Effect of micro arc oxidation treatment on localized corrosion behaviour of AA7075 aluminum alloy in 3.5% NaCl solution
(1. Material Characterization Division, Materials and Metallurgy Group,
Vikram Sarabhai Space Centre, Thiruvananthapuram-695022, India;
2. International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad- 500005, India)
Vikram Sarabhai Space Centre, Thiruvananthapuram-695022, India;
2. International Advanced Research Centre for Powder Metallurgy and New Materials, Hyderabad- 500005, India)
Abstract: Alumina coating was formed on AA7075 aluminum alloy by micro arc oxidation (MAO) method and its corrosion and stress corrosion cracking (SCC) behaviors were examined in 3.5% (mass fraction) NaCl solution. Electrochemical impedance spectroscopy (EIS) was used to evaluate the degradation of the coating as a function of immersion time and was modeled with appropriate equivalent circuits. Constant load stress corrosion cracking (SCC) results followed by post-test metallographic observations demonstrated the usefulness of MAO coating to avoid the premature failure of the alloy due to severe localized corrosion initiated by Cu- and Fe-rich intermetallic phases.
Key words: aluminum alloy; micro arc oxidation; impedance spectroscopy; stress corrosion