Effect of Copper Addition on Pitting Corrosion of MA-Al

This paper is intended to highlight the effect of copper addition on the pitting corrosion resistance of aluminium-base powder metallurgy parts. Results obtained on these mechanically alloyed (MA) specimens are compared with parts of MA-Al without added copper, as well as with commercial aluminium alloys. Immersion tests from 2 to 96 hours in 3.5% NaCl solutions, and potentiostatic techniques, were used to study the pitting corrosion. It was concluded that copper addition, in a similar way that in commercial aluminium alloys, produces a negative effect on the pitting corrosion resistance, because of the formation of Al₂Cu. These precipitates produce galvanic cells that favour the specimen pit. Therefore, increasing the copper content of MA-Al, although improving their ductility, worsens the pitting corrosion resistance of these alloys