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The inherent corrosion resistance of aluminum is much greater than automotive steels. To demonstrate this principle in a fashion acceptable to the automotive industry, a test program was run which incorporated lab, test track and real life trials on both unpainted and painted aluminum and painted steel. The lab program consisted of neutral salt and cyclic corrosion tests. Having demonstrated that aluminum does not need electrocoating for good corrosion integrity, alternatives to electrocoating which would allow primers to be applied only where necessary for esthetic purposes were sought. Several primers were selected for study based upon current automotive usage. Factors such as the degree of pretreatment prior to primer application and the presence of residual lubricant on the metal were evaluated.

Previous work has shown that variations in wheel alloy chemistry, particularly with respect to copper and iron levels, can have a pronounced effect on filiform corrosion performance. In this study, an examination of A356.2 alloy chemistry variants and their effects on corrosion was carried out in greater detail. The emphasis was on copper and iron variants, both alone and in combination. Copper levels ranged from 0.005 to 0.22% and iron from 0.04 to 0.23%. The effect of manganese additions was also examined, with levels ranging from 0.002 to 0.07%. In addition to the alloying variants, the level of dispersed oxides in the castings was varied to determine any effects on corrosion performance. Although filiform corrosion performance of painted samples was the primary focus of this study, the corrosion behaviour of unpainted samples was also evaluated for comparison purposes.

The recycling and reclamation of metal-matrix composites (MMC's) are critical aspects of the commercialization process. By recycling, we mean the economic processing of MMC scrap for reuse as composite. Reclamation refers to the separation and recovery of the individual components of the composite, i.e., the various aluminum alloys and ceramic particles. Three forms of MMC wrought alloy scrap have been considered; i.e., D. C. (direct chill) cast log ends, extrusion butts, and cut extrusion scrap. Recycling each of these forms of scrap back into D. C. cast extrusion billet has been demonstrated. This has been accomplished by recycling the scrap back through the basic mixing process. Various ratios of scrap to virgin composite have been explored and optimum blends are being studied. Similarly, for MMC foundry alloy (high silicon) gates and risers produced in shape-casting, fluxing and degassing techniques have been developed so these may be recycled back into useful castings.

The feasibility of applying laser induced optical emission spectroscopy to the high speed sorting of mixed-alloy aluminum scrap from automobiles has been established. The basic spectroscopy for analysing aluminum alloys for the major alloying elements is reviewed and key technical issues solved in developing the total sorting system are highlighted. Opportunities to apply this technology to the recycling of scrapped automobiles are discussed.

This paper will describe the main features of two newly-developed enabling technologies for the future establishment of an integrated system to recover the full value of the aluminum from scrapped aluminum intensive vehicles. These technologies are fluidized bed decoating and alloy sorting using analysis by laser induced optical emission spectroscopy. Aluminum Intensive Vehicles will employ substantial quantities of sheet material, most of which will have fairly heavy paint coatings and possibly adhesives. While it may be possible to remove and segregate some of the closure panels and the major aluminum castings, the main body structure will need to be shredded to facilitate both the separation of the various aluminum and other materials and also the subsequent thermal decoating of paint films and adhesives. The decoating is necessary to ensure complete pyrolysis of the coatings and to avoid the excessive dross losses encountered when as-painted scrap is remelted.