Electrodeposition of Hard Magnetic Coatings

1 . An aqueous electrolytic plating solution comprising:

a) a source of nickel ions;

b) a source of cobalt ions;

c) a source of phosphite ions;

d) an amino acid; and

e) optionally, boric acid.

2 . The aqueous electrolytic plating solution according to claim 1 , wherein the source of nickel ions is a nickel salt.

3 . The aqueous electrolytic plating solution according to claim 2 , wherein the nickel salt comprises nickel sulfate or nickel chloride.

4 . The aqueous electrolytic plating solution according to claim 1 , wherein the concentration of nickel ions is between about 10 to about 30 g/L.

5 . The aqueous electrolytic plating solution according to claim 1 , wherein the source of cobalt ions is a cobalt salt.

6 . The aqueous electrolytic plating solution according to claim 5 , wherein the cobalt salt comprises cobalt sulfate or cobalt chloride.

7 . The aqueous electrolytic plating solution according to claim 1 , wherein the concentration of cobalt ions is between about 5 to about 15 g/L.

8 . The aqueous electrolytic plating solution according to claim 1 , wherein the ratio of nickel ions to cobalt ions is between about 1:1 to about 6:1.

9 . The aqueous electrolytic plating solution according to claim 8 , wherein the ratio of nickel ions to cobalt ions is between about 2:1 to about 3:1.

10 . The aqueous electrolytic plating solution according to claim 1 , wherein the source of phosphite ions comprises sodium phosphite, potassium phosphite or phosphorus acid.

11 . The aqueous electrolytic plating solution according to claim 1 , wherein the concentration of phosphite ions is between about 2 to about 9 g/L.

12 . The aqueous electrolytic plating solution according to claim 1 , wherein the amino acid has the formula:

H 2 N—CHR—CO 2 X

wherein R is H or a (C 1 to C 4 alkyl and X is H or an alkali metal cation.

13 . The aqueous electrolytic plating solution according to claim 12 , wherein the amino acid is one or more of glycine, alanine, valine, leucine, iso-leucine, or salt of any of the foregoing.

14 . The aqueous electrolytic plating solution according to claim 13 , wherein the amino acid is glycine.

15 . The aqueous electrolytic plating solution according to claim 12 , wherein the concentration of the amino acid is between about 0.1 g/L to about 15 g/L.

16 . The aqueous electrolytic plating solution according to claim 15 , wherein the concentration of the amino acid is between about 2 to about 8 g/L.

17 . The aqueous electrolytic plating solution according to claim 16 , wherein the concentration of the amino acid is between about 4 and about 6 g/L.

18 . The aqueous electrolytic plating solution according to claim 1 , wherein the boric acid is present at a concentration of between about 25 to 35 g/l.

19 . The aqueous electrolytic plating solution according to claim 1 , further comprising one or more salts capable of increasing the conductivity of the aqueous electrolytic plating solution.

20 . The aqueous electrolytic plating solution according to claim 19 , wherein the one or more salts are selected from the group consisting of ammonium chloride, ammonium sulfate, potassium sulfate, potassium chloride, sodium chloride and sodium sulfate.

21 . The aqueous electrolytic plating solution according to claim 1 , wherein the plating solution has a pH of between about 3 and 4.

22 . A method of electrodepositing a cobalt/nickel/phosphorus alloy on an electrically conductive substrate, the method comprising the steps of:

passing a plating current through the substrate as a cathode in an aqueous electrolytic plating solution, wherein the aqueous electrolytic plating solution comprises:

a) a source of nickel ions;

b) a source of cobalt ions;

c) a source of phosphite ions;

d) an amino acid; and

e) optionally, boric acid,

to deposit the cobalt/nickel/phosphorus alloy on the electrically conductive substrate.

23 . The method according to claim 23 , wherein the source of nickel ions comprises nickel sulfate or nickel chloride.

24 . The method according to claim 22 , wherein the concentration of nickel ions is between about 10 to about 30 g/L.

25 . The method according to claim 22 , wherein the source of cobalt ions comprises cobalt sulfate or cobalt chloride.

26 . The method according to claim 22 , wherein the concentration of cobalt ions is between about 5 to about 15 g/L.

27 . The method according to claim 22 , wherein the ratio of nickel ions to cobalt ions is between about 1:1 to about 6:1.

28 . The method according to claim 27 , wherein the ratio of nickel ions to cobalt ions is between about 2:1 to about 3:1.

29 . The method according to claim 22 , wherein the source of phosphite ions comprises sodium phosphite, potassium phosphite or phosphorus acid.

30 . The method according to claim 22 , wherein the concentration of phosphite ions is between about 2 to about 9 g/L.

31 . The method according to claim 22 , wherein the amino acid has the formula:

H 2 N—CHR—CO 2 X

wherein R is H or a C 1 to C 4 alkyl and X is H or an alkali metal cation.

32 . The method according to claim 31 , wherein the amino acid is one or more of glycine, alanine, valine, leucine, iso-leucine, or salt of any of the foregoing.

33 . The method according to claim 32 , wherein the amino acid is glycine.

34 . The method according to claim 31 , wherein the concentration of the amino acid is between about 0.1 g/L to about 15 g/L.

35 . The method according to claim 34 , wherein the concentration of the amino acid is between about 2 to about 8 g/L.

36 . The method according to claim 22 , wherein the boric acid is present at a concentration of between about 25 to 35 g/1.

37 . The method according to claim 22 , further comprising one or more salts capable of increasing the conductivity of the aqueous electrolytic plating solution, wherein the one or more salts are selected from the group consisting of ammonium chloride, ammonium sulfate, potassium sulfate, potassium chloride, sodium chloride and sodium sulfate.

38 . The method according to claim 22 , wherein the aqueous electrolytic plating solution has a pH1 of between about 3 and 4.

39 . The method according to claim 22 , wherein the plating current has a current density of between about 0.25 and about 1.5 ASD.

40 . The method according to claim 22 , wherein the aqueous electrolytic plating solution is maintained at a temperature of between about 15° C. to about 35° C.

41 . An article coated by the process of claim 22 .

42 . The article according to claim 41 , wherein the cobalt/nickel/phosphorus alloy has a composition of between about 65 wt. % to about 85 wt. % cobalt, about 13 wt. % to about 33 wt. % nickel and about 1.2 wt. % to about 2.5 wt. % phosphorus.

43 . The article according to claim 41 , wherein the coating has a coercivity of about 344 to about 741 Oersteds.

44 . The article according to claim 41 , wherein the coating has a remanence of about 0.8 to about 1.17.