Shares plunged 22 percent and the cost to insure Kobe Steel debt against default soared as customers including Toyota, Honda and Subaru said they had used materials that were subject to falsification

Kyoto University is working with a number of Japanese carmakers, auto part and electronics makers—as well as foreign companies—on the research.

As aluminum becomes more popular in vehicles, the industry is searching for safer ways to join mixed materials. There are several academic studies related to the lightweighting issue, including one from Ohio State University, which is studying “civilized explosive welding” as a way to join dissimilar materials and avoid corrosion.