Evaluation of Alloy 146, 279, 900, and 926 sensitization to intergranular corrosion by means of electrochemical methods and image analysis

• Published in: Corrosion science Vol. 51; no. 9; pp. 2080 - 2091
• Main Authors: Leiva-García, R., Muñoz-Portero, M.J., García-Antón, J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2009; Elsevier
• Subjects: A. Intermetallic; A. Stainless steel; Applied sciences; C. Intergranular corrosion; Corrosion; Corrosion environments; Exact sciences and technology; Metals. Metallurgy; C. Intergranular corrosion; A. Stainless steel; A. Intermetallic; Image analysis; Electrochemical method; Stainless steel; Intermetallic compound; A Stainless steel; Sensitization; Intergranular corrosion
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2009.05.036

Properties of stainless steels are affected by improper heat treatment. When that happens, the material can become sensitive to intergranular corrosion. This loss of properties is due to a microstructural changes. In this paper, electrochemical potentiokinetic reactivation tests ( single and double loop) were used to evaluate steel sensitization to intergranular corrosion. Four alloys, Alloy 146 (UNS 1.4331) and 279 (UNS 1.4429) (austenitic stainless steels), Alloy 900 (UNS 1.4462) (duplex stainless steel), and Alloy 926 (UNS N08926) (high alloyed stainless steel), were employed as working electrodes. The specimens were sensitized at different temperatures (600–825 °C) for periods of 1 or 2 h in argon atmosphere. Electrochemical tests were conducted using the electro-optical devices P-200002525 and P-200002526. These devices permit to obtain images of the electrode surface and electrochemical data simultaneously. In addition, these results were compared to standardized etching with oxalic acid (ASTM A-262), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). Two alloys showed sensitization to intergranular corrosion, Alloy 900 and Alloy 926 at 725 and 825 °C. Additionally, the single and double loop methods showed different passivation results. In the double loop test, the formation of a layer over the entire electrode surface was visible during the process of activation. The film remained until the end of experiment. However, in the single loop method no significant variations were observed on the electrode surface during passivation process, but if material is sensitized a film was formed during reactivation branch.