Patent ID: 8182879

Claim:
A method for preventing elution of nickel from a water-contact instrument made of copper alloy and plated with a material containing nickel, which comprises applying a protective film formation agent which comprises a protective film formation component consisting essentially of a benzotriazole having a hydrophilic group and a straight-chain fatty acid, and an organic solvent for dissolving the component in water, to a surface of a nickel coat that wraps around and adheres to at least a water-contact surface of the water-contact instrument to form a protective film; and drying to intimately bond the protective film to the surface of the nickel coat; wherein the protective film consists essentially of the benzotriazole having a water-repellent outside and an inside having said hydrophilic group bonded intimately to the nickel coat and the straight-chain fatty acid having an inside having a hydrophilic group bonded intimately to the nickel coat, thereby suppressing elution of nickel with the protective film.