Effect of allyl triphenyl phosphonium bromide on electrochemical and corrosion behaviour of mild steel in 0·5M sulphuric acid

Phosphonium compounds are known to act as corrosion inhibitors of mild steel in acidic solutions. They may be added to hydraulic oils or drilling fluids to provide scale and corrosion inhibition. They can be applied on the substrate by immersion or be incorporated in a polymeric coating. In the present work, allyl triphenyl phosphonium bromide (ATTPB) is evaluated as the potential corrosion inhibitor for mild steel in sulphuric acid solutions. Galvanostatic polarisation and potentiostatic polarisation measurements were used to study the inhibition of mild steel corrosion in aerated 0·5M sulphuric acid at different temperatures by ATPPB. Corrosion potential, corrosion currents, cathodic and anodic Tafel slopes, heat of adsorption and effective activation energies have been calculated in the presence and absence of the ATPPB. Inhibition efficiency has been calculated for various concentrations at different temperatures to study the range of effectiveness of the ATPPB. It shows the inhibitor efficiencies in the range of 73 to 99% and performs best at 318 and 328 K. The nature of adsorption of ATPPB on the metal surface has also been examined using infrared spectroscopic studies. The results of surface morphology and quantum chemical analysis are in agreement with the electrochemical results.