Electrochemical and spectroscopic studies on inhibition mechanism of benzyl thiocyanate for iron corrosion in 1 N perchloric and hydrochloric acid solutions

The inhibition mechanism of benzyl thiocyanate for iron corrosion in 1 N HClO 4 and 1 N HCl was investigated by polarization measurements and surface analyses. A protective film formed on the iron surface by the oxidative-addition reaction of the thiocyanate with iron was characterized using X-ray photo-electron and reflection Fourier Transform Infrared (FTIR) spectroscopy. A markedly high inhibition efficiency of this inhibitor was obtained for iron corrosion in 1 N HClO 4 at its high concentrations, as well as in H 2SO 4 previously reported, but not in 1 N HCl. Results of surface analyses suggested the formation of a protective layer composed of a ( η 3-benzyl) (thiocyanato) iron (II) complex on the surface in 1 N HClO 4. Since an unstable ( η 3-benzyl) (chloro) iron complex was formed in the layer, the anodic process of iron corrosion was stimulated in 1 N HCl, resulting in a moderate inhibition efficiency.