The inhibition effects of anion and cation inhibitors on corrosion of iron in an anhydrous acetonitrile solution of FeCl 3

Abstract

Corrosion of iron in an electrolytic anhydrous acetonitrile CH 3CN (ACN) containing FeCl 3 was investigated by polarization measurement and X-ray photoelectron and Fourier transform infrared reflection spectroscopies. The corrosion rate was markedly increased with the concentration of FeCl 3. Cathodic and anodic processes of iron corrosion in the ACN solution of FeCl 3 were reduction of Fe 3+ to Fe 2+ and Cl −-catalyzed iron dissolution, respectively. Bromide ion (Br −) mainly suppressed the anodic process of iron corrosion in the 0.01 M FeCl 3 ACN solution by chemical adsorption on the surface. Hexadecyl-trimethylammonium ion C 16H 33N CH 3 + 3 (C 16TMA +) was adsorbed on the negatively charged surface via an electrostatic interaction, resulting in inhibition of the cathodic process. An equimolar mixture of Br − and C 16TMA + suppressed both processes of iron corrosion in the 0.01 M FeCl 3 ACN solution by joint adsorption on the surface, indicating the synergism of inhibition.