Influence of inhibitors on the corrosion behavior of the X5CrNi18 10 stainless steel‐welded joint

• Published in: Materials and corrosion 2021-04, Vol.72 (4), p.694-707
• Main Authors: Radojković, Bojana, Kovačina, Jovanka, Jegdić, Bore, Bobić, Biljana, Alić, Behar, Marunkić, Dunja, Simović, Anđela
• Format: Article
• Language: English
• Subjects: Austenitic stainless steels; Base metal; Cerium nitrate; Corrosion inhibitors; Corrosion potential; Corrosion resistance; Corrosion tests; Electrochemical impedance spectroscopy; electrochemical methods; Heat affected zone; Intergranular corrosion; pitting corrosion; Pitting potential; Sodium nitrates; Stability analysis; Stainless steel; Uniform attack (corrosion); Weld metal; welded joint; Welded joints
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.202012039

This study considers the corrosion behavior of the X5CrNi18 10 stainless steel‐welded joint in NaCl solution, with and without the presence of several corrosion inhibitors (NaNO3, Ce(NO3)3, and CeCl3). The degree of sensitization of the welded joint to intergranular corrosion is determined using the electrochemical potentiokinetic reactivation method with a double‐loop method. Pitting corrosion tests are performed by the potentiodynamic method. Resistance to general corrosion and the stability of the passive film is assessed based on the results of electrochemical impedance spectroscopy measurements, as well as on the values of the corrosion and passivation current. The main goal of this study is to determine the relation of the welded joint microstructure to general and pitting corrosion in the presence of the corrosion inhibitors. The value of pitting potential for the base metal and weld metal in the presence of the NaNO3 or Ce(NO3)3 inhibitor is shifted to potentials in the transpassive area. The pitting potential for the heat‐affected zone also possesses a noticeable higher value. However, nitrate ions do not increase the general corrosion resistance of any part of the welded joint. CeCl3 does not increase resistance to general or pitting corrosion. The relation between the microstructure of the welded joint and its corrosion resistance in the presence of inhibitors was investigated. The resistance to pitting corrosion of the base metal and weld metal in NaCl + NaNO3 and NaCl + Ce(NO3)3 is complete, whereas the heat‐affected zone (HAZ) shows a much lesser level of protection. However, nitrate ions do not increase general corrosion resistance in either HAZ, weld metal, or base metal. CeCl3 does not increase either resistance to general or pitting corrosion.