Investigation of Inhibition Potential Effect of Organic Compound for the Corrosivity of Phosphoric Acid on Aluminium

The organic compound used as corrosion inhibitor was benzaldehyde. The use of organic compounds as corrosion inhibitors is of potential interest due to their abundant availability, cost effectiveness, and environmental acceptability. However, this study investigates the inhibition effect of this organic compound (benzaldehyde) on the corrosion of aluminium in phosphoric acid solution. Experiments were performed by varying the temperature and concentration of the compound under study. The results obtained from the study shows that the organic compound (benzaldehyde) is a potential inhibitor for the corrosion of aluminium in phosphoric acid solution. The inhibition efficiency was found to increases progressively as the concentration of the inhibitor increases but decreases when the temperature rises. Activation energy values for the corrosion process was found to be 32.61 kJ/mol in uninhibited phosphoric acid solution which increased to 49.53 kJ/mol in the presence 0.1 M concentration of the inhibitor. The values of the rate constant and half live were 9.12 × 10-3 hr-1 and 75.94 hr in uninhibited phosphoric acid solution which changed to 4.56× 10-3 and 151.80 hr in the presence of 0.1 M inhibitor concentration. Kinetics of the reaction in uninhibited and in the presence of the inhibitor revealed that the process follows a first order reaction. The evaluated enthalpy (ΔH) gave positive values which indicate that the heat of adsorption process on the surface of aluminum was endothermic. The negative values of entropy (ΔS) signified that the activated complex at the rate determining step is an association, not dissociation. Evaluated values of free energy of adsorption (ΔGads) were all negative, implying spontaneity of the process and were around and less than -20 kJ/mol, indicative of physisorption of the adsorption process.