Blends of polyvinyl pyrrolidone and polyacrylamide as corrosion inhibitors for aluminium in acidic medium

Abstract

The corrosion and inhibition behaviour of aluminium in hydrochloric acid (HCl) in the absence and presence of polyvinyl pyrrolidone (PVP), Polyacrylamide (PA) and their blends was studied in the temperature range of 30 – 60oC using weight loss, hydrogen evolution and thermometric techniques. The inhibition efficiency (%I) increased with increase in inhibitors concentration. Increased in temperature led to increase in corrosion rate but decreased the inhibition efficiency PVP was found to have the higher inhibition efficiency than PA which may suggest that the differences in their molecular structures play a significant role in the adsorption and hence inhibition process. Inhibition efficiency was enhanced on blending the two polymers; the optimum inhibition efficiency was obtained at 3:1 blending ratio for PVP: PA. The inhibitors (PVP and PA) obey Freundlich, Temkin and Flory-Huggins adsorption isotherms at all the temperatures. Results obtained from the kinetic and thermodynamic parameters indicate spontaneous adsorption of the inhibitors unto aluminium surface following physical adsorption mechanism.