Study on Surface Passivation Technology and Properties of Copper Alloy for Building Decoration

Different conversion films were prepared on the surface of H62 copper alloy for decoration by the chemical impregnation method,and the passivation solution formulations of single rare earth salt and composite(Ce+La) salt conversion films were optimized.The corrosion resistance and mechanism of the samples without rare earth salt,single Ce salt,single La salt,and (Ce+La) salt were compared and analyzed.The results show that the conversion film with 8%lanthanum nitrate/cerium nitrate in the passivation solution of single rare earth salt has the best corrosion resistance;the optimal passivation process of composite (Ce+La) salt is lanthanum nitrate/cerium nitrate=4/4 g/L,C₆H₅N₃ concentration 15 g/L,Na₂MoO₄ concentration 2 g/L,C₆H₈O₇ concentration 13 g/L,C₇H₆O₆S.2H₂O concentration 9 g/L,SDBS concentration 0.2 g/L,passivation temperature 48℃,passivation time 4min.The results of nitric acid drop,neutral salt spray,static immersion corrosion,and electrochemical corrosion test of different conversion film samples are consistent;that is,the order of the resistance from low to high is:without rare earth salt<single Ce salt<single La salt<(Ce+La) salt,adding rare earth salt in the passivation solution will help to improve the thickness of the conversion film and enhance the corrosion resistance of the conversion film,and the composite addition of (Ce+La) salt can obtain a better passivation effect compared with single rare earth salt.