The effect of corrosion resistant non chromate surface treatments on the fatigue behaviour aluminium alloys

Aluminum alloys are widely used in the aircraft and marine industries due their good strength to weight ratio. However, surface treatment is required to protect them from corrosion. Traditionally, Chromate based conversion coatings are applied but these are environmentally unfriendly which has initiated research programs to find alternatives to replace them. For this study, the titanate ion was used as a replacement for the Chromate ion. Both mechanical and chemical treatments were applied to surfaces during the multistage conversion coating process. In this study, the effect of mechanical surface finishing and chemical conversion coating on fatigue life was investigated. A decrease in fatigue life from either process is undesirable. There was a decrease in fatigue life after mechanical treatment with abrasive media. However, the conversion coating process did not affect the fatigue life. Fatigue crack initiation is most likely to take place at Al-Cu-Mn intermetallics