Corrosion inhibition effect and adsorption behaviour of nicotinamide derivatives on mild steel in hydrochloric acid solution

Background A new class of nicotinamide derivatives viz., N-((1H-pyrrol-2-yl)methylene)nicotinamide, N-((methyl- (phenyl)amino)methylene)nicotinamide, N-nicotinoylbenzimidothioic acid and N-(4-(methylthio)benzylidene)nicotinamide have been synthesized and their corrosion inhibition effect on mild steel in 0.5 M HCl was investigated by mass loss, Tafel polarization technique and AC impedance measurements. Results The inhibition efficiency of the inhibitors on mild steel in 0.5 M HCl has been studied based on concentration, time interval and temperature. Potentiodynamic polarization studies showed that all the examined inhibitors suppress both anodic and cathodic process and behave as mixed type of corrosion inhibitors. Conclusions The adsorption of all the inhibitors was found to obey Langmuir isotherm model. Electrochemical impedance data revealed that polarization resistance (RP) increases and double layer capacitance (Cdl) decreases as the concentration of the inhibitors increases. FTIR, EDX and SEM analyses were performed to study the film persistency of the inhibitors.