Effect of Heat Treatment on Corrosion Performance of Duplex Steel COR 25

The effect of heat treatment on the corrosionperformance of austenitic-ferritic duplex stain-less steel COR 25 in aqueous solution containing60%H_3PO_4+4%H_2SO_4+1500 ppm Cl~- at 95℃ was in-vestigated.When the solution temperature wasincreased from 950℃ to 1230℃,the corrosionresistance increased by two orders of magnitude,as shown by electrochemical measurements,im-mersion tests and direct observation under thescanning electron microscope.The specimensheat treated at solution temperatures of 950℃and 1030℃ were severely corroded along thephase boundaries;specimens treated at 113C℃and 1230℃ tended to selective corrosion causedby the dissimilar chromium contents of the aus-tenite and ferrite phases after heat treatment.