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The movement towards extended warranties in the automobile industry has focussed attention on corrosion performance of many components, particularly cast aluminum wheels. Filiform corrosion is of particular concern since it can severely affect the appearance of the wheel. The appearance and the choice of wheel design are the most attractive features to customers. In order to enhance the filiform corrosion resistance of cast aluminum wheels, cleaning, pretreatment, coating and alloy parameters are critical and need to be optimized. In this paper, the effects of alloy composition and condition on filiform corrosion are reviewed. A series of cast discs were prepared with variations in iron, zinc and copper levels around the standard A356.2 alloy composition. Apart from composition, certain specimens were subjected to different heat treatment and ageing conditions. The effects of porosity and different machining procedures were also evaluated.

The rapid increase over the past few years in the use of aluminum closure panels on vehicles is anticipated to continue well into the next decade. Along with this increased usage comes the need for a greater amount of cosmetic repair of these closures in after market body shops. Although paint repair systems for aluminum have been available for some time, their effectiveness on newer alloys needed to be demonstrated. Some work in the recent literature has also questioned the corrosion and paint performance of aluminum closures after sanding. In this study, extensive surface analysis of AA6111 closure sheet material was carried out in the as-received condition, after phosphating and after sanding, cleaning and pretreating with selected paint repair systems from major automotive paint suppliers to determine the effects of surface residues or contaminants on subsequent corrosion performance.