Patent ID: 7368019

Claim:
A method for precluding elution of nickel salt from a plumbing device made of a copper alloy that includes a valve and a tube coupling, comprising washing at least a liquid-contacting part of the plumbing device of a copper alloy containing nickel salt, with a cleaning fluid incorporating therein nitric acid and hydrochloric acid as an inhibitor under conditions of a temperature and a duration permitting effective removal of nickel salt, thereby effectively depriving a surface of the liquid-contacting part of nickel salt, and causing the hydrochloric acid to form a coating film on the surface of the liquid-contacting part and preclude elution of nickel salt, from the surface of the liquid-contacting part in the presence of the coating film, wherein the nitric acid has a concentration c in a range of 0.5 wt % <c<7 wt % and the hydrochloric acid has a concentration d in a range of 0.05 wt % <d<0.7 wt % in the cleaning fluid, wherein the temperature is set to 10° C.≦x≦50° C., and wherein nickel salt is removed with the cleaning fluid.