Inhibition of corrosion of mild steel in acidic solutions by quarternary salts of pyridinium bases

The influence of pyridinium chloride (PC) and n‐hexa decyl pyridinium chloride (HDPC) on the corrosion of mild steel in 5N HCl and 5N H₂SO₄ has been studied using techniques such as weight loss and gasometric measurements, potentiodynamic polarisation studies, linear polarisation studies and small amplitude cyclic voltametric studies. It is found that HDPC is more inhibitive than PC and both the compounds perform better in H₂SO₄. Polarisation studies reveal that PC behaves as an anodic inhibitor in H₂SO₄ and as a mixed inhibitor in HCl. Measurements of values of polarisation resistance (R_p) and double layer capacitance (C_dl) in the presence of these compounds also reveal the better performance of HDPC in both the acids. The adsorption of PC and HDPC on a mild steel surface from both the acids is found to obey Temkin’s adsorption isotherm.