The corrosion rate of aluminium in the orthophosphoric acid solutions in the presence of sodium molybdate

The influence of the Na2MoO4 initial concentration on the corrosion rate of aluminium in the H3PO4 solution (0.5, 1, 2 M) between 290 and 323 K was studied using a gasometric technique. Inhibition efficiency was calculated. Depending on the initial concentration of Na2MoO4 the inhibition mechanism was either the adsorption of the inhibitor onto the surface of metal or the adsorption together with the formation of the conversion coatings. The solutions of 1 M H3PO4, 50 mM Na2MoO4 may be applied to determine the mass per unit area and thickness of anodic coatings.