Abstract
Corrosion characteristics of some commercially pure aluminum alloys (1060, 1100, 3003, and 5052) in different concentrations of nitric acid have been studied at different temperatures. Alloy 3003 exhibits maximum corrosion in all the acid concentrations followed by 5052, 1100, and 1060 alloys. The corrosion rate of aluminum is found to increase and decrease with time in 20 and 70% acid solutions, respectively. In the concentration range of 20–50% of the acid, all the alloys exhibited slightly passivating tendency during the potentiostatic anodic polarization. The breakdown potential 
of the alloys varies inversely with temperature, whereas an invariable enobling in steady‐state corrosion potential with rise in temperature is noted. The current density required for initiation of passivation, i.e. 
is related to temperature 
by
where 
and 
are constants. The alloys exhibited negative steady‐state corrosion potentials in a concentration range of 1–58% of the acid, but above this concentration positive values of the potentials have been noted. Variation of corrosion rates of the different alloys in different concentrations of the acid has been discussed in the light of the presence of different alloying elements. The influence of the addition of 0.025M, 0.05M, 0.1M, 0.25M, and 0.5M chloride, bromide, iodide, acetate, citrate, sulfate, and nitrate as their sodium salts has also been investigated on the anodic dissolution of 1060 alloy in 20% nitric acid. At concentrations of 0.025M, 0.05M, and 0.1M, Cl−, Br−, and I− have little noticeable effect, but at concentrations of 0.25M and 0.5M of the former two compounds very fast corrosion was recorded and the last compound appeared to be a corrosion inhibitor. The tolerable concentration of chloride ion increases with increase in the concentration of nitric acid in conformity with
Acetate, citrate, sulfate, and nitrate ions inhibit the dissolution of the alloy at all the concentrations used. It has been concluded that the sodium ion does not affect the dissolution tendency of the alloy and the anions are solely responsible for inhibiting the dissolution of the metal.