Corrosion inhibition of aluminum alloy 3SR in HCl by polyvinylpyrrolidone and polyacrylamide: Effect of molecular structure on inhibition efficiency

The inhibitive performance of two water soluble polymerspolyacrylamide (PA) and polyvinylpyrrolidone (PVP) on the corrosion behavior of aluminum alloy 3SR in HCl solution was investigated using weight loss, hydrogen evolution, and thermometric methods at 3060°C. Results obtained indicate that both polymers inhibited acid-induced corrosion of aluminum at the temperatures studied. PVP was found to be a better corrosion inhibitor than PA. All measurements from the three techniques show that inhibition efficiencies increase with increase in inhibitor concentration and decrease with increase in temperature. This indicates that the inhibitive actions of the polymers were mainly due to adsorption. Adsorption of these inhibitors follows Temkin and El-Awady adsorption isotherm models. Kinetic/thermodynamic parameters (E_a, K_ads, ΔG^o_ads} of adsorption of the studied inhibitors reveal that the adsorption was physical in nature and spontaneous. Differences in inhibition efficiency of the two polymers could be linked to their differences in molecular structure.