RU2320773C1 - Method for deposition of conversion coating onto parts made from aluminum and alloys thereof - Google Patents

Abstract

FIELD: process for coating of parts made from aluminum of alloys thereof.

SUBSTANCE: method involves preparing part surface for coating process; dipping part into solution of composition including, g/l: orthophophoric acid 40-50, chromic anhydride 5-7, hydrofluoric sodium 3-4, at temperature of 20-30 C; holding in solution during 4-7 min; washing with cold running water and drying. Parts dipped into solution are subjected to harmonic vibrations with fixed frequency ranging between 300 Hz and 600 Hz and mean-square acceleration of 9-11 m/s.

EFFECT: provision for producing of thick corrosion-resistant coating on parts made from aluminum and alloys thereof.

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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

at a temperature of 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

at a temperature of 20-30 ° C, processing time 3-12 minutes;

- flushing in cold running water;

- drying.

The disadvantage of this method is the small coating thickness (0.5-1.0) microns and its low corrosion resistance.

The technical task of the invention is to obtain thick corrosion-resistant 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 parts of aluminum and its alloys immersed in a solution are affected by harmonic oscillations with a fixed frequency in the range of 300-600 Hz and rms accelerations of 9-11 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 temperature, ° С 20-30

and exposure to harmonic oscillations with a fixed frequency in the range of 300-600 Hz and a mean square acceleration of 9 m / s ² .

processing time, min 5

3. Rinsing in cold running water.

4. Drying, for example, with compressed air.

On the details received a coating thickness of 3.0 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 temperature, ° С 20-30

and exposure to harmonic oscillations with a fixed frequency in the range of 300-600 Hz and a mean square acceleration of 10 m / s ² .

processing time, min 6

3. Rinsing in cold running water.

4. Drying, for example, with compressed air.

The resulting coatings were tested as in example 1. No corrosion spots were found on the surface of the parts.

Example 3

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 temperature, ° С 20-30

and exposure to harmonic oscillations with a fixed frequency in the range of 300-600 Hz and a mean square acceleration of 11 m / s ² .

processing time, min 7

3. Rinsing in cold running water.

4. Drying, for example, with compressed air.

The resulting coatings were tested as in example 1. No corrosion spots were found on the surface of the parts.

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, washing in cold running water and drying, characterized in that the parts immersed in the solution are affected by harmonic oscillations with a fixed frequency in the range of 300-600 Hz and RMS acceleration 9-11 m / s ² .