SU732412A1 - Method of platinum-plating of metals - Google Patents

Description

I

The invention relates to electroplating, in particular to electrolytic deposition of platinum on titanium with a chain of use of platinized titanium as corrosion-resistant electrodes for electrochemical production, as well as insoluble anodes in the electrochemical protection of ships and marine structures.

The use of symmetric alternating current of industrial frequency for electrodeposition of metals with valve action is known. F. The structure and quality of the resulting coatings are rarely satisfactory. Changing the electrolysis conditions in the direction of improving the quality of the coatings changes the degree of current output, as a result of which the deposition of the metal can practically cease.

Closer to the invention is a method of platinization of metals, for example copper or nickel, in an electrolyte containing platinum diaminodinitrite, ammonium nitrate, sodium nitrate and ammonium hydroxide 2. The known method is carried out using direct current or reversing the current at a density of 0.5-5 A / dm and a temperature of 99-98s.

However, the known method does not allow nonj-BTb coatings of sufficiently high quality (see table p. 6).

to

In addition, the use of direct current requires the use of AC rectifiers, which complicates the instrumentation and does not allow the application of a layer of platinum

15 immediately on two electrodes, which reduces the productivity of the process.

The proposed method is different from that in order to reduce

20 porosity of coatings, increasing their OTpligability and adhesion to the substrate during the platinization of titanium, the process is conducted with alternating current ind3

Lennaya frequency density of 5-12 A / dm N temperature

Pfeed coating the surface of the titanium electrodes is prepared as follows.

Mechanical cleaning and polishing.

Washing with water

The electrolytic degreasing by alternating current of industrial frequency (50 Hz) in a solution containing 20 g / l sodium hydroxide, 25 g / l sodium carbonate and 25 g / l sodium phosphate at a tempering rate of 70 C and a current density of 5 A / dm for 4- 5 minutes.

Rinsing with water.

AC alternating current in a solution containing 800 g / l of sulfuric acid and 30 g / l of 6trxpOMaTa potassium at a temperature of 25 ° C and a current density of 5 for 5 minutes "

Rinsing with water.

Electrolytic deposition of titanium on titanium is carried out in a 20 cm electrolytic cell, a titanium tube with a diameter of 14 ivfM (electrode) containing a titanium rod with a diameter of 6 mm (second electrode). The core is carefully centered. Electrode length 2OO mm. The platinization electrolyte contains, g / l:

Platinum diamino dinitrite

(in terms of metal) 15

Ammonium nitrate1OO

Sodium Nitrite 1 O

Ammonia (25% water

solution) to, 5

The electrolyte circulates continuously in a closed loop with speed

Electrolysis mode and results

2412A

24 ml / h The electrolyte is stable in operation until complete precipitation of platinum and electrolyte platinum.

Within the temperature range of 10–80 ° C and a current density of 5–12 A / dm, the deposition of platinum on titanium proceeds with approximately the same total yield of platinum with a current of 8%.

According to the proposed method, thick (up to 150 lkm) thick and shiny coatings are obtained. When examined under a microscope, no pores were found, the coating structure is fine crystalline without foreign implants. The adhesion of platinum with titanium is good — under a microscope, the formation of an intermediate mixed layer of adhesion with a thickness of 20 µm is seen (after mechanical polishing, this layer appears as a composite; it forms part of a platinum coating).

Adjustment of the initial electrolyte in precipitation is not necessary, since the concentration of platinum in the electrolyte does not affect the total metal yield for current 2B and the quality of the precipitate.

Both electrodes are coated with platinum, and the thickness of the platinum layer is less with an electrode with a larger surface.

The invention can be illustrated by several examples of Ig presented in the table.

As can be seen from the table, the use of alternating current of industrial frequency.:: Allows to significantly improve the quality of the coating, as well as simplify the instrumentation and improve the performance of the process by coating two electrodes at once.

Examples

pH

Temperature, ° С

2 Current density, A / dm

Duration, min Tolshch1gaa, microns

Continuing taip.

Claims (1)

The claims of 5-12 A / dm 2 and a temperature of 70 when platinizing titanium, the process is conducted by an alternating current of industrial frequency