EFFECT OF THIOCYANATE ON THE CORROSION AND PASSIVATION BEHAVIOR OF COPPER AND IRON - LASER RAMAN-SPECTROSCOPY AND PHOTOELECTROCHEMICAL STUDIES

The effect of small quantities (0.005-0.02 M) of added thiocyanate on the corrosion and passivation behavior of copper and iron in borate buffer solution (pH 8.4) was examined using cyclic voltammetry, laser Raman spectroscopy, and photoelectrochemical techniques. Anodic dissolution currents are significantly increased by the presence of SCN- and new surface phases are formed. Thiocyanate was found to cause passivity breakdown on iron but not on copper. Corrosion films of CuSCN, as well as Fe(II) and Fe(III) thiocyanates, have been identified spectroscopically. The surface coatings on Cu and Fe exhibited significant photoeffects. CuSCN was characterized to have p-type semiconductivity with a band gap of 2.9 eV and a flat band potential of -0.17 V vs sce in 0.01 M KSCN-borate buffer solution.