Abstract
Butyl triphenyl phosphonium bromide (BuTPPB) has been evaluated as a corrosion inhibitor for mild steel in 0.5 M H 2SO 4 solutions using galvanostatic polarisation and potentiostatic polarisation measurements. The study was also complemented by infra red (IR) spectroscopy, scanning electron microscopy (SEM) and quantum chemical calculations. Galvanostatic polarisation measurements showed that the presence of BuTPPB in aerated 0.5 M H 2SO 4 solutions decreases corrosion currents to a great extent and the corrosion rate decreases with increasing inhibitor concentration at a constant temperature. At 298K, inhibition efficiency was found to be 94.5% for 10 −7 M BuTPPB which increased to about 99% for the BuTPPB concentration of 10 −2 M. The effect of temperature on the corrosion behaviour of mild steel was studied at five different temperatures ranging from 298 to 338K. The polarisation curves clearly indicate that BuTPPB acts as a mixed type inhibitor. Adsorption of BuTPPB on the mild steel surface follows the Langmuir isotherm. Potentiostatic polarisation measurements showed that passivation was observed only for lower BuTPPB concentrations (10 −5 and 10 −7 mol l −1) for the mild steel in 0.5 M H 2SO 4. IR and SEM investigations also confirmed the adsorption of BuTPPB on the mild steel surface in 0.5 M H 2SO 4 solutions. The molecular parameters obtained using PM3 semi-empirical method, were correlated with the experimentally measured inhibitor efficiencies.
Published Version
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