Enthone Incorporated

Frank A Brindisi, Jr

Thomas E Sullivan

Thomas W Bleeks

Improved solutions are provided for selectively stripping alloys containing nickel with gold, phosphorous or chromium from substrates formed from alloys containing iron with chromium and in some instances nickel, or nickle rich, chromium bearing alloys, some of which also contain iron. These solutions comprise concentrated nitric acid, at least one chloride salt, an organic corrosion inhibitor and, optionally, an organic surface active agent. An improved method utilizing the solutions of the invention is also provided and facilitates stripping of these alloys in substantially reduced time, without degradation of the underlying substrate.

Solution and method for selectively stripping alloys containing nickel

Acidic solutions for selectively stripping tin or tin-lead alloys from copper substrates comprising an aqueous solution of at least one nitro-substituted aromatic compound; an inorganic acid capable of readily reacting with tin and lead to form water-soluble salts thereof and incapable of reacting with tin and lead to form a water-insoluble compound film on the tin or tin-lead alloy surface, preferably fluoboric acid; a thiourea; an organic acid of the formula RCOOH wherein R is 1-2C alkyl or hydrogen; and a haloacetic acid wherein the halogen is chloro or bromo. The haloacetic acid in combination with the acid of the formula RCOOH result in a pronounced synergism in accelerating the rate of stripping the tin or tin-lead alloy deposit from the copper substrate.

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Madison, CT, United States of America

Frank A Brindisi, Jr