A metal article is protected from corrosion under prolonged exposure to normal ambient atmospheric conditions which cause such corrosion by coating the metal article, optionally in the presence of an adherent organic resinous coating, which comprises treating the metal with an effective amount of effective amount of one or more hydrocarbyl-substituted sulfonyl amido diphenylamine compounds for the corrosion protection of the metal article. These compound(s) are of the formula p-(R--SO.sub.2 --NH--C.sub.6 H.sub.4 --NH)--C.sub.6 H.sub.5, where R is a substituted or unsubstituted hydrocarbyl group selected from the group consisting of alkyl, aryl, alkaryl, aralkyl, alkenyl, and cycloalkyl. A particularly preferred compound is p-(p-toluene sulfonyl amido)-diphenylamine.