RU2562196C1 - Method of producing of conducting coating on products from magnesian alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes degreasing of products in gasoline, drying in air at the room temperature, alkaline processing in the solution containing 400-450 g/l of sodium hydroxide at the temperature 100-120°C, washing with warm and cold flowing water, processing in the solution containing 100-150 g/l of chromic anhydride at the temperature 15-30°C, washing in the trapping bathtub with the distilled cold water, washing with flowing cold water and application of chemical oxide coating in the solution containing, g/l: chrome anhydride - 4.0-8.0, fluoric sour ammonium - 1.5-2.0, ferricyanic potassium - 0.5-1.0, at the temperature 15-30°C within 10-20 minutes. Thickness of the coating layer is 0.5-5.0 mcm.

EFFECT: making a conducting coating stable to corrosion and with uniform thickness along the whole surface of the processed product.

2 tbl, 1 ex

Description

The invention relates to chemical surface treatment of products from a magnesium alloy and can be used in the space, aviation, automotive, electronic industries.

A known method of obtaining a protective coating for products from magnesium alloys as protection against corrosion in the process of preparing the surface for paint coatings, including the removal of oxides from the surface of the product, degreasing it with an alkaline solution, processing in a solution of chromic anhydride and applying an oxide film to the parts chemically from solution, containing, g / l:

potassium dichromate 70-100 magnesium sulfate 40-70 ammonium sulfate 40-60

A paint or powder coating can be applied to the resulting film (OST 3-4123-78 “Metallic and non-metallic inorganic coatings. Typical technological processes for producing coatings”).

Known oxide film refers to corrosion protection and is not electrically conductive.

A known method of producing an electrically conductive film on magnesium alloys by processing a non-conductive protective film in a solution of "Efren-K" brand N-2. Efren-K grade N-2 is a solution based on fluorine-containing surfactants with the addition of corrosion inhibitors in a mixed solvent.

The method was carried out as follows:

- degreasing of parts in gasoline, followed by drying in air;

- alkaline treatment in a solution of caustic soda (400-450 g / l);

- washing in warm and then in cold running water;

- processing in a solution of chromic anhydride (100-150 g / l);

- rinsing in a capture bath with distilled cold water;

- washing with running cold water;

- chemical oxide coating;

- applying a second oxide coating chemically in a solution of "Efren-K" brand N-2.

As a result of the deposition of an oxide coating in an Efren-K solution of grade N-2 on products from a magnesium alloy, an electrically conductive film up to 0.1 μm thick was obtained, colorless, practically invisible (Corrosion protection of chemically oxidized parts from magnesium and aluminum alloys. http://lakokraska-ya.ru/info/detail.php?ID=1244). This film is applied to increase the protective properties of the previously deposited film and provide contact electrical conductivity.

The disadvantage of this method is the small thickness of the coating. In addition, this coating is applied to a previously applied chemical oxide coating, which complicates the process and makes it more expensive.

The objective of the invention is to simplify the method of obtaining a conductive coating.

The technical result that provides a solution to the problem is achieved by the fact that in the proposed method for producing a conductive coating on magnesium alloy products, including degreasing of magnesium alloy products in gasoline, drying in air at room temperature, alkaline treatment in caustic soda solution (400-450 g / l), at a temperature of 100-120 ° C, rinsing with warm and cold running water, treatment in a solution of chromic anhydride (100-150 g / l) at a temperature of 15-30 ° C, rinsing in a capture bath with distilled cold water Second, wash with cold water, application of oxide coatings by chemical means, is used as a coating oxide fluoride film, which coating is carried out in a solution containing in g / l:

chromic anhydride 4.0-8.0 ammonium fluoride acid 1.5-2.0 potassium iron-ferrous 0.5-1.0

at a temperature of 15-30 ° C for 10-20 minutes.

The technical result of the proposed method is to obtain a conductive coating resistant to corrosion, having a uniform coating thickness over the entire surface of the workpiece. The thickness of the resulting coating is 0.5-5.0 microns.

Examples of implementation.

For research, samples were taken from MA15 magnesium alloy 10 × 10 cm in size. The samples were degreased in gasoline for 1 minute at room temperature, then dried in air at room temperature for 10 minutes.

Alkaline treatment was carried out in a solution of caustic soda (400-450 g / l), at a temperature of 100-120 ° C for 5-20 minutes.

Washed with warm running water at a temperature of 45-55 ° C for 0.5-1 minutes.

Washed with cold running water at a temperature of 18-30 ° C for 0.5-1 minutes.

Processed in a solution of chromic anhydride (100-150 g / l) at a temperature of 15-30 ° C for 10-15 seconds.

Washed in a capture bath with distilled cold water at a temperature of 15-30 ° C for 0.5-1.0 minutes.

Washed with running cold water at a temperature of 15-30 ° C for 0.5-1.0 minutes.

The oxide coating was applied in a solution containing, g / l:

chromic anhydride 4.0-8.0 ammonium fluoride acid 1.5-2.0 potassium iron-ferrous 0.5-1.0

at a temperature of 15-30 ° C for 10-20 minutes.

Washed with cold non-running water at a temperature of 15-30 ° C for 0.5-1.0 minutes

Washed with cold running water at a temperature of 15-30 ° C for 0.5-1.0 minutes.

Blowed with compressed air.

Dried in air at a temperature of 15-25 ° C.

Conducted visual control of the appearance of the parts.

The thickness of the resulting coating was measured.

Measured the transition resistance of the coating.

Further, the samples were put to corrosion tests according to OST V3-9.015-84:

- resistance to high humidity (95%) at a temperature of 35 ° C for 5 days;

- resistance to the effects of low ambient temperature at a temperature of minus 40 ° C for 3 hours;

- conducted visual inspection of the appearance of the parts;

- checked the transient resistance of the parts.

The research results are presented in tables 1 and 2.

The thickness of the resulting coatings was 0.5-5.0 μm. All samples withstood climatic tests; no corrosion damage to the protective coating was found on the samples. The resulting oxide coating is electrically conductive, wear-resistant, and not subject to corrosion.

Claims (1)

A method of obtaining a conductive coating on magnesium alloy products, including degreasing of products in gasoline, drying in air at room temperature, alkaline treatment in a solution containing 400-450 g / l sodium hydroxide, at a temperature of 100-120 ° C, processing in solution, containing 100-150 g / l of chromic anhydride, washing in a capture bath with distilled cold water, applying a chemical oxide coating, with intermediate washing in cold and warm water, characterized in that the chemical oxide coating is carried out t in a solution containing, g / l:
chromic anhydride 4.0-8.0 ammonium fluoride acid 1.5-2.0 potassium iron-ferrous 0.5-1.0
at a temperature of 15-30 ° C for 10-20 minutes.