GB2033429A

GB2033429A - Electrolyte for Cathodic Deposition of Alloys of Nickel with Molybdenum

Info

Publication number: GB2033429A
Application number: GB7934779A
Authority: GB
Original assignee: Statni Vyzkumny Ustav Materialu
Current assignee: Statni Vyzkumny Ustav Materialu
Priority date: 1978-10-06
Filing date: 1979-10-08
Publication date: 1980-05-21
Also published as: DE2940462C2; CS201413B1; DE2940462A1; GB2033429B; DD148159A3

Abstract

An aqueous electroplating solution comprises nickel sulphosalicylate in a 0.1 to 1.05 M concentration, and a molybdenum salt in a 0.001 to 0.02 M concentration. The electrolyte may also include a 0.01 to 0.02 M concentration of nickel halide e.g. nickel dibromide, and a 0.002 to 0.04 concentration of a surfactant. The electrolyte results in low stress platings.

Description

SPECIFICATION Electrolyte for Cathodic Deposition of Alloys of Nickel with Molybdenum The invention concerns an electrolyte for cathodic deposition of alloys of nickel containing molybdenum. Such alloys of nickel with molybdenum produced in an electrolytic method are better than chemically pure nickel with regard to certain of their properties.

The prior literature teaches that the nickel coatings have great internal stresses so that the deposition of thick layers is not possible.

Moreover, the electroplating process has a very low cathodic current efficiency, especially in acidic solutions where it may only reach values of about 30%.

The known electrolytes use nickel sulphate as a basic component. Further, they contain complex-producing materials, such as citric acid or tartaric acid and ammonia. Molybdenum may be used in the form of sodium monomolybdate.

The present invention provides an aqueous electroplating solution which comprises nickel sulphosalicyiate in a 0.1 to 1.05 M concentration, and a molybdenum salt in a 0.001 to 0.02 M concentration.

Preferably, the molybdenum salt is disodium monomolybdate.

In order to adjust the solubilities, a nickel halide may also be included in a concentration of 0.01 to 0.2 M; nickel dibromide is preferred.

Moreover, an ionic or non-ionic surfactant may be also incorporated in a concentration of 0.002 to 0.04 M; disodium lausic sulphate is preferred.

Molybdenum may in general be in the form of a molybdate. It is not necessary, with regard to the complex-forming properties of the basic electrolyte, to add further complex-forming matter, such as organic hydroxy acids, which tend to deteriorate the properties of the coatings. The electrolyte results in a very low level of macrostress at a temperature above 400 C. The level of stress is further lowered with increasing temperature. The temperature is, in spite of the fact that the sulphosalicylate anion is also stable in aqueous solution at higher temperatures, limited however, by technologic problems, such as vaporization and corrosion. The cathodic current densities range between the limits from 1 to 10 A.dm-2 according to the conditions of the electrolysis.The cathodic current efficiency is higher than 90% with the pH values higher than 3.

Embodiments of the electrolyte solution according to the invention are by the way of illustration shown in the following Examples.

Example 1 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum contained nickel sulphosalicylate in a concentration of 0.8 M and disodium monomolybdate in a concentration of 0.01 M.

The cathodic current density was 3 A.dm-2, the temperature of the bath 500C and its pH was 4.

The deposited layer had a content of molybdenum of 7.5 percent by weight, its internal stress was 30 MPa and its microhardness 800 HM.

Example 2 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum with the use of a halide contained nickel sulphosalicylate in a concentration of 0.75 M, disodium monomolybdate in a concentration of 0.005 M and nickel dibromide in a concentration of 0.05 M.

The cathodic current density was 7 A.dm-2, the temperature of the bath 500C and its pH was 4.

The deposited layer had a content of molybdenum of 2.5 percent by weight, its internal stress was 28 MPa and its microhardness 500 HM.

Example 3 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum with the use of a halide contained nickel sulphosalicylate in a concentration of 0.75 M, nickel dibromide in a concentration of 0.05 M and disodium monomolybdate ina concentration of 0.013 M.

The cathodic current density was 5 A.dm-2, the temperature of the bath 500C and its pH was 4.

The deposited layer had a content of molybdenum of 6.11 percent by weight, its internal stress was 32 MPa and its microhardness was 597 HM.

Example 4 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum with a content of halide and of wetting agent contained nickel sulphosalicyate in a concentration of 0.75 M, nickel dibromide in a concentration of 0.05 M, disodium monomolybdate in a concentration of 0.01 M and disodium lauric sulphate in a concentration of 0.004 M.

The cathodic current density was 5 A.dml, the temperature of the bath 600C and its pH was 4.

The deposited layer contained molybdenum at 6.2 percent by weight, its internal stress was 40 and the microhardness 620 HM.

Claims

1. An aqueous electroplating solution which comprises nickel sulphosalicylate in a 0.1 to 1.05 M concentration, and a molybdenum salt in a 0.001 to 0.02 M concentration.

2. A solution according to claim 1, wherein the molybdenum salt is disodium monomolybdate.

3. A solution according to any preceding claim, which further comprises a nickel halide in a 0.01 to 0.2 M concentration.

4. A solution according to claim 3, wherein the nickel halide is nickel dibromide.

5. A solution according to any preceding claim, which further comprises an ionic or non-ionic surfactant in a 0.002 to 0.04 M concentration.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electrolyte for Cathodic Deposition of Alloys of Nickel with Molybdenum The invention concerns an electrolyte for cathodic deposition of alloys of nickel containing molybdenum. Such alloys of nickel with molybdenum produced in an electrolytic method are better than chemically pure nickel with regard to certain of their properties. The prior literature teaches that the nickel coatings have great internal stresses so that the deposition of thick layers is not possible. Moreover, the electroplating process has a very low cathodic current efficiency, especially in acidic solutions where it may only reach values of about 30%. The known electrolytes use nickel sulphate as a basic component. Further, they contain complex-producing materials, such as citric acid or tartaric acid and ammonia. Molybdenum may be used in the form of sodium monomolybdate. The present invention provides an aqueous electroplating solution which comprises nickel sulphosalicyiate in a 0.1 to 1.05 M concentration, and a molybdenum salt in a 0.001 to 0.02 M concentration. Preferably, the molybdenum salt is disodium monomolybdate. In order to adjust the solubilities, a nickel halide may also be included in a concentration of 0.01 to 0.2 M; nickel dibromide is preferred. Moreover, an ionic or non-ionic surfactant may be also incorporated in a concentration of 0.002 to 0.04 M; disodium lausic sulphate is preferred. Molybdenum may in general be in the form of a molybdate. It is not necessary, with regard to the complex-forming properties of the basic electrolyte, to add further complex-forming matter, such as organic hydroxy acids, which tend to deteriorate the properties of the coatings. The electrolyte results in a very low level of macrostress at a temperature above 400 C. The level of stress is further lowered with increasing temperature. The temperature is, in spite of the fact that the sulphosalicylate anion is also stable in aqueous solution at higher temperatures, limited however, by technologic problems, such as vaporization and corrosion. The cathodic current densities range between the limits from 1 to 10 A.dm-2 according to the conditions of the electrolysis.The cathodic current efficiency is higher than 90% with the pH values higher than 3. Embodiments of the electrolyte solution according to the invention are by the way of illustration shown in the following Examples. Example 1 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum contained nickel sulphosalicylate in a concentration of 0.8 M and disodium monomolybdate in a concentration of 0.01 M. The cathodic current density was 3 A.dm-2, the temperature of the bath 500C and its pH was 4. The deposited layer had a content of molybdenum of 7.5 percent by weight, its internal stress was 30 MPa and its microhardness 800 HM. Example 2 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum with the use of a halide contained nickel sulphosalicylate in a concentration of 0.75 M, disodium monomolybdate in a concentration of 0.005 M and nickel dibromide in a concentration of 0.05 M. The cathodic current density was 7 A.dm-2, the temperature of the bath 500C and its pH was 4. The deposited layer had a content of molybdenum of 2.5 percent by weight, its internal stress was 28 MPa and its microhardness 500 HM. Example 3 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum with the use of a halide contained nickel sulphosalicylate in a concentration of 0.75 M, nickel dibromide in a concentration of 0.05 M and disodium monomolybdate ina concentration of 0.013 M. The cathodic current density was 5 A.dm-2, the temperature of the bath 500C and its pH was 4. The deposited layer had a content of molybdenum of 6.11 percent by weight, its internal stress was 32 MPa and its microhardness was 597 HM. Example 4 The electrolyte for cathodic deposition of an alloy of nickel with molybdenum with a content of halide and of wetting agent contained nickel sulphosalicyate in a concentration of 0.75 M, nickel dibromide in a concentration of 0.05 M, disodium monomolybdate in a concentration of 0.01 M and disodium lauric sulphate in a concentration of 0.004 M. The cathodic current density was 5 A.dml, the temperature of the bath 600C and its pH was 4. The deposited layer contained molybdenum at 6.2 percent by weight, its internal stress was 40 and the microhardness 620 HM. Claims

6. A solution according to claim 5, wherein the surfactant is disodium lauric sulphate.

7. An aqueous electroplating solution substantially as disclosed in any Example.

8. A method of electroplating which employs the solution of any preceding claim.

9. An electroplated article whose coating comprises nickel and molybdenum in the ratio 0.1 to 1.05:0.001 to 0.02.