Sulfo-tartaric anodizing

aluminumfor aeronauticslarge series

Sulpho-tartaric anodic oxidation is the emanation of an Alenia patent improved by Airbus. The aim is to replace chromic anodic oxidation, (CAO). It is generally performed in a bath containing about 40 g/l of sulphuric acid and 80g/l of tartaric acid, at a temperature of 35 to 40°C. The constant voltage is 14/15V. The cycles of approximately 25 minutes include a voltage rise of 5 minutes and then a steady state of 20 to 25 minutes. The sulpho-tartaric anodizing forms very thin layers, 2 to 7 µm (thicknesses similar to those formed during a CAO). It creates good corrosion resistance thanks to the adhesion of the paint films, painting is performed on an unsealed layer. Its influence on the fatigue characteristics is moderate (reduction in the order of 20 to 30% compared to the bare substrate, similar to that induced by a CAO). Appearance: colourless to slightly iridescent Thickness: 2 to 7 µm Surface condition: slight degradation of the roughness Reduction in fatigue: comparable to that of the CAO, depending on the alloy, may be compensated for by prior shot peening