SULFURIZATION COLORING METHOD FOR COPPER AND COPPER ALLOY

PROBLEM TO BE SOLVED: To stably execute coloring treatment of high performance and high quality even if activating treatment for a copper material is obviated by using a sulfurization coloring soln. contg. potassium sulfide and sodium hydroxide by specified concn. SOLUTION: The copper material as the object may has a planar shape or the other shape such as of an ornament. The sulfurization coloring soln. is composed of an aq. soln. incorporating of potassium sulfide by the concn. of 3 to 20 g/l and sodium hydroxide by the concn. of >60 g/l. There is a need of controlling the pH of the sulfurization coloring soln. to >=14 for imparting the function of removing the factor of inhibiting coloring reaction to the sulfurization coloring soln. By controlling the concn. of potassium sulfide or the dipping time of the copper member into the sulfurization coloring soln., the color tone of black, brown, light brown or the like can be obtd. As to the soln. temp. at which the sulfurization coloring is executed, there is no problem only if it lies in the range from 10 to 60 deg.C. Moreover, there is no occurrence of precipitation in this sulfurization coloring soln. Furthermore, since the decomposing rate of the soln. is slow, the service life of the soln. is prolonged.