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。为此，本研究通过多种电化学测试手段，探究了ASTM A890/A 890M GR 5A超级双相不锈钢（SDSS）在60000ppm氯化钠水溶液中的腐蚀行为。所有试样均在475℃下分别时效2、10、50及100小时。动电位极化测试结果表明：当腐蚀电位进入钝化状态时，在相对于Ag/AgCl参比电极约400mV处会出现峰值电流，该峰值电流对钝化膜稳定性具有显著影响。峰值电流值随时效时长的增加而升高，其中时效100小时的试样峰值电流最高。为评估试样/钝化膜/电解液体系的行为及其在钝化区间内的变化，本研究从极化曲线中选取了三个电位点。结果显示，钝化膜的稳定性随时效时长的增加而劣化。此外，本研究还通过维氏显微硬度测试，将腐蚀测试结果与钢材的力学性能演化进行了对比。