Adsorption behavior and corrosion rate model of sodium carboxymethyl cellulose (Na-CMC) polymer on aluminium in HCl solution

Abstract

Adsorption behaviour and corrosion rate of Sodium carboxymethyl cellulose on aluminium was studied. Different concentration levels of Sodium carboxymethyl cellulose (Na-CMC) solution were applied on several prepared and polished aluminium coupons for a corrosion experiment. These coupons were totally immersed in 100ml of 0.5M solution of Hydrochloric acid (HCl) in an open beaker placed in a water bath at varying temperatures for 2-8hrs respectively. At every specified temperature and time interval, the immersed coupon specimen was withdrawn from the test solution, washed, dried and reweighed. The weight loss being the difference in weight of the specimen before and after immersion in the water bath was recorded for every coupon sample. The effects of concentration, temperature and time on corrosion rate were studied and from the various plots, it was observed that increase in the concentration of the inhibitor decreases the corrosion rate. The study of the adsorption behaviour showed that Na-CMC was physically adsorbed on the aluminium coupons and obeyed Freundlich adsorption isotherm with an activation energy of 32K.83j/mol and heat of adsorption of -18.21Kj/mol . The study also established a relationship between the corrosion rate, CR; concentration, C; temperature, T; and time t, through a mathematical model: CR = 3.8-⁵*T1.1617 - 0.00052t0.6176 - 0.0013C0.8012, the proportion of variance explained (R²) = 0.8658 (86.58%), From the Results of the experiment and the model, Na-CMC was found to be an active corrosion inhibitor of Aluminium in acidic environment.

Keywords: Adsorption, Aluminium, concentration, Corrosion Rate, Weight Loss