DERIVATIVES OF BENZOIC ACID AS CORROSION INHIBITORS FOR 1060 ALUMINIUM IN 1% HYDROCHLORIC ACID CONTAINING 10 PPM TUNGSTATE IONS

摘要

The inhibitive effect of benzoic acid and hydroxy benzoic acids (namely o- & p-hydroxy benzoic acid) and methoxy benzoic acids (namely m- &-p-methoxy benzoic acids) on the corrosion of 1060 aluminium in hydrochloric acid containing tungstate ions has been studied at different concentrations. Both weight loss method and polarisation method (i.e., electrochemical techniques) have been used to find the inhibition efficiency of the inhibitors, at various concentrations of inhibitors, and at two temperature studied (35℃ & 45℃) for 24 hours immersion period. The efficiency of inhibitors increases with concentration and decreases with increase in temperature. o-Hydroxy benzoic acid is found to be the most efficient inhibitor among all inhibitors studied. All inhibitors obey Langmuir adsorption isotherm equation. Both cathode as well as anode are polarized which indicate a mixed type of inhibition. Values of activation energy and heat of adsorption for the system studied reveal the fact that the inhibitor adsorption (involving chemical forces rather than physical forces) appears to be responsible for the inhibition of corrosion. The inhibitors are found to retard the corrosion of 1060 aluminium alloy by acting on its cathodic and anodic sites.