Review of coatings used for corrosion protection of aluminium alloys

Aluminium and aluminium alloys are major technological metals, offering desirable mechanical properties, low density, thermal and electrical conductivity. Importantly, they exhibit high recyclability. While these materials are relatively stable and corrosion-resistant in most environments, they are often subjected to corrosion and wear in harsh environments. Coatings are the most common method of corrosion protection of aluminium and its alloys. Coatings can improve not only corrosion resistance but also wear resistance, and can add functional properties to the surface. In the present review, the coatings are summarised in five groups: (1) barrier aluminium oxide coatings, including anodised coatings, plasma electrolytic oxidised coatings, coatings deposited by atomic layer deposition, and by hydrothermal treatment, (2) conversion coatings including zirconium, titanium, trivalent chromium, and phosphate (3) metallic coatings comprising clad and electroplated metal coatings, (4) organic coatings comprising powder and liquids organic coatings, and sol-gel coatings, and (5) inhibition and wettability control coatings, comprising coatings incorporating inhibitors or nanoparticles and superhydrophobic coatings. The review focuses on production methodologies and the physical-chemical characteristics of coatings. Advantages and potential shortcomings of individual coatings are discussed in terms of their use and corrosion protection.