The Effect of Heat Treatment Parameters on the Anodic Polarization Behavior of 440C Stainless Steel

The consequences of varying the heat treatment conditions for hardening 440C stainless steel on the anodic polarization behavior in dilute sulfuric acid were investigated by electrochemical methods. All measures of the quality of the metal for service in the passive state, i.e., corrosion resistance, such as critical current for passivation, minimum passive current density and passive range, changed similarly with changes in the heat treatment. The corrosion resistance was increased by raising the austenitizing temperature through the range 900 to 1100 C. The corrosion resistance was decreased when the quenching rate from the austenitizing temperature was lowered. To retain the benefits of a high austenitizing temperature, quenching rates faster than 30 C/s were required. The corrosion resistance was not affected by 4 hour tempering treatments up to 200 C, though tempering at higher temperatures caused progressive deterioration. Increasing the time and potential (up to 1.0 V_S.C.E.) of electrochemical passivation treatments improved the corrosion resistance but could not compensate for poor heat treatment.