RU2487966C1 - Method of applying silver coating on titanium alloys - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves defatting, washing in hot flowing water, washing in cold flowing water, activating, washing in cold flowing water, washing in two collectors, washing in cold flowing water and drying. Activation is carried out in a solution of the following composition, g/l: sodium hypophosphite 8-12, hydrofluoric acid 2-6, distilled water - up to 1 l, pH 2.7, at temperature of +10 - +20°C for 10 minutes, and after activating and washing in cold flowing water, the silver precoating and basic coating are applied in a solution of the following composition, g/l: silver nitrate 15-25, potassium ferrocyanide 25-30, anhydrous sodium carbonate 10-15, water - up to 1 l. The silver precoating is applied at temperature of +18 - +25°C for 10 minutes with current density of 0.025 A/dm², and the basic silver coating is applied at temperature of +18 - +25°C with current density of 0.1 A/dm².

EFFECT: shorter process cycle.

3 ex

Description

The invention relates to methods for applying a silver coating to titanium alloys and can be used in the radio industry, instrumentation and the aircraft industry.

In modern technology, the technology of applying a silver coating to titanium alloys is known, consisting of the following sequence of operations [Electroplating. Handbook Ed. Ginberg A.M. et al. M .: Metallurgy, 1987, 736 pp.]:

- degreasing;

- flushing in hot running water;

- flushing in cold running water;

- etching;

- flushing in cold running water;

- lightening;

- flushing in cold running water;

- activation by applying a hydride layer by simply dipping concentrated sulfuric or hydrochloric acids into a solution;

- flushing in cold running water;

- applying a nickel coating;

- washing in the trap;

- flushing in cold running water;

- heat treatment;

- degreasing;

- flushing in hot running water;

- flushing in cold running water;

- activation;

- flushing in cold running water;

- copper coating;

- washing in the trap;

- flushing in cold running water;

- silver coating;

- washing in the trap;

- re-washing in the trap;

- flushing in cold running water;

- drying.

The closest in technical essence to the proposed method of applying a silver coating on titanium alloys is [Application 6436788 Japan, MKI ⁴ C25D 5/28, C25D 5/15 / Naito Tomijiro, Kawanobe Hirohira, Ando Naotake, Sato Dzunji, Matida Koji, Murooka Isamu; Shichizun Tokei K.K. - No. 62-190815; Claim 07/30/87; Publ. 02/07/89 // Kokai Tokoke Koho. Ser. 3 (4). - 1989-11. - p. 477-479. Titanium surface preparation]:

- degreasing;

- flushing in hot running water;

- rinse in cold running water

- etching;

- flushing in cold running water;

- lightening;

- flushing in cold running water;

- activation by applying the hydride layer by simply dipping into a solution containing 0.2-0.4% ammonium hydride fluoride and 15% water-soluble reducing agent sodium hydroxide;

- flushing in cold running water;

- applying a nickel coating;

- washing in the trap;

- flushing in cold running water;

- heat treatment;

- applying a gold or palladium coating;

- washing the trap;

- re-washing the trap;

- drying.

A disadvantage of the known methods is the deposition of a silver coating through a sublayer of Nickel or copper coating and a long technological cycle of its application.

The technical result of the invention is to obtain a silver coating on parts made of titanium alloys while reducing the technological cycle.

The essence of the invention lies in the fact that the method of applying a silver coating to parts made of titanium alloys is based on degreasing, washing in hot running water, washing in cold running water, activating, washing in cold running water, washing in two traps, washing in cold running water and drying.

New features of the claimed invention is that the activation is carried out in a solution of the composition g / l:

Sodium hypophosphite (GOST 200-76) 8-12 g / l Hydrofluoric acid (GOST 2567-89) 2-6 g / l Distilled water Up to 1 liter pH 2.7

at a temperature of + 10- + 20 ° C for 10 min, after activation and washing in cold running water, preliminary and main silver coating is applied in a solution of the composition

Silver nitrate (GOST 1277-75) 15-25 Potassium ferruginous (GOST 4207-75) 25 ÷ 30 Sodium carbonate (anhydrous) (GOST 83-79) 10 ÷ 15 Distilled water Up to 1 l

moreover, the preliminary silver coating is applied at a temperature of + 18- + 25 ° C for 10 min at a current density of 0.025 a / dm ² , and the main silver coating is applied at a temperature of + 18- + 25 ° C at a current density of 0.1 A / DM ² to obtain the required coating thickness. The silver coating deposition rate is 6 μm / h.

Example 1

The silver coating was applied to parts made of titanium alloy VT 1-0 as follows:

1. Surface preparation:

- Degreasing, for example, in a solution of the composition:

Na ₃ PO ₄ - 20 g / l, Na ₂ CO ₃ - 20 g / l, OP-10 - 2 g / l.

- Flushing in hot running water.

- Flushing in cold running water.

- Activation was carried out in a solution of the composition:

Sodium hypophosphite 10 g / l Hydrofluoric Acid 4 g / l Distilled water Up to 1 l pH 2.7 at a temperature of 18 ° C for 10 minutes

- Flushing in cold running water;

2. The preliminary silver coating on the parts of titanium alloys was carried out in a solution of the composition:

Silver nitrate fifteen Potassium ferruginous 25 Sodium carbonate (anhydrous) 10 The current density, A / DM ² 0,025 Temperature ° C eighteen Time min 10

3. The main silver coating was applied in a solution of composition according to claim 2 at a current density of 0.1 A / dm ²

Temperature ° C eighteen Time min thirty

4. Flushing in a trap.

5. Flushing in a trap.

6. Rinsing in cold running water.

7. Drying, for example with compressed air.

The details received a smooth, solid silver coating 3 microns thick. It was 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) and sea fog for 3 days.

Example 2

The silver coating was applied to parts made of titanium alloy VT 1-0 as follows:

1. Surface preparation as in example 1.

2. The preliminary and main silver coatings were applied in a solution of the composition:

Silver nitrate 19 Potassium ferruginous 28 Sodium carbonate (anhydrous) 12

For pre-silvering:

The current density, A / DM ² 0,025 Time min 10

For basic silver plating:

The current density, A / DM ² 0.1 Time min 60

3. Flushing in a trap.

4. Re-flushing in the trap

5. Rinsing in cold running water.

6. Drying, for example with air.

The parts received a smooth, solid silver coating on parts made of titanium alloys with a thickness of 6 microns. It was tested for cyclic effects of temperatures from -60 ° C to 85 ° C (3 cycles), exposure to tropical humidity for 12 days (relative humidity 98 ± 2% at 40 ° C) and sea fog for 3 days.

Example 3

The silver coating was applied to parts made of titanium alloy VT1-0 as follows:

1. Surface preparation as in example 1.

2. The preliminary and main silver coatings were applied in a solution of the composition:

Silver nitrate 22 Potassium ferruginous thirty Sodium carbonate (anhydrous) fifteen

For pre-silvering:

The current density, A / DM ² 0,025 Time min 10

For basic silver plating:

Current density, A / dm 0.1 Time min 90

The parts received a smooth, solid silver coating on parts made of titanium alloys with a thickness of 9 μm. It was tested for cyclic effects of temperatures from -60 ° C to 85 ° C (3 cycles), exposure to tropical humidity for 12 days (relative humidity 98 ± 2% at 40 ° C) and sea fog for 3 days.

Claims (1)

A method of applying a silver coating to parts made of titanium alloys, including degreasing, washing in hot running water, washing in cold running water, activating, washing in cold running water, washing in two traps, washing in cold running water and drying, characterized in that activation is carried out in a solution of the composition, g / l:
sodium hypophosphite 8-12 hydrofluoric acid 2-6 distilled water up to 1 l pH 2.7
at a temperature of + 10- + 20 ° С for 10 min, and after activation and washing in cold running water, preliminary and main silver coating is applied in a solution of the composition, g / l:
silver nitrate 15-25 potassium ferruginous 25-30 anhydrous sodium carbonate 10-15 water up to 1 l
moreover, the preliminary silver coating is applied at a temperature of + 18- + 25 ° C for 10 min at a current density of 0.025 A / dm ² , and the main silver coating is applied at a temperature of + 18- + 25 ° C at a current density of 0.1 A / DM ² to obtain the required coating thickness.