Inhibitive efficiency of sulphathiazole for aluminum corrosion in trichloroacetic acid

Purpose - The purpose of this paper is to investigate the effect that different concentrations of the inhibitor sulphathiazole have on the corrosion of aluminum in 0.01, 0.05 and 0.10 M trichloroacetic acid (TCA), and to elucidate the mechanisms of inhibition for this system. Design/methodology/approach - Gravimetric measurements and galvanostatic polarization were used to investigate the effect of sulphathiazole on the corrosion of aluminum in TCA solution. The findings were used to determine the corrosion rates and efficiencies of the inhibitor at different concentrations. Findings - The corrosion rate of aluminum decreased with increasing inhibitor concentrations and the efficiency of inhibition increased with increasing concentration of inhibitor up to almost 89 percent in 0.01 M TCA and up to 65.87 percent in 0.10 M TCA. The concentrations of inhibitor were in the range of 5-20 mM. Absorption of the inhibitor was onto the aluminum surface and consistent with the Langmuir adsorption isotherm. A plot of log (theta/1 - theta) versus log C gave a straight line, which suggests that the inhibitor covers both the anodic and cathodic regions. From the plot of the isotherm, it was observed that one inhibitor molecule occupies more than one active site. The mean Delta G(ads)(0) values were negative almost in all cases, indicating that the adsorption was spontaneous and that the mechanism of adsorption was physical - i.e. electrostatic attraction. Polarization data revealed that the inhibitor functions as a mixed inhibitor. Originality/value - The paper deals with the inhibition of corrosion of 25 commercially pure aluminum in 0.01, 0.05 and 0.10 M solutions of TCA. To date, not much detailed information has been generated about this problem.