Indian scientists make headway for an eco-friendly process to enhance the anti-corrosiveness of high-strength aerospace aluminium alloys

Indian scientists have succeeded in developing an environment-friendly process for enhancing the anti-corrosive feature of high-strength aerospace aluminium alloys.

The aerospace, automobile and marine sector globally utilizes aluminium alloys as applications precisely for its strength-to-weight ratio (low density and high specific strength), while among varied aluminium alloys, heat treatable wrought alloy compositions possess high mechanical strength and are customarily preferred by the aerospace industry.

The aerospace parts made from these aluminium alloys, comprising landing gear, wing spar, fuselage, skins, pressure cabins and so on, are anticipated to influence high fatigue life and corrosion resistance.

The state-owned Autonomous Research and Development Centre of Department of Science and Technology’s, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) scientists found that the wear and corrosion resistance of aluminium alloys is strikingly strengthened by putting harder alumina coating through anodic-oxidation-based processes — anodising, hard anodising, and micro-arc oxidation (MAO).

Although, the MAO technique involves a dilute concentration of alkaline electrolyte, however, there is no emission of toxic fumes and the disposal of the exhausted electrolyte does not allure any environmental regulations. Hence, the MAO procedure is regarded as an eco-friendly process.

ARCI’s statement quoted: “The alumina coatings deposited through the MAO technique possess high hardness (1,000-1,900 HV), excellent wear, and corrosion resistance as compared to identically thick hard-anodised (HA) coatings (300-500 HV).”

The technology procedure entails bombardment of a component surface with spherical balls of a few hundred micrometres size, travelling at a specific kinetic energy. This occurs before the MAO coating (SP+MAO) depositions and leads to a ten-fold improvement in the fatigue life of aluminium alloys without distressing the wear and corrosion resistance of the coating.

The appearance of valuable full-scale residual stresses beneath the substrate-coating interface detains the crack proliferation and ensues in superior fatigue life that can be functional for lightweight aerospace structures.