Inhibition of the corrosion of pure aluminium in hydrochloric acid solutions

The corrosion rates and inhibitor efficiencies have been determined for 99.5% aluminium in hydrochloric acid solutions, with the following inhibitors : acridine, thiourea, nicotinic acid, dextrin and tannic acid, of which acridine is the best. Polarisation studies with thiourea show that anodic polarisation is negligible, whereas cathodic polarisation is considerable, so that the corrosion process with this inhibitor appears to be essentially under cathodic control.