METHOD FOR MAINTAINING PLATING CAPACITY IN ELECTROLESS GOLD PLATING BATH

A method for stably maintaining and managing the plating capacity of an electroless gold plating bath for a long time is provided to obtain gold plating film with good external appearance without causing flaws in the external appearance according to the progress of intergranular corrosion on a nickel surface, and a method for maintaining and managing, stably for a long time, an electroless gold plating bath in which gold cyanide salt has been consumed by plating treatment is provided. As a method for maintaining and managing the plating capacity of the electroless gold plating bath in a state that an electroless gold plating bath is maintained at a temperature of 70 to 90 deg.C, the electroless gold plating bath containing gold cyanide salt, complexing agent, formaldehyde-sodium bisulfite adduct, and amine compound represented by a formula 1, R1-NH-C2H4-NH-R2, or formula 2, R3-(CH2-NH-C2H4-NH-CH2)n-R4, where R1, R2, R3 and R4 denote -OH, -CH3, -CH2OH, -C2H4OH, -CH2N(CH3)2, -CH2NH(CH2OH), -CH2NH(C2H4OH), -C2H4NH(CH2OH), -C2H4NH(C2H4OH), -CH2N(CH2OH)2, -CH2N(C2H4OH)2, -C2H4N(CH2OH)2, or -C2H4N(C2H4OH)2, the R1, R2, R3 and R4 being the same as or different from each other, and n is an integer of 1 to 4, the method for maintaining and managing the plating capacity of the electroless gold plating bath comprises regularly supplying alkali cyanide, formaldehyde-sodium bisulfite adduct, and an amine compound as first supply components.