Study of corrosion inhibition of mild steel in sulphuric acid medium by 1,3,3-trimethyl-2,6-diphenyl piperidin-4-one oxime

摘要

Surface protecting ability of 1, 3, 3-trimethyl -2, 6-diphenyl piperidin-4-one oxime (TPO) against mild steel (MS) in 1M sulphuric acid medium has been investigated by weight loss study, electrochemical methods, SEM and theoretical studies. The weight loss studies were conducted at four different temperatures such as 30oC, 40oC and 50oC for various concentrations of (0, 50, 100, 200, 300 400 and 500 ppm) for 2h duration. The study showed that inhibition efficiency increased with increase of TPO concentration and decreased with increase of temperature. It was found that inhibition was due to adsorption of TPO on the MS surface obeying Temkin’s adsorption isotherm. The calculated values of free energy of adsorption (DGads) support physisorption mechanism. Electrochemical data for corrosion processes such as corrosion potential(Ecorr), corrosion current(icorr) and Tafel slopes (ba& bc) were determined using Tafel plot, which showed that increase in concentration of TPO decreases corrosion current and behaves 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 complimenting each other. SEM studies revealed the surface protecting ability of TPO in H2SO4 medium. Quantum chemical studies illustrated that the corrosion inhibition efficiency of TPO is due to the electrons of phenyl ring.