JPS59205481A - Metal anticorrosion - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention The present invention involves forming a phosphate film on the surface of metal, particularly iron and steel, and then impregnating the film with a cationic organic synthetic resin. This invention relates to a method for preventing corrosion of surfaces.

It is known to apply protective coatings to metal surfaces to improve corrosion resistance. For this purpose, a method is commonly used in which a solution forming a phosphate film is brought into contact with the metal surface.

Formation of a phosphate film is generally performed according to a procedure of cleaning, washing with water, forming a phosphate film, and washing with water. In order to further improve the corrosion resistance of the phosphate coating thus obtained, it is customary to carry out a finishing treatment subsequent to the formation of the phosphate coating.

Post-treatment methods for phosphate coatings include, for example, polyisocyanate 1-
Post-treatment methods are known in which the formation of a hydrophobic discontinuous film is avoided using an organic compound based on a modified resinous condensation product or the like, or by coating with a drying oil or a low-viscosity lacquer. [West German Application Publication No. 114'7820 and ``Method for post-treatment of iron parts treated with phosphate coating'' and ``Metal Products Industry and Electroplating Technology JMSV No. 6 (194
3) Section 229].

However, these treatments have not become widespread due to the lower quality of the films formed compared to chromate treatments.

In addition, chemical conversion coatings, especially phosphate coatings, formed on metal surfaces can be treated using the following general formula, where n is a positive number from 5 to 100, x is a hydrogen atom and/or CRR+0f-1 group, and R and [<1 is a hydrogen atom or an aliphatic and/or aromatic group having 1 to 12 carbon atoms (West German Patent Application No. 3146265).

It is also known that post-treatment is carried out using a solution containing a poly-4-vinylfuranol compound represented by This method has the disadvantage that, in some cases, partial dissolution of the conversion coating occurs during surface post-treatment.

Finally, it is also known to first after-treat the phosphate coating with a Cr(Vl)-containing solution and then finish it with inorganic compounds, oils, waxes or lacquers [W, Raus
ch '''Metal phosphate film chemical conversion treatment pa Euoen
G., Leuse edition (1974), paragraph 120]
However, according to this finishing treatment, after galvanizing, a corrosion-proofing effect close to that of the surface treated with chrome-1 can be achieved. However, no further effect can be expected. Another disadvantage is that this type of impregnated coating is liquid or a soft to semi-hard coating with low wear resistance.

The object of the present invention is to provide a method for forming a corrosion-resistant and abrasion-resistant skin on the surface of metal, especially ridges and steel, without the disadvantages of the previously mentioned known methods. It is to provide the following.

The task is to first apply at least 8g/-1T1 to the metal surface.
This is achieved by forming a phosphate film of No. 2, followed by applying at least 8(]/m2 of the synthetic resin electrolessly using an aqueous solution or dispersion of a cationic synthetic resin, and then baking.

In this way, the synthetic resin film coated on the phosphoric acid JN film produces an extremely excellent corrosion resistance effect due to the additive effect with the underlying phosphate film. This is in stark contrast to the prevailing idea that the coating layer must be thin (e.g. W, Rausc.
h “Metal phosphate film chemical conversion treatment” Eugen
(see G., Leuse edition 1974, paragraph 142).

Improved fish benefiting from the method according to the invention is up to 40 sp/1T.
It is possible to coat cationic synthetic resins up to i2. Even if it is made thicker than this, the anti-corrosion effect will not be added to the actual Y1 level.

In order to form a phosphate film layer, zinc, zinc and iron, manganese, manganese and zinc,
Phosphate film conversion treatment containing manganese and iron, manganese, zinc and iron, zinc and calcium or zinc, calcium and iron 1! I! The solution is applied to form a phosphate film by known methods.

In order to modify the phosphate film, in addition to the above-mentioned film-forming cations, for example, Ni, Qu,
A cation selected from ions such as M(], alkali metals, ammonium, etc. is added. In the phosphorus M salt film conversion treatment method, which requires a relatively long time to form a film,
Although the phosphate radical in the phosphatizing solution is the only anion in the acidic aqueous phosphate solution, other anions such as nitrate ions are often added to the conversion bath to promote film formation or to adjust the acidity. , nitrite ion, chloride ion,
Anions selected from sulfate ions, chlorate ions, fluoride ions, fluoride ions, citrate ions, and the like are added.

Phosphate coating conversion baths in which a significant proportion of divalent iron is present in the solution are particularly suitable for the process according to the invention.

The concentration of the phosphate film conversion treatment bath is preferably selected from a range of 20 to 120 points in terms of total acidity, and the concentration of the phosphate film conversion treatment bath is preferably selected from a range of 20 to 120 points in terms of total acidity. r
! Temperatures usually range from 40 to 98°C. To be elected. or,
A dipping method is preferred for film formation. This is because the required coating weight in the present invention is secured by a simple dipping method. The immersion treatment time is usually 4 to 30 minutes.

In the method of the invention, the synthetic resin liquid used for impregnation is partially or completely neutralized with an organic acid or phosphoric acid and is present as an emulsion, dispersion and/or colloidal solution in an aqueous medium, and a solid The content is preferably 5 to 25% by weight.

Cationic synthetic resins are selected from polycondensation and polycondensation resins, and their cationic function is obtained, for example, by imparting basic nitrogen-containing groups which form cations after addition of acid in an aqueous medium. Cationic acrylic acid resins are obtained by polymerizing ICs such as N1N-dimethylaminoethyl methacrylate-1. Cationic resins can also be made by reacting the Mannich base of bisphenol A with an epoxy resin. In the process according to the invention, modified epoxy resins are particularly suitable for the addition of amines, which are made soluble in phosphoric acid and which, by addition of diisocyanates, can be crosslinked during baking.

Also suitable are lacquer and enamel formulations such as colorants, fillers and anti-staining pigments, soluble corrosion inhibitors, organic solvents and/or additives for improving the physical properties of the film and for accelerating the crosslinking reaction during baking. Aqueous or dispersed cationic synthetic resin solutions which additionally contain additives and modifiers known from Coated paints are also suitable.

Within the framework of the present invention, excellent results with extremely high fl-ability can be obtained by electrolessly coating a phosphorus I salt film with an aqueous solution containing these cationic synthetic resins. The organic film J5 of the present invention is formed by applying an aqueous solution or dispersion containing a cationic synthetic resin to the surface that has been subjected to the chemical conversion treatment for the phosphate film. This application is carried out by spraying, pouring, or dipping, or in some cases following any of these methods of application, by shaking off any excess resin solution. .

In order to avoid leaving defects in the organic film after one application, or when a large coating weight is intended,
After applying the cationic synthetic resin liquid, it is desirable to repeat a short period of intermediate drying at least twice, and finally to perform baking.

Intermediate drying should be carried out until the organic film reaches sufficient mechanical strength.

The seizure of cationic synthetic resin film is usually 160 to 2
It is carried out for 5 to 30 minutes at a temperature of 00°C.

Furthermore, as a further advantageous means in implementing the present invention,
1711 cationic synthetic resin to improve corrosion resistance
The phosphate coating is then post-treated with a known Cr(Vl)-containing aqueous passivation solution. The source of Cr (Vl) in this passivation solution is chromic anhydride,
Substrates such as chromate or alkali dichromate are used.

Another advantageous feature of the present invention is to post-treat the cationic synthetic resin film with an anti-corrosive oil following baking.
This is one aspect. Corrosion resistance is often further improved by this. Also, when treated with a vibrator, a pleasant and uniformly shiny film is formed.

The method according to the invention is particularly suitable for imparting a high degree of corrosion protection to entry-level production parts used in the field. Type 11 objects to be processed include uA parts such as screws, nuts, washers, springs, fasteners, and brake parts. . The corrosion resistance of the coating formed by the method of the present invention clearly exceeds that of chromate-treated coatings, electrically zinc- and cadmium-plated coatings, etc.

As a typical J culm for carrying out the present invention, the following work procedure can be mentioned, for example.

i, n+> Grease: Application of strong alkaline deodorant (soaking or spraying) or organic solvent 2, water washing 3, removal of leakage scale: pickling with hydrochloric acid, sulfuric acid or phosphoric acid, depending on the case Application of lean blast method or grinding means 4, Water washing 5, Water washing before chemical formation: Warm water, addition of surfactant in some cases 6, Phosphate film chemical conversion treatment 8, Post-passivation treatment Nichrome (Vl) - U 9. Drying (if desired) 10. Impregnating the phosphate film with a cationic synthetic resin solution Modification by adding pigments) /emulsion,
Solid content: 25%, immersed at 25°C for 1 minute, then dried in air, immersed once for 1 minute 11, Curing of resin film: Bake at 185°C for 20 minutes Degreasing listed in item 1 or item 3] Descaling and scale removal is omitted if the parts to be treated are free of grease or grease or scale.

Steel parts processed according to the above procedure are SSD I
According to the N50021 salt spray test method, rust was observed for the first time after 800 to 1000 hours. Instead of impregnating with a cationic resin, the above phosphate film is coated with anti-seize oil 2T or anti-seize wax.The occurrence of rust depends on the type of anti-seize agent used.
Ij could be observed indirectly.

(1 idiot)

Claims (6)

[Claims] (1) In a method in which a phosphate film is formed on the surface of a metal, especially iron and steel, and then the film is impregnated with an organic synthetic resin, the surface of the metal is first coated with at least 8 (1/Tl1
A metal characterized by forming a phosphate film according to No. 2, and then electrolessly applying at least 8 g/nF of a synthetic resin using an aqueous solution or dispersion of a cationic synthetic resin, and then baking. Corrosion prevention method. (2) The method according to claim 1, characterized in that a synthetic resin of up to 40 (J/cm2) is applied and then baked. (3) From lacquer formulations and enamel formulations such as coloring agents, filler pigments and/or anticorrosion pigments, soluble corrosion inhibitors, organic solvents and/or additives for improving film physical properties, and additives for accelerating crosslinking reactions during baking. Claim 1 or 2, characterized in that the resin is applied with an aqueous solution or dispersion of a cationic synthetic resin which additionally contains known additives and modifying agents. the method of. (4) Claims 1 to 3 characterized in that the cationic synthetic resin is coated by at least two applications with short-term intermediate drying and subsequent baking.
The method described in any one of the paragraphs. (5) Any one of claims 1 to 4, characterized in that the phosphate film is treated with an aqueous passivating agent containing Or (Vl) before applying the cationic synthetic resin. The method described in one. (6) The method according to any one of claims 1 to 5, characterized in that, subsequent to the baking of the cationic synthetic resin film, finishing treatment is performed with an anti-sweetening oil.