Abstract: A method for protecting the surface of a metal surface which comprises applying to said surface an organophosphorus compound of the formula ##STR1## wherein A IS 0 OR 1R is a branched or unbranched chained bivalent alkylene radical of 1 to 12 carbon atoms which is substituted or unsubstituted and can contain in the chain structure --O--, --S--, ##STR2## R' is a branched or unbranched alkyl radical of 1 to 12 carbon atoms which can be halogen substituted and can contain in the chain structure ##STR3## X is an epoxy ring, halogen, alkylene, carboxylic acid ester residue, amino, isocyanato, isothiocyanato, urea, thiourea, urethano, alkyl substituted thio radical or the radical or a heterocyclic ring containing O, S, or N in the ring structure; a new organophosphorus compounds having the formula set forth above and more particularly defined by specific chemical structures.