RU2333291C1 - Method of conversion coating application on parts made of aluminium and its alloys - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention may be used in radio engineering industry, instrument making, aircraft industry for preparation of pore-free thick coatings on parts made of aluminium and its alloys. Method includes preparation of their surface for coating, immersion into solution with the following composition, g/l: orthophosphoric acid 40-50, chrome anhydride 5-7, hydrofluoric sodium 3-4, at temperature of 20-30°C, soaking in solution for 4-7 min, flushing in clod running water and drying, at that parts that are immersed into solution are exposed to wideband accidental vibration in the range of 10-1000 Hz and mean-square acceleration of 18-22 m/sec².

EFFECT: development of method for application of conversion coating on parts made of aluminium.

3 ex

Description

The invention relates to a method for applying a conversion coating to parts of aluminum and its alloys and can be used in the radio industry, instrument making, and the aircraft industry.

In modern technology there is a known method of applying a conversion coating to parts of aluminum and its alloys, consisting of the following sequence of operations [Electroplating. Handbook Ed. Ginberg A.M. et al. M .: Metallurgy, 1987, 736 pp.]:

- preparation of the surface for coating;

- applying the conversion coating by immersion in a solution of the composition, g / l:

Phosphoric acid 50-60 Chromic anhydride 7-8 Hydrofluoric acid (40%) 4-5

temperature 15-30 ° C;

processing time 5-20 min;

- flushing in cold running water;

- drying.

The closest in technical essence to the proposed method for applying a conversion coating on parts of aluminum and its alloys is a method for applying a conversion coating [OST 107.460092.001-86 Metallic and non-metallic inorganic coatings. Typical technological processes]:

- preparation of the surface for coating;

- applying the conversion coating by immersion in a solution of the composition, g / l:

Phosphoric acid 40-50 Chromic anhydride 5-7 Hydrogen Fluoride 3-4

temperature 20-30 ° C;

processing time 3-12 min;

rinsing in cold running water;

drying.

The disadvantage of this method is the large porosity and small coating thickness (0.5-1.0) microns.

The technical task of the invention is to obtain non-porous thick coatings on parts made of aluminum and its alloys.

The solution to the problem is achieved by the fact that the method of applying a conversion coating to parts of aluminum and its alloys is based on preparing their surface for coating, immersion in a solution of the composition, g / l:

Phosphoric acid 40-50 Chromic anhydride 5-7 Hydrogen Fluoride 3-4

at a temperature of 20-30 ° C, holding in solution for 4-7 minutes, washing in cold running water and drying.

Distinctive features of the proposed method is that the parts of aluminum and its alloys, immersed in the solution, are affected by broadband random vibration in the range of 10-1000 Hz and rms acceleration of 18-22 m / s ² .

Example 1

The coating was carried out on parts made of aluminum alloy Amts as follows:

1. Surface preparation for coating;

2. The application of the conversion coating from a solution of the composition, g / l:

Phosphoric acid 40-50 Chromic anhydride 5-7 Hydrogen Fluoride 3-4

at a temperature of 20-30 ° C and exposed to broadband random vibration in the range 10-1000 Hz and rms acceleration of 18 m / s ² (treatment time 5 minutes).

3. Rinsing in cold running water.

4. Drying, for example, with compressed air.

The details received a non-porous coating with a thickness of 2.8 microns. They were tested for cyclic exposure to temperatures from -60 ° C to 85 ° C (3 cycles), exposure to tropical humidity for 12 days (relative humidity 98 ± 2% at 40 ° C).

Example 2

The coating was carried out on parts made of aluminum alloy D-16 as follows:

1. Surface preparation for coating;

2. The application of the conversion coating from a solution of the composition, g / l:

Phosphoric acid 40-50 Chromic anhydride 5-7 Hydrogen Fluoride 3-4

at a temperature of 20-30 ° C and exposure to broadband random vibration in the range of 10-1000 Hz and rms acceleration of 20 m / s ² (processing time 6 min).

3. Rinsing in cold running water.

4. Drying, for example, with compressed air.

The resulting coatings were tested as in example 1. Received a non-porous coating with a thickness of 3.5 μm. Corrosive foci on the surface of the parts were not found.

Example 3

The coating was carried out on parts made of Amg aluminum alloy as follows:

1. Surface preparation for coating;

2. The application of the conversion coating from a solution of the composition, g / l:

Phosphoric acid 40-50 Chromic anhydride 5-7 Hydrogen Fluoride 3-4

at a temperature of 20-30 ° C and exposure to broadband random vibration in the range of 10-1000 Hz and rms acceleration of 22 m / s ² (processing time 7 min).

3. Rinsing in cold running water.

4. Drying, for example, with compressed air.

The resulting coatings were tested as in example 1. Received a non-porous coating with a thickness of 3 μm. Corrosive foci on the surface of the parts were not found.

Claims (1)

The method of applying a conversion coating to parts of aluminum and its alloys, including preparing their surface for coating, immersion in a solution of the composition, g / l: phosphoric acid 40-50 chromic anhydride 5-7 hydrogen fluoride 3-4 at a temperature of 20-30 ° C, holding in solution for 4-7 minutes, rinsing in cold running water and drying, characterized in that the parts immersed in the solution are affected by broadband random vibration in the range of 10-1000 Hz and rms acceleration 18-22 m / s ² .