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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.

Process consistency and long electrode-life are essential requirements for users of resistance spot welding (RSW) in the automotive industry. RSW is the dominant joining process for manufacturing automotive body structures from sheet materials. The technique is cost effective (particularly in high-volume production), makes joints rapidly, is easy to automate, and it has no per-joint consumables. These beneficial attributes apply equally to RSW of aluminium automotive structures. However, there has been some reluctance in the industry to embrace spot welding for aluminium. This is because the electrode-life is much shorter than that experienced when welding traditional uncoated, plain-carbon steels, and there is a general lack of confidence in the consistency of the process. This paper describes a potentially non-intrusive method that addresses these concerns.

An A356T61 cast aluminum lower suspension control arm has been put into production for the Lincoln Mark VIII. The mechanical requirements which drive the design for a critical part like this are discussed, together with some of the background knowledge needed to address the issues surrounding alloy and process selection. Particularly as it must be realized that the process impacts the degree to which the potential of the alloy can be realized. With this in mind, some of the research activities which have been spawned in parallel with the production activities are briefly covered. The sequence of events involved in the design and prototyping of the part itself are outlined, as is the implementation of a specialized low pressure casting line to produce the part. Part performance to date has been excellent and the quality controls and test methods which have been put in place to see that this remains so are also covered.

The need to reduce or contain a weight increase in new automobile designs is leading to the use of more and more aluminum and, in particular, to the adoption of aluminum outer body panels in a number of volume production vehicles. This has been made possible by improvements in the properties of heat treatable aluminum sheet materials and also from a better understanding of the issues related to part design and manufacturing. The alloy AA6111 has become the material of choice due to its unique combination of formability and paint bake strengthening and is used, for example, in the deck lids of the current Ford Crown Victoria, Grand Marquis and Taurus/Sable models. A modified process for this alloy has now been developed which significantly increases its paint bake strengthening and can be used either to obtain even better dent resistance or to reduce the gauge and hence obtain cost and weight savings.

Weld bonding of aluminium autobody structures offers automotive vehicle manufacturers the opportunity of achieving significant weight reduction, compared to equivalent steel structures. Further, this is achievable using volume production manufacturing methods. This paper considers all key aspects of the weld bonding process, in particular the equipment requirements and the factors that are important in reliably achieving satisfactory structures. Methods of minimising damage to the adhesive bondline and assessment of spot weld quality are discussed. Using experience gained from extensive weld bonding trials, suitable parameters for robust weld bonding are recommended.

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.

Efforts towards weight reduction are leading towards increasing use of aluminum components on automobiles. Although aluminum on its own has inherently superior corrosion resistance to steel, galvanic action between the aluminum and steel or galvanized parts can lead to severe corrosion. Straightforward and effective methods of preventing galvanic corrosion from the subject of this paper. Since many aluminum components are connected to steel structures by mechanical fasteners, protective coatings on fasteners were evaluated as well. Galvanic test couples were prepared in a manner simulating typical automotive assembly conditions while incorporating features which would lead to enhanced corrosion. A variety of chemical treatments and coatings on the fasteners as well as barriers between the dissimilar metals were evaluated for corrosion prevention between the aluminum and cold rolled or galvanized steel. Comparison between neutral salt spray and cyclic corrosion tests is provided.