THE EFFECT OF SURFACE TREATMENT ON THE CORROSION BEHAVIOUR OF A HIGH STRENGTH ALUMINIUM ALLOY

摘要

The effect of surface cleaning on the corrosion resistance of the high strength aerospace aluminium alloy 2024-T351 was investigated. Addition of cerium chloride to the nitric acid desmut solution was found to improve the corrosion resistance of the surface by removing the cathodically-active S-phase (Al_2CuMg) intermetallic particles. This decreases the rate of the cathodic reaction, lowering the open circuit potential, and decreasing the current available to support growing pits. It was determined that the chloride ions rather than the cerium ions were critical in promoting dissolution of S-phase. This is probably associated with complexing of the copper component of the particles by chloride, and promoting surface mobility of copper on the surface, which allows particle dissolution to proceed rapidly.