PRODUCTION OF CORROSION-PROOF SUSPENSION SPRING

PURPOSE:To provide the method for producing a corrosion-proof suspension spring where the occurrence of pitting corrosion to be the origin of the fracture of spring is prevented and also delayed fracture is prevented. CONSTITUTION:In a suspension spring producing method by means of a series of stages consisting of soaking, hot forming, hardening, tempering, shot peening, chemical conversion treatment, etc., or in a suspension spring manufacturing method by means of a series of stages consisting of cold forming, soaking, hardening, tempering, shot peening, chemical conversion treatment, etc., at least a part of the surface of a spring material, passed through a series of spring manufacturing stages and shot-peened, is electroplated with manganese. A heating treatment stage is separately provided, and a dense passivating film is formed on the plated surface and passed through a series of spring manufacturing stages and further, coating-free finish is performed. By this method, the occurrence of pitting corrosion to be the origin of corrosion fatigue and fracture in a salt damage environment can be prevented, and delayed fracture can also be prevented.