Electrolytic method of and compositions for stripping electroless nickel
OwnerBarry W. Coffeyinventor
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Abstract
Electrolytic stripping solutions, which incorporate the novel use of oxoacids and/or oxoacid salts, and hydrogen peroxide, have been formulated for the rapid removal of electroless nickel from iron, steel, aluminum, and titanium alloys as well as other selected electrically conductive substrates. The formulations provide improved resistance to etching of the substrate and can be formulated to be free of chelates, chromates, nitrates, or concentrated acid solutions thereby increasing worker safety and reducing the cost of waste disposal of spent stripping solutions.
Claims21
A method for stripping electroless nickel deposits from a substrate selected from the group consisting of iron, cast iron, steel alloy, stainless steel, aluminum, electroplated nickel, cast nickel, iron/nickel/cobalt alloy, sulfamate nickel and titanium, the method comprising:
- a) immersing the substrate containing an electroless nickel deposit into a composition in an electrolytic bath, said composition comprising:
- i) a compound selected from the group consisting of oxoacids, oxoacid salts, and combinations thereof, and
- ii) hydrogen peroxide;
- and
- b) stripping the electroless nickel deposits from the substrate by electrolysis, wherein a hydrogen peroxide/acid mole ratio of at least 3.75 is maintained for strong oxoacids having one ionizable hydrogen and a dissociation constant of at least 2×10−1,
- wherein a hydrogen peroxide/acid mole ratio of at least 7.5 is maintained for strong oxoacids having at least two ionizable hydrogens, and
- wherein a hydrogen peroxide/acid mole ratio of at least 1.5 is maintained for weak oxoacids having a dissociation constant less than 2×10−1,
- with the proviso that, when aluminum is the substrate and strong oxoacids are used in the composition, said strong oxoacids are selected from the group consisting of sulfuric acid, sulfamic acid, their salts, and combinations thereof, and
- with the proviso that, when the substrate is selected from electroplated nickel, cast nickel, iron/nickel/cobalt alloy, and sulfamate nickel substrates, weak oxoacids, oxoacid salts, and combinations thereof are used in the composition.
A composition for electrolytically stripping electroless nickel deposits from a substrate, comprising:
- a) a compound selected from the group consisting of oxoacids, oxoacid salts, and combinations thereof, and
- b) hydrogen peroxide,
- wherein a hydrogen peroxide/acid mole ratio of at least 3.75 is maintained for strong oxoacids having one ionizable hydrogen and a disociation constant of at least 2×10−1,
- wherein a hydrogen peroxide/acid mole ratio of at least 7.5 is maintained for strong oxoacids having at least two ionizable hydrogen, and
- wherein a hydrogen peroxide/acid mole ratio of at least 1.5 is maintained for weak oxoacids having a dissociation constant less than 2×10−1.
A method for stripping electroless nickel deposits from a substrate selected from the group consisting of iron, cast iron, steel alloy, stainless steel, aluminum, electroplated nickel, cast nickel, iron/nickel/cobalt alloy, sulfite nickel and titanium, the method comprising:
- a) immersing a substrate containing an electroless nickel deposit into a composition in an electrolytic bath, said composition consisting essentially of
- i) a compound selected from the group consisting of oxoacids, oxoacid salts, and combinations thereof, and
- ii) hydrogen peroxide;
- and
- b) stripping the electroless nickel deposits from the substrate by electrolysis,
- wherein a hydrogen peroxide/acid mole ratio of at least 3.75 is maintained for strong oxoacids having one ionizable hydrogen and a dissociation constant of at least 2×10−1,
- wherein a hydrogen peroxide/acid mole ratio of at least 7.5 is maintained for strong oxoacids having at least two ionizable hydrogens, and
- wherein a hydrogen peroxide/acid mole ratio of at least 1.5 is maintained for weak oxoacids having a dissociation constant less than 2×10−1,
- with the proviso that, when aluminum is the substrate and strong oxoacids are used, said strong oxoacids are selected from the group consisting of sulfuric acid, sulfamic acid, their salts, and combination thereof, and
- with the proviso that, when the substrate is selected from electroplated nickel, cast nickel, iron/nickel/cobalt alloy, and sulfamate nickel substrates, weak oxoacids, oxoacid salts, and comnbinations thereof, are used in the composition.
A composition for electrolytically stripping electroless nickel deposits from a substrate, consisting essentially of:
- a) a compound selected from the group consisting of oxoacids, oxoacid salts, and combinations thereof;
- and
- b) hydrogen peroxide,
- wherein a hydrogen peroxide/acid mole ratio of at least 3.75 is maintained for strong oxoacids having one ionizable hydrogen and a dissociation constant of at least 2×1010−1,
- wherein a hydrogen peroxide/acid mole ratio of at least 7.5 is maintained for strong oxoacids having at least two ionizable hydrogens, and
- wherein a hydrogen peroxide/acid mole ratio of at least 1.5 is maintained for weak oxoacids having a dissociation constant less than 2×10−1.
Dependencies are inferred from the claim text.