The purpose of the present invention is to provide a biocorrosion inhibitor for metals which is highly safe from the standpoint of environmental and occupational safety. The biocorrosion inhibitor for metals contains 1,9-nonanedial and/or 2-methyl-1,8-octanedial as the active ingredient.La presente invención apunta a proporcionar un agente para inhibir la biocorrosión de un metal, el cual muestra alta seguridad ambiental y ocupacional un agente para inhibir la biocorrosión de un metal, que comprende 1,9-nonanodial y/o 2-metil-1,8-octanodial como ingrediente activo.
