Disclosed is a quenching medium for treating a heated metal part, said medium comprising water and a polyacrylate terpolymer comprising acrylamide and/or methacrylamide monomer units, acrylic acid and/or methacrylic acid monomer units and alkyl alkoxylate allyl ether monomer units where the acid groups are in the form of an alkali metal salt and where the alkyl alkoxylate allyl ether monomers are of the formula where n is an integer from 1 to about 30, R is ethylene, propylene or butylene and G is an alkyl group of 8 to 30 carbon atoms. Also disclosed is a method for quenching a heated metal part, which process comprises immersing said metal part in the quenching medium. Also disclosed are the polyacrylate ternary copolymers.