Influence of substituent groups on performance of N -benzylidine phenylamine- N -oxide as corrosion inhibitor of mild steel in acidic solutions

Abstract

N-benzylidine phenylamine-N-oxide (nitrone) and eight of its derivatives with substituents in the para position of the α phenyl group were synthesised and their inhibition of the corrosion of mild steel in 1M HCl was investigated by weight loss, potentiodynamic polarisation studies, hydrogen permeation measurements, and impedance measurements. Determination of inhibition efficiency in the presence of these compounds at different temperatures clearly indicates that the dimethyl derivative shows the best performance even at temperatures as high as 70°C. Potentiodynamic polarisation studies clearly reveal the fact that nitrone and its derivatives act as mixed type inhibitors. All of these compounds are found to reduce the permeation of hydrogen through mild steel in HCl solution. Values of double layer capacitance and charge transfer resistance were derived from Nyquist plots obtained from ac impedance studies. The adsorption of these compounds on the mild steel surface obeys Temkin's adsorption isotherm.