1996-02-01

Hydrogen Embrittlement in Automotive Fastener Applications 960312

Fastener failure due to hydrogen embrittlement is of significant concern in the automotive industry. These types of failures occur unexpectedly. They may be very costly to the automotive company and fastener supplier, not only monetarily, but also in terms of customer satisfaction and safety. This paper is an overview of a program which one automotive company initiated to minimize hydrogen embrittlement in fasteners. The objectives of the program were two-fold. One was to obtain a better understanding of the hydrogen embrittlement phenomena as it relates to automotive fastener materials and processes. The second and most important objective, was to eliminate hydrogen embrittlement failures in vehicles.
Early program efforts concentrated on a review of fastener applications and corrosion protection systems to optimize coated fasteners for hydrogen embrittlement resistance. A concurrent program led to the development of a new fastener specification directed at minimizing hydrogen introduction and hydrogen retention as a result of coating application. Specific controls were put on fastener lot validation testing, and on baking practices as a function of fastener hardness level, cleaning and coating processes.
Joint research programs were initiated within academia and the fastener industry to better understand the fundamentals of hydrogen embrittlement in fasteners. The research program concentrated on the effects of hydrogen adsorption during electrochemical processing, hydrogen evolution during baking as functions of fastener-material and coating-process variation, and new multi-phase cold-heading steels. It is thought that these new steels may be inherently less susceptible to hydrogen damage than other commonly used fastener steel grades.

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