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Electrochemical evaluation of 1-methyl-2,6-diphenyl-piperidin-4-one oxime as corrosion inhibitor for mild steel immersed in an sulphuric acid medium

K. Tharini, K. Raja and A. N. Senthilkumar

A novel corrosion inhibitor namely 1-methyl-2, 6-diphenyl piperidin-4-one oxime (MDPO) has been synthesized and its inhibitive performance towards the corrosion of mild steel in 1M sulphuric acid(H2SO4) was tested by weight loss study, electrochemical methods, SEM and theoretical studies. The weight loss studies were conducted at three different temperatures such as 30oC, 40oC and 50oC for various concentrations (0, 25, 50,100, 200 and 300 ppm) for 2h duration. The study revealed that inhibition efficiency increases with increase of MDPO concentration and decreases with increase of temperature. It was studied that MDPO adsorbs over alloy surface obeying Temkin’s isotherm. The calculated values of free energy of adsorption (DGads) support physisorption mechanism. Electrochemical parameters such as corrosion potential (Ecorr), corrosion current (icorr) and Tafel slopes (ba& bc) were determined using Tafel plot. The results showed that increase in concentration of MDPO decreases corrosion current and behave as mixed mode inhibitor. AC impedance measurement as determined by Nyquist plot revealed that charge transfer resistance increases with increase of concentration, whereas double layer capacitance decreases with increase of concentration tribute each other. SEM studies revealed the film forming ability of MDPO in H2SO4 medium. Quantum chemical studies exemplified that the electrons present in the phenyl ring of MDPO assist largely in the corrosion control process