Heat treatment effects on ASTM A890/A 890M GR 5A super duplex stainless steel passivity

Abstract

Heat treatment can modify the corrosion resistance of stainless steels. Thus, the corrosion behavior of ASTM A890/A 890M GR 5A super duplex stainless steels (SDSS) has been investigated in aqueous 60,000 ppm NaCl solution by several electrochemical tests. The specimens were aged for 2, 10, 50 and 100 hours at 475 ºC. Potentiodynamic polarization studies showed that, when the corrosion potential comes to the passivation state, a peak current is detected at about 400 mV vs. Ag/AgCl, with a strong influence on the film stability. The peak current value increased with the aging time; the highest peak value was for the sample aged for 100 h. Three potentials were chosen from the polarization curves in order to evaluate the sample/film/solution behavior and their changes over the passivation range. The results indicate that the passive film was degraded with the increase of the aging time. In addition, the results of the corrosion tests were compared with the evolution of the mechanical properties of the steels by the Vickers microhardness test.