JPH06915B2 - Pretreatment composition containing S-triazine compound - Google Patents

Abstract

The invention relates to an aqueous pretreating composition for application to a metal surface, characterised in that said composition has a pH of about 3.4 to 6.0 and comprises at least about .01 percent by weight based on the total weight of the composition of an S-triazine compound having at least one hydroxyl group on a carbon atom of the triazine ring. The invention also provides a process of pretreating a metal surface characterised by applying to the metal surface at a temperature of 30<o>C to 80<o>C an aqueous composition having a pH of about 3.4 to 6.0, said composition comprising at least 0.01 percent by weight based on the total weight of the composition of an S-triazine compound having at least one hydroxyl group on a carbon atom of the triazine ring. Preferably, the aqueous composition of the S-triazine compound is employed as a final rinse over a metal surface comprising a conversion coating such as a phosphate conversion coating.

Description

Description: FIELD OF THE INVENTION The present invention relates to a chromic acid-free pretreatment composition, which is particularly useful in the final rinse step of the metal pretreatment step.

(Prior art) In the metal pretreatment process, usually a final rinse (ri
phpsphating conversion c prior to the nsing or final sealing step.
It is well known that the oating process is used. Rinse compositions usually include chromic acid. While this chromic acid is effective in the rinse step, it is not desirable due to its toxicity and its associated disposal problems.

Therefore, various studies have been conducted to find chromic acid substitutes in the final rinse step. The present invention provides a pretreatment composition that is essentially free of chromic acid.

(Summary of the Invention) According to the above facts, the present invention contains an S-triazine having at least one hydroxyl group on a carbon atom in a triazine ring (hereinafter, referred to as "S-triazine compound"), Includes aqueous compositions used for surface pretreatment of ferrous or non-ferrous metals. The aqueous composition of the S-triazine compound has an S-content of at least about 0.01% by weight or more based on the total weight of the composition at a pH of about 3.4-6 and a temperature range of about 30-80 ° C. A triazine compound is included.

The present invention further includes a method of applying an aqueous solution composition of an effective S-triazine compound to a metal surface to produce a corrosion resistant surface to which subsequently applied paint can adhere. Preferably, the aqueous solution composition of the S-triazine compound is used as a final rinse composition for a metal surface containing a modified coating such as a phosphoric acid modified coating.

(Structure of Invention) The S-triazine compound or its derivative useful herein is
It is enolized by acidifying an aqueous solution composition containing them. Without being bound by any particular theory, enol-type S-triazine compounds are believed to have metal surface reactivity. The enol form of the preferred S-triazine compounds is commonly referred to as cyanuric acid. According to the invention, the S-triazine compounds and their derivatives useful herein are characterized by having at least one hydroxyl group on a carbon atom in the triazine ring.

Useful S-triazine compounds must be compatible with aqueous media. That is, it mixes with water to form an effective aqueous composition that produces a corrosion resistant surface that can be applied to a substrate and to which subsequently applied paint can adhere. Typically at least about 0.01 / 100g water at 25 ° C
It must have a solubility of g. The aqueous composition of the present invention is preferably at a temperature of about 30-80 ° C, more preferably about 30 ° C.
It is prepared by mixing the S-triazine compound with an aqueous medium at a temperature of 40-80 ° C. The aqueous medium is water, or
It means water in combination with an auxiliary agent which can enhance the solubility of the S-triazine compound. Aqueous compositions also include pH buffers, phosphoric acid, boric acid, potassium salts and the like or mixtures thereof.

Thus, the aqueous pretreatment composition of the present invention may have a pH in the range of about 3.4-6, preferably about 4.0-5.0. The composition comprises the S-triazine compound in an amount of about 0.01-0.2% by weight, preferably about 0.05-0.15% by weight, based on the total weight of the composition.
May be included. Although it is possible to include a larger amount of S-triazine compound in the aqueous composition, it is considered that such a composition does not improve the performance. However, under certain circumstances, higher concentrations in the form of concentrates may be desirable for reasons such as ease of handling.

The aqueous composition of the S-triazine compound is produced by a conventional coating process,
Alternatively, it is applied under conditions that produce an acceptable corrosion resistant protective wall in subsequent coating processes, such as electrolytic coating processes. The temperature of the aqueous composition when the substrate is treated is typically about 30-80 ° C, preferably about
40-60 ° C. The pH of the treatment composition during coating is typically about 3.5-6, preferably about 4-5.0.

In the process of the present invention, the aqueous composition of S-triazine compound is used for treating ferrous or non-ferrous metals such as cold rolled steel and galvanized steel. Preferably, the aqueous composition is a phosphoric acid modified coating, where a zinc phosphate modified coating is preferred.
Applied to a metal surface consisting of a modified coating such as. The aqueous composition containing the S-triazine compound is applied to the metal surface by spraying, dipping or any other suitable method. After the aqueous composition has been applied, the metal is usually rinsed with deionized water, dried and then coated with a surface coating.

In a typical pretreatment process, the metal to be treated is cleaned by chemical or physical means to remove surface stains such as grease and dust, and rinsed with water. The metal surface is then contacted with the modified coating composition, rinsed with water and then rinsed with the composition of the invention. After application of the aqueous S-triazine compound solution by rinsing and drying, the ferrous or non-ferrous metal may be coated by any suitable method. It has been found that the pretreatment step of treating the metal with the aqueous composition of the S-triazine compound imparts excellent adhesion and corrosion resistance to the coated substrate.

EXAMPLES The present invention will be further described below with reference to non-limiting examples.

Example 1 CHEMFOS hot dipped galvanized steel sheet
Phosphorylation was performed using a 710 zinc / nickel / manganese phosphorylation solution (Chemfil) at an average coating weight of 270 mg / ft ² . The steel sheet was rinsed with water to remove residual phosphorylating agent and then immersed in an aqueous cyanuric acid solution at 120 ° F for 30 seconds. Two concentrations of cyanuric acid solution were used, 0.1 and 0.2% cyanuric acid in city water. The measured pH was 4.0 and 3.4, respectively. The steel plate was dried with a compressed air jet, and on the same day, about 240 ED3150W electrodeposited primer (manufactured by PPG Industry Co., Ltd., referred to as “PPG”)
Bolt primed to give a 1.2-1.6 mil thick dry film. Then, the steel plate was coated with HUBC 90270 white base coat (PPG
Co.) to a thickness of about 0.9 mil and URC 1000 clear coat (PPG) to a thickness of about 1.9 mil. Then, for scribing and abrading tests with steel shots according to the "CHRYSLER" chipping scab test method as follows:
A test piece was prepared from this steel plate.

1) A 4 ″ × 12 ″ test steel plate was coated as described above.

2) The upper half of the steel plate was engraved with a 12 cm (4.7 ″) “X” scribe. A piece of tear tape was firmly attached to one side of "X" and quickly moved vertically to remove. This process was repeated for the other "X".

3) Adjust the air pressure of the gravelometer (Q-Panel) to 205 kPa
(30 psi).

4) Shut off the gravelometer air valve and collect 200 ml (32 oz) of steel shots.

5) The test steel plate was attached to the panel holder with the coated surface facing the gravel injection mechanism of the gravelometer. The test chamber door was then closed.

6) The air valve was opened to stabilize the pressure. 200 ml (32 ounce)
I poured the shots of No. 3 into the hopper. After consuming all the shots, the air was shut off.

From 15 to 7) steel plate in a 5% salt solution (pH about _{6.6 to 7.1)}
I left it for a minute.

8) The steel sheet was taken out, allowed to recover for 1 hour and 15 minutes under laboratory conditions, and placed in a thermostat for 22.5 hours.

The "acceleration" test was performed as follows: a) The thermostatic chamber was set at 85% relative humidity and 60 ° C (140 ° F).

b) The repeating steps outlined in steps 7 and 8 were continued for 4 days.

c) After that (fifth day), remove the panel from the thermostat and
The above steps 3 to 8 were performed within 30 minutes.

d) At the end of steps a to c of the 5 week cycle (after step 6), the steel plate is sponge and water (a mild surfactant can be used).
Washed with. Excess water was removed and the steel sheet was allowed to recover for 30 minutes.

e) The target area was covered with peel tape and removed as described in step 2 above.

f) The paint loss ratio in the target area was calculated.

Control: CHEMSEAL 20 chrome rinse (Chemfil) and deionized water rinse control steel sheets were prepared for comparison. 3 test steel plates were prepared for each system, and CHRYSLER chipping scale was used as above.
It was submitted to the test. The entire test period was 10 weeks. Panels were taped with # 898 3M SCOTCH tape after the test period and evaluated by the amount of paint removed. The test results are shown in Table I below.
It is described in.

Example 2 Cold rolled steel (CRS) plate and hot dip galvanized steel (HDG) were phosphorylated to about 230 mg / ft ² using CHEMFOS 86 zinc-nickel phosphate (Chemfil). After rinsing with water, the steel sheet was immersed in a 0.1% solution of cyanuric acid at 120 ° F and pH 4.1 for 30 seconds.

A control for comparison was made by performing a CHEMSEAL 20 chrome rinse and a deionized water rinse.
These specimens were rinsed with deionized water, dried with a compressed air jet, and then UNI-PRIME electrocoat (PPG
Was applied to cold-rolled steel at 240 volts to a thickness of 1.2 mil. The steel sheet was overcoated with a HUBC 90270 white basecoat to a thickness of 1.0 mil and a URC 1000 clearcoat to a thickness of 1.6 mil. Three steel plates were prepared for each test, and the tests were performed according to the CHRYSLER chipping / scab test method described in Example 1. The test results are reported in Table II below.

Example 3 Heavy gauge hot rolled steel was pretreated with CHEMFOS 86 zinc-nickel phosphate coating to a thickness of about 240 mg / ft ² ,
Rinse with water and soak for 30 seconds in a 0.1% aqueous composition of cyanuric acid at 120 ° F. The steel sheet is rinsed again with water, dried with compressed air, and then ED 4201 black electrostatic coating primer (PPG
Co., Ltd.) to a dry thickness of about 0.8 mil.

CHEMSEAL 20 Control steel sheets were made by chrome rinse and deionized water rinse. Three steel plates were prepared for each system and tested for 8 weeks in essentially the same manner as described in the CRYSLER cab test cabinet.
The test results are reported in Table III below.

a) The apparent numerical rank of this test is based on the 0-10 criteria. 10 indicates no defects and 0 indicates gross defects due to rust with swell, which were initially not visible and apparent.

Although embodiments of the present invention have been described above, various modifications of the present invention will be obvious to those skilled in the art, and can be implemented by those skilled in the art without departing from the scope and spirit of the present invention. Accordingly, the claims directed to the invention are intended to cover all aspects of the invention that are considered equivalent by those skilled in the art to which the invention pertains.

Claims (14)

[Claims] 1. An S-triazine compound having a pH of about 3.4 to 6.0 and having at least one hydroxyl group on a carbon atom in the triazine ring is at least about 0.01 weight% based on the total weight of the composition. %, Aqueous pretreatment composition for application to metal surfaces. 2. The aqueous composition according to claim 1, wherein the S-triazine compound is cyanuric acid. 3. The aqueous composition of claim 1 having a pH of about 4-5.0. 4. The aqueous composition of claim 1, wherein the S-triazine compound is present in an amount of about 0.05 to 0.15% by weight based on the total weight of the aqueous composition. 5. The aqueous composition of claim 1, wherein the temperature of the composition is about 30-80 ° C. 6. An S-triazine compound having a pH of about 3.4 to 6.0 and having at least one hydroxyl group on a carbon atom in the triazine ring is at least about 0.01 weight% based on the total weight of the composition. %, Applying an aqueous composition containing 30% to a metal surface at a temperature of about 30 to 80 ° C. 7. The process according to claim 6, wherein the S-triazine compound is cyanuric acid. 8. The process of claim 6, wherein the pH is about 4-5.0. 9. The process of claim 6 wherein said S-triazine compound is present in an amount of about 0.05-0.15% by weight based on the total weight of the composition. 10. The process of claim 6 wherein the metal surface comprises a phosphoric acid modification coating. 11. The process of claim 10 wherein the modified coated metal surface comprises a zinc phosphate coating. 12. An article comprising a pretreated metal surface produced by the process of claim 6. 13. An article comprising a pretreated metal surface produced by the process of claim 10. 14. An article comprising a pretreated metal surface produced by the process of claim 11.