Corrosion Characteristics of Some Aluminum Alloys in Nitric Acid

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 Eh 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. Ic is related to temperature T by logI,.= a + bT where a and b 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, CI-, 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 log Ca~ = a + b log Cp~ 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.

Steam assisted oxide growth on aluminium alloys using oxidative chemistries: Part I Microstructural investigation

“…However, the passivating nature of HNO 3 contrary role leading to competing process of oxide growth and dissolution of aluminium. The increase in the concentration of HNO 3 helps to develop a passive film more rapidly than the dissolution of aluminium as reported in literature [28]. Literature shows that [30,31] aluminium dissolution increases with decrease in the concentration of NO 3 − indicating that an optimal inhibition of metal occurs when the concentration of passive agents exceeds a certain value.…”

“…However, the pH value is not the single parameter to be considered when predicting the stability and formation of oxide film in a media like nitric acid [27]. The passivating nature of the HNO 3 acid on aluminium is very well known [28]. However, the passivating nature of HNO 3 contrary role leading to competing process of oxide growth and dissolution of aluminium.…”

Corrosion behaviour of aluminium in hydrochloric acid (HCl) solution containing mercaptoacetic acid

“…It is well known [21] that aluminium relies on the presence of surface oxide film for its corrosion resistance. This film forms almost instantly on exposure to air.…”

Characterization of 2024 T3 Aluminum Alloy after Rare Earth Desmutting

“…The anodic dissolution is facilitated by the microgalvanic coupling between the particles and the matrix; it is assisted by Cl − ions that penetrate / attack the alumina film. [23][24][25] Al-Kharafi and Badawy found a significant decrease of the corrosion resistance of Cu-containing aluminum alloys with increase of the chloride ion concentration (>35 mM) in nitric acid solution. 26,27 The presence of copper in the alloys increases the attack by Cl − ions due to the formation of oxyhalide complexes that may cause the natural passivity to decrease.…”