Corrosion Resistance of Aluminium in 0.5 M H_2SO_4 in the Presence of Cassia fistula Extract

摘要

The effect of Cassia fistula leaves extract on the corrosion of Al in 0.5 M H_2SO_4 at 30°C was investigated using gravimetric and electrochemical method. Gravimetric tests were conducted for 32 days in inhibited and uninhibited test solutions, while the potentiodynamic polarization tests were conducted from an anodic and cathodic potential of +0.5 V and -1.0 V respectively, at a scan rate of 0.1 V/s. Result analyses showed that Cassia fistula inhibits corrosion of Al effectively and adsorbs according to Langmuir adsorption isotherm. Corrosion rate reduced as inhibitor concentration increased for the gravimetric method, whereas for the electrochemical method it reduced as concentration increased, with exception at 4 and 6 g/L inhibitor concentration. Adsorption was found to be spontaneous for both techniques, while the inhibition mechanism was found to be mixed but predominantly cathodic. Cassia fistula boosted thin oxide film surface coverage to hinder attack of the sulphuric acid.