ION-PAIRING AS A METHOD OF CONTROLLING THE COMPOSITION OF ELECTRODEPOSITED ALLOYS

A study was made of the possibility of controlling the composition of electrodeposited alloys by the use of noncomplexing ion-pairing salts. It was shown both voltammetrically and by analysis of electrodeposits that the additin of ion-pairing cations increased the rate of deposition of tin significantly (because of ion-pairing with the negative stannite or stannate ion) and slightly decreased the rate of depositoin of the positively charged copper. As a consequence of this, the addition of tetrabutylammonium perchlorate increased the ratio of tin to copper in the deposit. The lowering of the dielectric constant of the solution by addition of tert-butyl alcohol increased the ion-pairing and, thus, increased this effect. Similarly, it was shown that the quaternary salt increased the current efficiency for depositi of tin and slightly decreased the current efficiency for deposition of copper.