JP2529787B2 - Steel plate surface damage repair method - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a damage-repairing techniques galvanized steel sheet, in particular, to a technique for improving the adhesion of putty used for repairing of the self <br/> dynamic exterior plate for galvanized steel.

[0002]

Most automobile and truck skins are
Made of mild steel. Steel consists of an alloy containing iron as a main component and a small amount of carbon as a main alloying component. This alloy, more precisely called carbon steel, accounts for over 90% of the steel produced worldwide.

The carbon content of low carbon steel called mild steel is
It is usually 0.25% or less. Low carbon steels are easy to heat treat and are widely produced as beams (girders) and other construction materials.

Medium carbon steel having a carbon content of 0.25 to 0.70% is best used for machine parts which require high strength and good fatigue resistance. High carbon steel has a high carbon content
It is over 0.7%, and because of its high hardness and low toughness, it belongs to a special field.

Dimples or grooves formed on the surface of an automobile skin by using a putty made of a thermosetting resin such as an unsaturated polyester resin or an epoxy vinyl ester resin, a filler, an accelerator, a catalyst and other additives. It is well known to repair injuries. The putty is required to be stiff and then capable of being shaped to match the shape of the vehicle skin.

[0006] A general outer plate putty has been often used for repairing damage on the surface of an automobile outer plate. However,
Rust and corrosion are becoming increasingly problematic for automobiles whose skins are made of mild steel.

In order to prevent corrosion as much as possible, the automobile industry is considering using zinc-coated steel sheets or galvanized steel sheets instead of mild steel. However, it is known that putty suitable for mild steel has poor adhesion to galvanized steel sheets.

Therefore, there is an urgent need to improve the adhesiveness of the putty to the galvanized steel sheet.

US Pat. No. 4,525,427 (Bayha et a
l) relates to a thin-film moldable polyester composition that adheres to a metal or plastic substrate and is used especially for repairing automobile skins. This composition is called "body putty primer". Bayha also says that the metal surface may be chemically etched to enhance the adhesion of the repair agent to the metal surface.

US Pat. No. 4,531,275 (Kelly)
Disclosed is a method of repairing an automobile outer plate damaged by rust or an accident. This method is a method in which a metal patch is applied from the back side to a hole formed by removing a damaged portion using a fastener. The body filler is filled in the recess formed on the back side of the opening. A galvanized steel plate is used for the metal patch.

US Pat. No. 4,732,633 (Pokorny)
Discloses a method of repairing the surface of a damaged skin with a corrosion resistant patch. In this method, the back side of the patch contacts the damaged surface and adheres to the metal portion adjacent the damaged surface.

US Pat. No. 4,148,122 (Phillips)
Relates to a method for repairing automobile outer panels damaged by rust, in which holes or cavities formed on the back side of rust are shaped, a moldable plastic material is embedded therein, and then a polyester resin filler is applied. This is a method in which the surface of the filler is shaved and then shaped so as to match the surface shape of the automobile outer plate.

US Pat. No. 2,150,929 (Kohler)
Disclosed is a method for protecting a galvanized steel sheet which has been deformed to the extent that cracks and peeling occur in the plated film. This method uses mercury amalgam to form a protective coat on the deformed portion.

US Pat. No. 4,308,118 (Dudgeon)
Discloses a mineral-filled epoxy resin composition that is cured by heat and UV irradiation.

US Pat. No. 2,886,420 (Troy et al)
Discloses a method and apparatus for maintaining the activity of an iron chloride etching bath used for etching metals such as copper, tin, aluminum and zinc.

US Pat. No. 3,726,707 (Prosser et.
al) relates to the pretreatment of steel when enamel is primed or overcoated.

US Pat. No. 3,824,136 (Gilbert)
Discloses a chemical milling method for flowable aluminum wafers. This method has a step of spraying an etching solution composed of iron chloride, hydrochloric acid and water on a thin aluminum plate.

US Pat. No. 4,482,426 (Maynard et
al) discloses a method of forming openings in a nickel-iron alloy piece by etching with an iron chloride etchant.

US Pat. No. 4,567,067 (Keal) discloses a method of treating an aluminum surface in a enamel process. This method uses an iron sulfate aqueous solution as an etching solution.

US Pat. No. 3,957,669 (Tulsi et a
l) discloses a chemical etching method for steel which is carried out in the pre-step of the metal plating process which can be coated with enamel.

[0021]

SUMMARY OF THE INVENTION The present invention is based on the discovery that chemical etching of galvanized steel surface improves the adhesion of polyester resins used in automotive exterior repair putty.

An object of the present invention is to provide a technique capable of improving the adhesiveness of a putty for repairing an automobile outer panel made of a galvanized steel sheet.

[0023]

DISCLOSURE OF THE INVENTION According to the present invention, when a putty based on a polyester resin is used to repair damage to the surface of an automobile outer plate made of a galvanized steel sheet, a metal that is more positive than zinc is used in advance. The surface of the outer plate is chemically etched with an etching solution containing salt. The putty is applied to the etched skin surface, and after curing, shaped to match the shape of the skin surface.

Metals that are more electropositive than zinc include iron, cadmium, nickel, lead, tin, copper, silver, mercury, platinum and gold. Metal salts are prepared from mineral or organic acids in which these metals are soluble.

As the metal salt used in the etching solution, iron salts such as ferrous sulfate, ferrous chloride and ferric chloride are preferable, and among them, ferric chloride is particularly preferable because of its high solubility.

Most of the compositions of conventional etching solutions for removing rust are phosphoric acid, acetic acid and similar acids. The etching with acid takes a long time and cannot be easily performed, so that it is not useful for an automobile repair shop requiring immediate effect.

On the other hand, the etching composition of the present invention containing a neutral metal salt is easily accepted in an automobile repair shop because of its quick reaction. Furthermore, etching with a neutral metal salt is more easily accepted from the viewpoint of environment and safety, and stronger adhesiveness is obtained than etching with an acid.

When a galvanized steel sheet is treated with a ferric chloride solution, a dark gray layer of iron is formed within 1 minute by the following reaction.

3Zn + 2FeCl ₃ → 3ZnCl ₃ + 2Fe As shown in the above chemical formula, the zinc element plated on the steel plate is replaced with the iron element.

It is necessary to adjust the concentration of the etching solution and the etching time so that the zinc plating layer is not completely removed. These parameters depend on the thickness of the galvanized layer. The upper limit of the concentration of the etching solution is a saturated solution of a metal salt used as an etchant.

Since iron and zinc have different appearances, it is relatively easy to distinguish them visually. Iron forms a dark and dense layer and has excellent adhesion to both the zinc layer and the putty. When an automobile exterior plate repair putty based on an unsaturated polyester resin was applied to the above-mentioned etched surface, excellent adhesion was obtained.

Chemical etching for a general steel plate is
Although the adhesion of the putty is improved to some extent, there is a difference between success and failure in the apparent improvement effect of the adhesion of the putty for automobile outer panel to the galvanized steel plate.

The degree of etching is adjusted depending on the concentration and amount of the ferric chloride solution used. In order not to impair the corrosion resistance, the etching should be controlled so as not to completely remove the galvanized layer of the steel sheet.

Further, the etching is further promoted by adding about 1 to 10 g of phosphoric acid such as orthophosphoric acid to 100 g of water used for the etching solution containing a small amount of acid, for example, a saturated amount of ferric chloride. Was found.

Even if the galvanized layer is completely removed from the steel sheet by the above etching, the adhesion is still improved because the steel under the galvanized layer is etched by ferric chloride according to the following equation: It

Since Fe + 2FeCl ₃ → 3FeCl ₂ ferrous chloride is water-soluble, it can be removed by washing the etching surface to which the putty is applied with water.

The etched surface is washed with water and then dried, and a putty for repairing an automobile outer panel, which is based on an unsaturated polyester resin, is applied. No primer or other pretreatment is required.

The putty has a thermosetting resin (preferably,
(Contains an accelerator for unsaturated polyester resin)
And a filler mainly composed of talc. Also, a vinyl ester resin can be used. A typical example of a preferred composition of an automobile exterior plate putty based on an unsaturated polyester resin is described in the above-mentioned Bayha US Pat.
No. 525427.

Next, examples of the present invention will be described.
Unless otherwise specified, parts and% are by weight.

[0040]

Embodiment 1 A. Preparation of Resin 0.25 mol of maleic anhydride, 0.75 mol of phthalic anhydride and 1.05 mol of diethylene glycol were esterified at 215 ° C. until the acid value was 28 or less. After cooling, hydroquinone 80ppm and parabenzoquinone 25ppm
Was added and styrene was added until the amount thereof became 30% of the whole to prepare a liquid resin. This was designated as "resin A".

B. Preparation of Putty for Repairing Automotive Skins Putty for repairing automobile skins having the following composition was prepared.

Composition parts by weight Resin A 39.712 1,4-naphthoquinone 0.004 Cobalt-2-ethylhexoate (Co 12%) 0.024 N, N-dimethylaniline 0.026 Powder talc 60.00 Benzoyl peroxide 2 g of 50% paste (also called dibenzoyl peroxide) was added as a catalyst to 100 g of the above putty to give a gel time of about 4 to 6 minutes.

C. Preparation of Etching Solution An etching solution was prepared by dissolving 80 g of anhydrous ferric chloride in 100 g of distilled water.

D. Galvanized steel sheet General "20 Gauge" Galvanized steel sheet (actual thickness 0.038
Inch) was cut into 3 × 8 inch to obtain a test panel.

E. General Steel Plate A general "20 Gauge" steel plate (actual thickness 0.032 inch) was cut into 3 x 8 inches to prepare a test panel.

[0046]

Second Embodiment-Surface Treatment-A. General Steel Plate, Polishing A test panel made of a general steel plate was polished with # 80 sandpaper and then wiped off with an acetone-impregnated paper towel.

B. General steel plate, etching In the same manner as above, a test panel made of general steel plate is # 8.
After polishing with sandpaper of No. 0, it was wiped off with an acetone-impregnated paper towel. Example 1 on this test panel
The etching solution was applied with a brush, left for 45 seconds, and then washed with distilled water. After that, it was wiped off with a paper towel.

C. Galvanized Steel Plate, Polishing A test panel made of a galvanized steel plate was polished with # 80 sandpaper and then wiped off with an acetone-impregnated paper towel.

D. Galvanized Steel Sheet, Etching A test panel made of a galvanized steel sheet was polished with # 80 sandpaper and then wiped off with an acetone-impregnated paper towel. The test panel was brushed with the etching liquid of Example 1, left standing for 45 seconds, and then washed with distilled water. After that, it was wiped off with a paper towel.

A dark gray layer, identified as iron, appeared in this test panel. It was also confirmed that the galvanized layer remained under the iron layer.

[0051]

Example 3 -Adhesiveness of putty to metal surface-A. Heat Resistance A 3 × 8 inch test panel treated with Example 2 was treated as follows.

Putty 100 for repairing automobile skins of Example 1B
g and 2 g of a catalyst composed of a benzoyl peroxide 50% paste were mixed, and this was 2 × 5 inches and a thickness of 0.01
It was applied to a metal surface by using a doctor blade so that it became inch.

FIGS. 1 (a) and 1 (b) are side views of a test panel 2 to which the above-mentioned automobile exterior plate repair putty 4 is applied.

The putty began to cure after 4-5 minutes at room temperature. After curing at room temperature for 24 hours, at 105 ° C for 3 hours
Allowed to cure for hours. Furthermore, after leaving it at room temperature for 24 hours, the test panel was bent 90 degrees. The adhesion failure point 6 shown in FIG. 1 (b) which occurs after bending at 90 degrees is called a "gap".

The adhesiveness of the putty was evaluated by measuring the gap length of the putty peeled from the test panel when bent 90 degrees. In addition, the degree of adhesion of the putty layer remaining adhered to the test panel was also evaluated.

B. The test panels were treated as in A above, except that the moist heat resistant putty layer was 0.038 inches thick. After the putty was cured at room temperature for 24 hours, the test panel was immersed in distilled water at 95 ° C for 2 hours. The test panel was taken out of the distilled water, left to dry for 24 hours, and then subjected to the bending test.

The adhesiveness was evaluated as follows.

Excellent : The cap length is 0.5 inch or less. The remaining putty adheres to the test panel at the gap. Putty is firmly adhered to the test panels other than the gaps.

Good : Same as the above except that the cap length was 1.0 to 1.5 inches.

Acceptable : Same as above except that the cap length is 1.5 to 2.5 inches.

No : The putty was completely or almost completely peeled off.

The evaluation results are shown in Table 1 below.

[0063]

[Table 1]

In the above description, the case where the present invention is applied to the repair of an automobile outer plate has been described, but the application field of the present invention is wide, and it can be applied to repair any damage on the surface of a steel plate.

[0065]

According to the present invention, the adhesiveness of putty used for repairing the surface of a galvanized steel sheet can be markedly improved.

[Brief description of drawings]

FIG. 1 is a side view of a test panel to which a putty for repairing an automobile outer panel is attached, (a) is a side view before bending, and (b) is a side view after bending.

[Explanation of symbols]

 2 Test panel 4 Putty for repairing automobile outer panel 6 Poor adhesion (gap)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B05D 7/24 302 B05D 7/24 302V (56) Reference JP-A-57-53277 (JP, A) ) Japanese Patent Publication Sho 53-42023 (JP, B2) "Painting Technology Handbook" edited by Japan Coating Technology Association (SHO 62-2-27) Nikkan Kogyo Shimbun P. 669

Claims (5)

(57) [Claims] 1. A zinc membrane comprising the following steps (a) to (c):
Method of repairing damage on steel plate surface. (a) etching the galvanized steel sheet surface by applying an etching solution containing a water-soluble metal salt is Yodenki than zinc, (b) the etched galvanized steel sheet vinyl ester resin, A step of applying putty containing a resin selected from the group consisting of unsaturated polyester resins and mixtures thereof as a main component, (c) a step of curing and shaping the applied putty to finish repair. 2. The method for repairing damage on the surface of a galvanized steel sheet according to claim 1, wherein the galvanized steel sheet is an automobile outer panel. 3. The metal part of the water-soluble metal salt is ferrous iron, ferric iron, cadmium, nickel, lead, tin, copper, silver, mercury,
The method for repairing damage on the surface of a galvanized steel sheet according to claim 1, wherein the method is a metal ion selected from the group consisting of platinum, gold and mixtures thereof. 4. The method for repairing damage on the surface of a galvanized steel sheet according to claim 1, wherein the water-soluble metal salt is ferric chloride. 5. The method for repairing damage on the surface of a galvanized steel sheet according to claim 4, wherein the etching solution contains a small amount of phosphoric acid.