The sample was immersed at 150°C for 4 seconds and pulled up, and then the excess treatment liquid was squeezed out using a roll, and the sample was dried and heat-treated at 150°C for 3 seconds. Example 3 Using a cold-rolled material with a thickness of 0.4 μm, hot-dip galvanizing was performed at a plating amount of 150 t/M 2 per side by the Sendzima method.

The hot galvanized steel sheet thus produced was left in the atmosphere for one week. After this, 13.2t/! of a 50% aqueous solution of phytic acid was added to the solution. , cobalt nitrate 17.4t/Kfl2
-Aminoethyl-3-aminopropylamine 1V/Kg
, immersed in a treatment solution consisting of 3.5y/Kfl of 85% phosphoric acid and the remainder water at 50℃ for 3 seconds, then pulled up, then squeezed out the excess treatment solution with a roll, dried at 80℃ for 6 seconds, and heat-treated. Ta. Example 4 Thickness 1.271J! A cold-rolled steel sheet was electrolytically degreased in a sodium orthosilicate aqueous solution, then pickled in a sulfuric acid aqueous solution, and then electroplated to a plating amount of 10 V/Df on one side.
) Zn-40%Sn alloy plating was performed.

The electrical Zn-Sn alloy plated steel sheet thus produced was left in the atmosphere for 3 days. Thereafter, this was mixed with 159f/Kf of a 50% aqueous solution of phytic acid and basic nickel carbonate 4
5.3t/Kfl4.7-Diazadecane-1.10-diamine 20V/V4 Tartaric acid 2f/Kf, the remainder was sprayed with a treatment bath at room temperature for 5 seconds, and after squeezing with a roll, dried at 160°C for 3 seconds. Heat treatment was performed. Example
5 A cold-rolled steel sheet with a thickness of 0.8 μ was electrolytically degreased in an aqueous sodium hydroxide solution, then pickled in an aqueous hydrochloric acid solution, and then plated at a plating amount of 20 f/M per side using an acidic zinc electroplating bath.
2 electrogalvanizing was carried out.

The electrogalvanized steel sheet thus produced was left in the atmosphere for 10 days. After this, this was mixed with a 50% aqueous solution of phytic acid 365.61/Kg and zinc oxide 225y/! , pentaethylenehexamine 2f/Kg, balance water 80
After being immersed in a treatment bath at 180°C for 1.5 seconds and withdrawn, the excess treatment solution was squeezed out using high-pressure air, and drying and heat treatment were performed at 180°C for 4 seconds. Example 6 After leaving the electrogalvanized steel sheet prepared in Example 5 in the atmosphere for one month, it was treated with 50% phytic acid.
% aqueous solution 92.2V/V-f1 Magnesium hydroxide 10
．． 2V/Vifl diethyl triamine 2.5V/! ,
Using a 50° C. treatment bath consisting of water in the balance, the treatment bath was applied with a roll coater, and then a dry heat treatment was performed at 190° C. for 3 seconds.

Examples 7 to 9 Electrogalvanized steel sheets prepared in the same manner as in Example-1 were left in the atmosphere for one week, and then immersed in a treatment solution with the composition shown in Table 1 under the conditions shown in Table 1. Excess processing liquid was squeezed out using a roll, and the sample was dried and heat-treated at 100° C. for 10 seconds.

Comparative Example 1 The electrogalvanized steel sheet prepared in Example 1 was left in the atmosphere for one week, and then treated and dried under the same conditions using a treatment bath with the same composition as that used in Example 1 except for ethylenediamine. Heat treatment was performed.

Comparative Example 2 Heat crushed Zn-A prepared in Example 2! After the alloy-plated steel sheet was left in the atmosphere for 5 days, it was treated, dried, and heat treated under the same conditions as in Example 2 using a treatment bath with a composition other than triethylenetetramine.

Comparative Example 3 The hot crushed galvanized steel sheet prepared in Example 3 was left in the atmosphere for one week, and then treated using a treatment bath with a composition other than the treatment bath used in Example 3 except for 2-aminoethyl-3-aminopropylamine. , treatment, drying, and heat treatment were performed under the same conditions.

Comparative Example 4 After leaving the electric Zn-Sn alloy plated steel sheet prepared in Example 4 in the atmosphere for 3 days, it was exposed to the treatment baths 4 and 7 of the treatment bath used in Example 4.
Using a treatment bath with a composition other than -diazadecane-1,10-diami Z, treatment, drying, and heat treatment were performed under the same conditions.

Comparative Example 5 The electrogalvanized steel sheet prepared in Example 5 was exposed to air for 10 minutes.
After being left for one day, treatment, drying, and heat treatment were carried out under the same conditions as in Example 5, using a treatment bath with a composition other than pentaethylenehexamine.

Comparative Example 6 The electrogalvanized steel sheet prepared in Example 5 was left in the atmosphere for one month, and then treated and dried under the same conditions using a treatment bath with the composition used in Example 6 except for diethylenetriamine. , heat treatment was performed.

Comparative Examples 7 to 12 Zinc or zinc alloy plated steel sheets were subjected to chromic acid treatment.

Comparative Example 13 After the electrogalvanized steel sheet prepared in Example 1 was left in the atmosphere for one week, 50% of the phytic acid in the treatment bath used in Example 1 was removed.
Treatment, drying, and heat treatment were performed under the same conditions using a treatment bath with a composition excluding the % aqueous solution and potassium hydroxide.

Comparative Example 14 The heat soaked Zn-Al alloy plated steel sheet prepared in Example 2 was left in the atmosphere for 5 days, and then the composition of the treatment bath used in Example 2, excluding the 50% aqueous solution of phytic acid and sodium hydroxide, was Using a treatment bath with the same composition, treatment, drying, and heat treatment were performed under the same conditions.

Comparative Example 15 The hot-soaked galvanized steel sheet prepared in Example 3 was left in the atmosphere for one week, and then treated using a treatment bath with a composition other than the 50% aqueous solution of phytic acid and cobalt nitrate of the treatment bath used in Example 3. Treatment, drying, and heat treatment were performed under the same conditions.

Comparative Example 16 After leaving the electric Zn-Sn alloy plated steel sheet prepared in Example 4 in the atmosphere for 3 days, a 50% aqueous solution of phytic acid in the treatment bath used in Example 4 was prepared, except for basic nickel carbonate. Using a treatment bath, treatment, drying, and heat treatment were performed under the same conditions.

Comparative Example 17 The electrolytic galvanized steel sheet prepared in Example 5 was exposed to air for 10 minutes.
After standing for several days, 5% of phytic acid in the treatment bath used in Example 5 was added.
Treatment, drying, and heat treatment were performed under the same conditions using a treatment bath with a composition excluding the 0% aqueous solution and zinc oxide.

Comparative Example 18 After the electrogalvanized steel sheet prepared in Example 5 was left in the atmosphere for one month, 50% of the phytic acid in the treatment bath used in Example 6 was removed.
% aqueous solution and a treatment bath with a composition excluding magnesium hydroxide, treatment, drying, and heat treatment were performed under the same conditions.

Comparative Examples 19 to 22 Electrogalvanized steel sheets prepared in the same manner as in Example-1 were left in the atmosphere for one week, and then immersed in a treatment solution having the composition shown in Table 2 under the conditions shown in Table 2. Thereafter, the excess treatment liquid was squeezed out using a roll, and the sample was dried and heat-treated at 100° C. for 10 seconds.

The following tests were conducted on the treated steel sheets obtained in the above Examples and Comparative Examples.

Claims (1)

[Claims] 1 One or more metal salts of phytic acid at 0.1
~25% by weight, and general formula (I)A■HNCH_2
One or two polyamines represented by CH_2NH■_nB(I) (wherein A and B represent hydrogen or a 3-aminopropyl group, and n is an integer of 1 to 10)
1. A method for surface treatment of zinc or zinc alloy plated steel sheets, characterized by treating with a treatment liquid containing 0.001 to 5% by weight of zinc or zinc alloy plated steel sheets.