RU2354756C1 - Method of galvanic nickel coating application - Google Patents

Abstract

FIELD: electrics.

SUBSTANCE: method involves nickel sedimentation from electrolyte including nickel sulfate 0.322-0.889 mol/l, lactic acid (80%) 20-30 ml/l, and water, at pH of 3.0-4.0, electrolyte temperature of 20-25°C, cathode current density of 1.0-3.0 A/dm², applying graphite anode. Electrolyte does not include toxic organic additives.

EFFECT: gleaming nickel coatings clinging fast to substrate, at high current efficiency.

5 tbl, 1 dwg

Description

The invention relates to a galvanic method for producing nickel coatings.

Known electrolyte of the following composition:

1. NiSO ₄ · 7H ₂ O - 250-300 g / l, NaCl - 10-15 g / l, N ₃ BO ₃ - 25-40 g / l, KF or NaF - 5-6 g / l, disodium salt naphthalene-1,5-disulfonic acid - 1.5-2.0 g / l, 1,4-butynediol - 0.2-0.5 ml / l, pH 4.5-5.5, temperature 20-50 ° C, the cathodic current density is 0.8-3.5 A / dm ² [1].

This nickel plating electrolyte has a number of drawbacks, among which it is possible to single out a small scattering power, and sufficiently large internal stresses arising in the coating during the deposition process. The disadvantages include the content in the electrolyte, in addition to nickel cations, toxic anions and organic substances, which significantly increase the complexity of the disposal of spent electrolyte and wastewater treatment from the nickel plating site.

Of the currently used electrolytes, the closest in composition and technological characteristics is an electrolyte containing: 230-320 g / l of nickel (II) sulfate crystalline hydrate, 40-60 g / l of nickel (II) chloride crystalline hydrate, 30-40 g / l boric acid, with the addition of 1,4-butynediol, saccharin and phthalimide, pH 5.0. Operating temperature range 50-60 ° C. The working current density is 2-7 A / dm ² [1].

A sufficiently high operating temperature (from 50 to 60 ° C) creates additional difficulties in operation due to the evaporation of the solution, and the presence of organic additives complicates the disposal of spent electrolyte and wastewater treatment.

The technical result of the proposed method is to obtain brilliant, well adhered to the base coatings of Nickel with high current efficiency. The electrolyte should be easy to prepare and adjust, and not contain toxic organic additives. The working temperature of the electrolyte should not be higher than 30 ° C.

This is achieved by the fact that in the method of applying a plating of nickel from an electrolyte containing nickel sulfate and water, at a cathodic current density of 1.0-3.0 A / dm ² , according to the invention, nickel sulfate is dissolved in water - 0.322-0.889 mol / l, lactic acid (80%) - 20-30 ml / l, pH - 3.0-4.0, after which the process of electrolytic deposition of Nickel at a temperature of 20-25 ° C using a graphite anode.

As a complexing agent, lactic acid was selected. It is used as a dietary supplement, widely distributed in nature, is an intermediate of metabolic processes in biological tissues, is easily biodegradable and therefore environmentally friendly.

Not identified solutions that have signs of the proposed method.

The method of applying plating nickel is as follows.

Nickel sulfate is dissolved in distilled water according to the composition of the electrolyte. Then add lactic acid, bring to volume with distilled water and mix. Precipitation is carried out at a cathodic current density of 1-3 A / dm ² , at a temperature of 20-25 ° C using a graphite anode.

Based on the studies performed, for the deposition of shiny coatings with nickel, an electrolyte of the following composition can be recommended:

- Nickel sulfate - 0.322-0.889 mol / L, lactic acid (80%) - 20-30 ml / L, pH 3-4. At a cathodic current density of 1 to 3 A / dm and a temperature of 20-25 ° C, the cathodic current output is 60-85%. Glossy coatings are deposited from this electrolyte without the addition of brightening agents.

When preparing the solution, it must be taken into account that a higher content of nickel ions in the electrolyte should correspond to a higher content of lactic acid, a lower pH value. With an increase in the concentration of the solution components, the process can be conducted at a higher current density. The following are approximate compositions of such solutions and electrolysis modes:

1. Nickel sulfate - 0.712-0.889 mol / l, lactic acid (80%) - 30 ml / l, pH - 3-3.5. At a cathodic current density of 1 to 3 A / dm ² and a temperature of 20-30 ° C, the cathodic current output is 60-80%. The appearance of the resulting coatings is shown in the drawing.

2. Nickel sulfate - 0.322-0.373 mol / L, lactic acid (80%) - 20 ml / L, pH 4.0. At a cathodic current density of 2 A / dm ² and a temperature of 20-30 ° C, the cathodic current output is 80-85%. The appearance of the resulting coatings is shown in the drawing.

The advantages of industrial use of the claimed electrolyte:

1. The complex of Nickel with lactic acid can be easily destroyed at the stage of wastewater treatment by shifting the pH value above 5.

2. The electrolyte is relatively simple in composition, does not contain toxic organic additives, it allows to obtain coatings of good quality with high cathode current output.

3. The operating temperature range in this electrolyte is reduced to 20-25 ° C, which significantly reduces the evaporation of the electrolyte, and there is no need to take additional measures to reduce evaporation from the surface of the electrolyte.

Table 1 Dependence of the cathodic current efficiency of nickel on the cathodic current density. i _k , A / dm ₂ one 2 3 5 twenty BT,% 60 77 fifty 8.7 5

table 2 The dependence of the cathode current efficiency of Nickel on the concentration of Nickel ions at a current density of 2 A / DM ² . [Ni ²⁺ ], mol / L 0.186 0.254 0.322 0.356 0.372 0.534 0.712 0.889 1,068 BT,% 26.7 24.4 30.1 33 34.9 40 55.5 77 54

Table 3 Dependence of the cathode current efficiency of nickel on the concentration of lactic acid. [Hlact], ml / l 10 twenty thirty 40 fifty BT,% 35 77,2 80 51 58

Table 4 The dependence of the cathode current efficiency of Nickel on pH at a cathodic current density of 2 A / DM ² . pH 2.0 2.5 3.0 3,5 4.0 BT,% 1,0 eleven 77 80 88

Table 5 Dependence of the cathode current efficiency of nickel on t ° C. t ° C 10 twenty thirty 40 fifty BT,% 37 80 55 48 33

Literature

1. Electroplating coatings in mechanical engineering. Directory. In 2 volumes. / Ed. M.A.Shluger. - M.: Mechanical Engineering, 1985. - T.1. 1985.240 s. with silt.

Claims (1)

A method for applying electroplated coatings with nickel, including the deposition of nickel from an electrolyte containing nickel sulfate and water, at a cathode current density of 1.0-3.0 A / dm ² , characterized in that the deposition is carried out from an electrolyte containing nickel sulfate 0.322-0.889 mol / l, lactic acid (80%) 20-30 ml / l and water, at pH 3.0-4.0, electrolyte temperature 20-25 ° C, using a graphite anode.