Abstract: The effect of heat treatment on the corrosion performance of austenitic-ferritic duplex stain- less steel COR 25 in aqueous solution containing 60%H_3PO_4+4%H_2SO_4+1500 ppm Cl~- at 95℃ was in- vestigated.When the solution temperature was increased from 950℃ to 1230℃,the corrosion resistance increased by two orders of magnitude, as shown by electrochemical measurements,im- mersion tests and direct observation under the scanning electron microscope.The specimens heat treated at solution temperatures of 950℃ and 1030℃ were severely corroded along the phase boundaries;specimens treated at 113C℃ and 1230℃ tended to selective corrosion caused by the dissimilar chromium contents of the aus- tenite and ferrite phases after heat treatment.

Key words: heat treatment, duplex stainless steel, electrochemical behavior, corrosion