Formation of protective anodic oxides on aluminium by low voltage anodising in sulphuric acid with cerium nitrate and tartaric acid additions

The effects of the anodising potential and of the combined addition of tartaric acid and cerium nitrate to a sulphuric acid anodising bath on the corrosion behaviour of high purity aluminium and on AA2024T3 aerospace aluminium alloy have been systematically investigated. It is found that the anodising potential is critical in determining the anticorrosion performance; lower potential generates finer pores that provide enhanced corrosion protection compared with the larger pores generated at higher potentials. At both anodising potentials, the addition of cerium nitrate alone to the sulphuric acid bath does not increase significantly the anticorrosion performance. Conversely, the addition of tartaric acid alone is generally beneficial. Finally, when cerium nitrate is added in combination with tartaric acid a further improvement of the corrosion resistance is observed.