Degradability of aluminum in acidic and alkaline solutions

• Aluminum was contacted with HCl, H2SO4, HNO3 and NaOH solutions under the same conditions.
• Higher aggressiveness of NaOH registered at lower concentration and lower temperature than HCl.
• A synergetic effect was observed with the mixture 4 M HCl + 4 M H2SO4.
• Nitrates played the role of inhibitors of Al dissolution in chlorides containing solutions.
• Examination of aluminum dissolution according to a heterogeneous model.

The processes of aluminum degradation in HCl, H2SO4, HNO3 and NaOH solutions were investigated in static and agitated media. The effects of concentration, temperature, and mixture of acids were studied. The dissolution of aluminum was faster in NaOH and HCl than in H2SO4 and HNO3. The activation energies were 86.5 and 52.4 kJ/mol for Al dissolved in HCl and NaOH respectively. An inhibiting effect on Al dissolution was observed with the mixture HCl + HNO3 regardless of the conditions used while a synergetic effect was observed with the mixture H2SO4 + HCl using acids at 4 M.

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