Inhibition efficiencies of some organic compounds on the corrosion of zinc in alkaline media

Purpose - The purpose of this paper is to investigate the inhibiting properties of six quaternary ammonium salts, three cationic surfactants and two non-ionic surfactants in 2 M KOH. An attempt also was made to correlate some molecular parameters of these compounds with their corrosion inhibitor efficiency. Design/methodology/approach - The inhibition efficiencies of quaternary ammonium salts, cationic surfactants and non-ionic surfactants on the corrosion of zinc in 2 M KOH solution were investigated by potentiodynamic polarisation, electrochemical impedance spectroscopy and linear polarisation methods. Findings - Inhibition efficiencies of quaternary ammonium salts were found to be due to physical absorption on the cathodic sides of zinc electrode and dependence of inhibition efficiencies on substituents were found. Physical adsorption of cationic surfactants on zinc electrode slowed down both anodic and cathodic reactions; thus they were found to be mixed type inhibitors. On the other hand, inhibition behaviour of non-ionic surfactants was found to be due to adsorption on zinc via polar groups. It was found that non-ionic surfactants behaved as mixed type inhibitors. Originality/value - Clarifies the role of molecular structure and substituents on the inhibition efficiency of surfactants and quaternary ammonium compounds on the corrosion of zinc in alkaline media.