THE CORROSION OF SILVER, COPPER, PALLADIUM AND GOLD BY FE(III) AND CU(II) IN DIMETHYLSULFOXIDE AND WATER SOLUTIONS

A detailed study has been made of the mechanisms of the corrosion of copper, silver, palladium and gold by iron(III) and copper(II) in chloride and bromide media in both aqueous and dimethylsulphoxide (DMSO) solutions. The mechanisms were elucidated by rotating disc methods. In the absence of complicating factors such as surface film formation, observed corrosion potentials were found to be in good agreement with those predicted from separate studies of the anodic and cathodic half-reactions. All of the metals studied, with the possible exception of copper, are more readily corroded in DMSO solutions. Furthermore, the corrosion rates in DMSO are in general cathodic-diffusion controlled, ie, they are limited only by the rate of mass transfer of the oxidant [Fe(III) or Cu(II)] to the metal surface. In contrast, the aqueous corrosion reactions are often complicated by surface film formation. The implications of these findings for the hydrometallurgical processing of these metals are briefly discussed.