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The Auto/Steel Partnership established the Light Truck Frame Project Group in 1996 with two objectives: (a) to develop materials, design and fabrication knowledge that would enable the frames on North American OEM (original equipment manufacturer) light trucks to be reduced in weight, and (b) to improve corrosion resistance of frames on these vehicles, thereby allowing a reduction in the thickness of the components and a reduction in frame weight. To address the issues relating to corrosion, a subgroup of the Light Truck Frame Project Group was formed. The group comprised representatives from the North American automotive companies, test laboratories, frame manufacturers, and steel producers. As part of a comprehensive test program, the Corrosion Subgroup has completed tests on frame coatings. Using coated panels of a low carbon hot rolled and pickled steel sheet and two types of accelerated cyclic corrosion tests, seven frame coatings were tested for corrosion performance.

Since 1985, the Body Division of the Automotive Corrosion and Prevention Committee of SAE (ACAP) has conducted biannual surveys of automotive body corrosion in the Detroit area. The purpose of these surveys is to track industry wide corrosion protection improvements and to make this information available for public consumption. The survey consists of a closed car parking lot survey checking for perforations, blisters, and surface rust. This paper reports the results of the five surveys conducted to date.

Galvannealed sheet steel is gaining acceptance by automotive manufacturers due to its combination of properties and cost. Galvanneal can be produced by several processes including the most common method termed the “hot” line hot dip coating process, but also using “flux” line hot dip coating application. Similarly, several types of phosphate coatings: Zn, Zn-Ni, and Zn-Ni-Mn phosphates can be applied to these materials prior to painting to enhance paint adhesion and painted corrosion resistance. This manuscript reports the affects of commercial phosphate type and galvanneal type (based on production method and properties) on the corrosion performance of galvanneal. In addition, painted corrosion performance of galvanneal is compared to painted corrosion performance of electroplated zinc. The manuscript also describes the use of electrochemical methods as one alternative to conventional test methods resulting in substantial time savings.

Corrosion resistance has been the major impetus toward increased use of galvanneal and other coated sheet products by the automotive industry. Galvanneal has the additional advantages of good weldability, due to the iron in the coating, and a higher surface porosity which leads to better paint adhesion. The porosity of the galvanneal surface, however, could also lead to reduced cleanability. This paper reports the effects of pretreatment variables on galvanneal phosphatability and resulting painted corrosion performance. The studies showed that the rust preventative oil applied and the alkaline cleaner used to clean samples prior to phosphating had significant effects on carbon residuals after cleaning. The painted corrosion performance of galvanneal panels with various levels of residual carbon showed a much smaller effect within a given cyclic test. The studies also indicated significant differences in performance depending on the type of cyclic test performed.

A program was initiated to determine corrosion performance of coated sheet products. The program examined the performance of galvannealed, hot-dip galvanized and electroplated zinc coated steel sheet in a variety of cyclic laboratory corrosion tests. Both perforation and cosmetic corrosion susceptibility were evaluated. Materials were pretreated using immersion and spray phosphate systems and were also prepared without a phosphate pretreatment. Results of these studies will be presented in this paper.

Automotive demands for increased service life and use of flexible fuel blends of alcohol and gasoline have propelled the development of new materials for automotive fuel systems. Traditional fuel system materials, i.e., bare or prepainted terne coated steel sheet, which do not meet the new requirements are being replaced with prepainted zinc-nickel coated steel sheet. Automotive fuel tanks and fuel system components made from the new prepainted zinc-nickel steel sheet offer increased service life and compatibility with the entire range of flexible fuel blends. This paper describes the results of several laboratory corrosion studies which examined the environmental corrosion performance and the fuel compatibility of prepainted zinc-nickel coated steel as a function of several system properties. Performance is compared to prepainted terne, prepainted hot dip tin, and prepainted galvanneal.