Although the transition metals are less electropositive than alkali and alkaline earth metals, their standard reduction potentials seem to indicate that all of them expect copper should react with strong acids such as hydroelectric acid to produce hydrogen gas. However, most transition metals are inert toward acids or react slowly because of a protective layer of oxide. A case in point is chromium Despite its rather negative standard reduction potential, it is quite inert chemically because of the formation on its surfaces of chromium3 oxide. Cr2O3. Consequently, chromium is commonly used as a protective and noncorrosive plating on other metals. On automobile bumpers and trim, chromium plating serves a decorative as well as a functional purpose