5. Analysis and Evaluation

The knowledge on steel corrosion, galvanic corrosion of dissimilar materials, hydrogen embrittlement of steel, and nondestructive testing techniques in automobiles is summarized, and an overview of the issues and research results related to them in this project is given. Chemical and physical stresses during vehicle use cause various degradations. In particular, corrosion and hydrogen embrittlement are difficult to evaluate. The outlines of the developments on this project including electrochemical measurement techniques on the surfaces of microstructures of 1.5 GPa high strength steel containing high carbon, galvanic corrosion of multi-material automobile bodies, standard test methods for evaluating hydrogen embrittlement, and analysis techniques for crack propagation morphology were presented. Nondestructive testing is positioned to eliminate defective products in the process and to estimate the remaining life of the product. In the production process, it is desirable to be able to eliminate defective products online or in-line without affecting the product, and it is necessary to introduce equipment that can identify defective parts nondestructively without relying on human labor. In addition, to estimate the remaining life expectancy, studies to correlate various measurements with life expectancy are needed, and it is expected that many producers will cooperate in this research in many cases.