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Stainless steel and stainless steel clad aluminum (bimetal) have been used for bright exterior trim for many years. The need to manufacture bright or colored trim with the same tools has led to the development of various coating systems to color stainless steel or bimetal trim. This paper describes the mechanisms of coatings disbondment that can occur on trim. Accelerated tests for determining disbondment resistance are described and the results from these tests for a wide range of coatings are presented. Coating systems that are acceptable for stainless steel and stainless steel clad aluminum are identified.

In order to confirm the behavior of various bumper materials, Texas Instruments conducted a performance field survey of existing bumpers in service. A large fleet of trucks equipped with stainless steel clad aluminum bumpers was identified in order to maximize the data obtained on this material system. The fleet owned and operated by E. W. Wiley Co., Fargo, North Dakota was chosen because of the large number of accessible bumpers in service, the severity of the location and the extensive service of trucks in that fleet. Bumper system included in the survey were stainless steel clad aluminum, chrome plated steel and chrome plated aluminum.

A number of factors are considered important when considering the choice of material for light vehicle bumpers. These include economics, styling, appearance, fabricability, and durability. Additional factors are introduced due to safety, fuel efficiency and environmental issues. As these issues become more stringent, the choice of material becomes more difficult because traditional materials are not able to provide all of the required properties. This paper describes clad materials systems which provide the required properties while introducing weight reduction in bumpers. Specific combinations of stainless steel and aluminum in a clad configuration have been used on automobiles and trucks for many years in a wide range of applications. These clad metal systems have all of the desirable properties of the individual components and provide a light weight alternative to the limitations of traditional materials.

Transition materials consisting of steel clad aluminum have been used to join aluminum and steel. This technique allows joining by resistance spot welding since the clad transition material allows the actual transition from one metal to the other to occur at the clad bond interface. Welding studies show that in the recommended range of weld parameters, high strength joints are produced. A wide range of corrosion tests have been used to determine the durability of these joints in automotive environments. Results show that the use of transition material in joining aluminum to steel or EG steel eliminates galvanic corrosion.

Previous work has shown that mirror bright stainless steel clad to lightweight aluminum offers an optimum combination of weight, appearance, fabricability, styling, and durability against road damage and corrosion for automotive trim and bumper applications. This paper characterizes the properties of stainless steel-aluminum clad bumper materials for application on Class 8 trucks. The rule of mixtures is confirmed for an SAE 30301 stainless steel clad to 3003 aluminum, and is applied to show the tradeoffs between weight, strength, and cost that affect material selection for truck bumpers. The fabricability is demonstrated by sweeping, aerodynamic bumper designs that are readily formed, and is quantified by forming limit diagrams of 301SS / 3003Al clad and 301 stainless steel. The durability against road damage is demonstrated with Gravelometer testing, followed by ASTM standardized corrosion testing. The clad is also resistant to erosion from water impingement.