The electrodeposition of metals from their trifluoroacetate-amide baths

Abstract

This paper will deal with the electrodeposition of copper and nickel from the Cu(CF 3COO) 2-HCONH 2 bath, Ni(CF 3COO) 2-HCONH 2 bath, Cu(CF 3COO) 2-HCON(CH 3) 2 bath and Ni(CF 3COO) 2-HCON(CH 3) 2 bath. The properties of these baths and the mechanism of the electrodeposition of copper and nickel from these baths were studied. While solvolysis occurs in the HCONH 2 bath, it does not occur in the HCON(CH 3) 2 bath. A complex is formed in each bath. Since the bond between the metallic ion and the solvent in the HCON(CH 3) 2 bath is stronger than that in the HCONH 2 bath, and since the dielectric constant of the solvent in the former is also lower than in the latter, is difficult to electrodeposit metal and Cu 2O is formed at cathode in the Cu(CF 3COO) 2-HCON(CH 3) 2 bath. The specific conductance in the HCON(CH 3) 2 bath is lower than that in the HCONH 2 bath. It is possible to obtain a better copper electrodeposit over a wider range of current density in the Cu(CF 3COO) 2- HCON(CH 3) 2 bath containing citric acid than in the same bath containing no citric acid. This range almost coincides with that in the Cu(CF 3COO) 2-HCONH 2 bath. While it is possible to obtain better nickel electrodeposit in Ni(CF 3COO) 2-HCONH 2 and Ni(CF 3COO) 2-HCON(CH 3) 2 baths containing appropriate additives, the range of current density which permits one to obtain a superior electrodeposit in the latter bath is narrow. The electrodeposit of nickel or copper obtained from the HCONH 2 and HCON(CH 3) 2 baths has a granular structure. The values of η c E c , and b c in the copper electrodeposition reaction from the Cu(CF 3COO) 2-HCON(CH 3) 2-200 g/l citric acid bath are higher than those in the same reaction from the Cu(CF 3COO) 2-HCONH 2 bath, while the values of i oc and α c are lower, so the electrodeposition of copper from the former can be said to be more difficult. On the other hand, the value of n is always about 1 for both the baths. It may be concluded in view of this fact that the deposition of copper from HCONH 2 and HCON(CH 3) 2 baths takes place through Cu + and that the deposition of nickel from HCONH 2 bath takes place through Ni +.