Heat Treatment Effects on ASTM A890/A 890M GR 5A Super Duplex Stainless Steel Passivity

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.

热处理可改变不锈钢的耐腐蚀性能。本研究采用多种电化学测试方法，针对ASTM A890/A 890M GR 5A超级双相不锈钢（super duplex stainless steels, SDSS）在60000 ppm氯化钠水溶液中的腐蚀行为展开了探究。试样于475℃下分别时效2、10、50与100小时。动电位极化测试结果显示，当腐蚀电位进入钝化状态时，在相对于Ag/AgCl参比电极约400 mV处可检测到峰值电流，该峰值电流对钝化膜稳定性影响显著。峰值电流值随时效时长的增加而升高，其中100小时时效试样的峰值电流最高。研究人员从极化曲线中选取三个电位，以评估试样/钝化膜/电解液体系的行为及其在钝化区间内的变化。结果表明，钝化膜的稳定性随时效时间延长而劣化。此外，本研究还将腐蚀测试结果与通过维氏显微硬度测试得到的钢材力学性能演变进行了对比分析。