Electrolytic stripping bath and process

Claim 2

An electrolytic stripping bath for stripping metal deposits from a different basis metal comprising an aqueous solution having a pH of about 1 to about 14 and containing a halogen compound in an amount sufficient to activate the bath, a stripping component selected from the group consisting of (a) a bath soluble primary, secondary and/or tertiary amine having a carbon content of C 1 to C 8 , (b) a bath soluble inorganic nitrate and/or organic nitro compound and mixtures of (a) and (b), an inhibiting agent present in an effective amount to inhibit attack of the basis metal comprising a compound selected from the group consisting of glucoheptonic acid, malic acid, and mixtures thereof as well as the Group IA, IIA and ammonium salts thereof and at least one bath soluble compound selected from the group consisting of thiocyanates, oxalates and mixtures thereof.

Claim 3

The stripping bath as defined in claim 1 in which the thiocyanate said bath soluble compound includes the alkali metal and ammonium salts thereof.

Claim 4

The stripping bath as defined in claim 1 in which the thiocyanate said bath soluble compound comprises ammonium thiocyanate.

Claim 5

The stripping bath as defined in claim 2 in which the thiocyanate said compound is present in an amount of about 0.1 to about 20 g/l.

Claim 6

The stripping bath as defined in claim 2 in which the thiocyanate said compound is present in an amount of about 1 to about 5 g/l.

Claim 7

The stripping bath as defined in claim 2 in which the thiocyanate said compound is present in an amount of about 1 to about 2.5 g/l.

Claim 8

The stripping bath as defined in claim 2 in which said halogen compound is present in an amount up to about 12 g/l calculated as sodium bromide.

Claim 9

The stripping bath as defined in claim 2 in which said halogen compound comprises a bromine compound present in an amount of about 6 to about 10 g/l calculated as sodium bromide.

Claim 10

The stripping bath as defined in claim 2 further including a bath soluble cyanate compound in combination with said thiocyanate.

Claim 11

The stripping bath as defined in claim 9 in which said cyanate compound comprises an alkali metal cyanate salt, an ammonium cyanate salt and mixures thereof.

Claim 12

The stripping bath as defined in claim 9 in which said cyanate compound is present in an amount up to about 20 g/l.

Claim 13

The stripping bath as defined in claim 9 in which said thiocyanate is present in an amount of about 0.2 to about 0.8 g/l and said cyanate compound is present in an amount of about 2 g/l calculated as sodium cyanate.

Claim 14

The stripping bath as defined in claim 1 in which said oxalate compound is present in an amount up to its solubility in the bath.

Claim 15

The stripping bath as defined in claim 1 in which said oxalate compound is present in an amount of at least about 0.5 g/l.

Claim 16

The stripping bath as defined in claim 1 in which said oxalate compound is present in an amount of about 1 to about 4 g/l calculated as ammonium oxalate.

Claim 17

The stripping bath as defined in claim 1 in which the oxalate said compound comprises oxalic acid as well as the alkali metal and ammonium salts thereof.

Claim 18

The stripping bath as defined in claim 1 having a pH of about 5.5 to about 7.5.

Claim 19

A process for electrolytically stripping metal deposits such as copper, bright and semi-bright nickel, sulfamate nickel, nickel-phosphorous, cadmium, brass, tin, chromium and iron-nickel alloys from a different basis metal which comprises the steps of immersing an object to be stripped in a stripping bath comprising an aqueous solution having a pH of about 1 to about 14 and containing a halogen compound in an amount sufficient to activate the bath, a stripping component selected from the group consisting of (a) a bath soluble primary, secondary and/or tertiary amine having a carbon content of C 1 to C 8 , (b) a bath soluble inorganic nitrate and/or organic nitro compound and mixtures of (a) and (b); an inhibiting agent present in an effective amount to inhibit attack of the basis metal comprising a compound selected from the group consisting of glucoheptonic acid, malic acid, and mixtures thereof as well as the Group IA, IIA and ammonium salts thereof; and at least one bath soluble compound selected from the group consisting of thiocyanates, oxalates, and mixtures thereof, anodically charging the object and passing electric current through the solution to a cathode for a period of time to achieve the desired magnitude of stripping of the metal deposit from the object.

Claim 20

A process for electrolytically stripping metal deposits such as copper, bright and semi-bright nickel, sulfamate nickel, nickel-phosphorous, cadmium, brass, tin, chromium and iron-nickel alloys from a different basis metal which comprises the steps of immersing an object to be stripped in a stripping bath comprising an aqueous solution having a pH of about 1 to about 14 and containing a halogen compound in an amount sufficient to activate the bath, a stripping component selected from the group consisting of (a) a bath soluble primary, secondary and/or tertiary amine having a carbon content of C 1 to C 8 , (b) a bath soluble inorganic nitrate and/or organic nitro compound and mixtures of (a) and (b); an inhibiting agent present in an effective amount to inhibit attack of the basis metal comprising a compound selected from the group consisting of glucoheptonic acid, malic acid, and mixtures thereof as well as the Group IA, IIA and ammonium salts thereof; and at least one bath soluble compound selected from the group consisting of thiocyanates, oxalates, and mixtures thereof, anodically charging the object and passing electric current through the solution to a cathode for a period of time to achieve the desired magnitude of stripping of the metal deposit from the object.

Claim 21

The process as defined in claim 18 including the further step of controlling the temperature of said stripping bath within a range of about 60 to about 150° F.

Claim 22

The process as defined in claim 18 in which said bath soluble compound comprises a thiocyanate compound present in an amount of about 0.1 to about 20 g/l and including the further step of controlling the temperature of said stripping bath within a range of about 70° C. to about 100° F.

Claim 23

The process as defined in claim 20 in which said thiocyanate compound is present in an amount of about 1 to about 5 g/l.

Claim 24

The process as defined in claim 20 in which said different basis metal comprises steel and said metal deposit comprises an iron-nickel alloy or a sulfur-free nickel deposit and including the further step of controlling the electric current passing through the solution to an average current density of about 10 to about 200 ASF.

Claim 25

The process as defined in claim 18 including the further step of controlling the pH within a range of about 5.5 to about 7.5.

Claim 26

The process as defined in claim 18 in which said bath soluble compound comprises a thiocyanate compound and further including a bath soluble and compatible cyanate compound.

Claim 27

The process as defined in claim 24 in which said thiocyanate compound is present in an amount of about 0.1 up to about 20 g/l and said cyanate compound is present in an amount up to about 20 g/l.

Claim 28

The process as defined in claim 24 in which said thiocyanate compound is present in an amount of about 0.2 to about 1 g/l and said cyanate compound is present in an amount of about 1 to about 5 g/l.

Claim 29

The process as defined in claim 24 in which said thiocyanate compound is present in an amount of about 0.8 g/l calculated as ammonium thiocyanate and said cyanate compound is present in an amount of about 2 g/l calculated as sodium cyanate.

Claim 30

The process as defined in claim 18 in which said bath soluble compound comprises an oxalate compound present in an amount up to the solubility limit in said aqueous solution.

Claim 31

The process as defined in claim 28 in which said oxalate compound is present in an amount of about 1 to about 4 g/l.

Claim 32

The process as defined in claim 28 in which said halogen compound is present in an amount less than about 20 g/l calculated as sodium bromide.

Claim 33

The process as defined in claim 28 including the further step of interrupting the passing of electric current through the solution and withdrawing the object from the stripping bath and thereafter re-immersing the object in the stripping bath and again passing electric current through the solution to a cathode to achieve a further stripping of the metal deposit from the object.

Claim 34

The process as defined in claim 18 in which said bath soluble compound comprises a mixture of about 0.1 to about 20 g/l of a thiocyanate compound and about 0.5 to about 20 g/l of a cyanate compound.