Abstract: Rubber compositions excellent in adhesion to metals, particularly suitable for steel cord coating rubbers, having a high vulcanizing rate and little offensive smell in an unvulcanized state, which comprise 100 parts by weight of a rubber and 0.01-1 part by weight as a cobalt element content of at least one cobalt oxyketone complex represented by the following general formula: ##STR1## wherein R.sub.5 -R.sub.14 are same or different, hydrogen atom, C.sub.1 -C.sub.18 alkyl, C.sub.5 -C.sub.12 cycloalkyl, C.sub.6 -C.sub.14 aryl, C.sub.6 -C.sub.14 aryl-C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.18 alkoxyl, C.sub.5 -C.sub.12 cycloalkoxyl, C.sub.6 -C.sub.14 aryloxyl, C.sub.6 -C.sub.14 aryl-C.sub.1 -C.sub.4 alkoxyl groups, or C.sub.2 -C.sub.18 hydrocarbon groups having at least one double bond.

Abstract: Rubber compositions excellent in adhesion to metals, particularly suitable for steel cord coating rubbers, having a high vulcanizing rate and little offensive smell in an unvulcanized state, which comprise 100 parts by weight of a rubber and 0.01.about.1 part by weight as a cobalt element content of at least one cobalt oxyketone complex represented by the following general formula: ##STR1## wherein R.sub.1 .about.R.sub.4 are same or different C.sub.1.about.18 alkyl, C.sub.5.about.12 cycloalkyl, C.sub.6.about.14 aryl-C.sub.1.about.4 alkyl, C.sub.1.about.18 alkoxyl, C.sub.5.about.12 cycloalkoxyl, C.sub.6.about.14 aryloxyl, C.sub.6.about.14 aryl-C.sub.1.about.4 alkoxyl groups, or C.sub.2.about.18 hydrocarbon groups having at least one double bond.