The improved stability and corrosion resistance of the passive film on Mn-containing FeCrNiCoMnx high entropy alloys by multiple pickling

• Published in: Journal of alloys and compounds Vol. 962; p. 171141
• Main Authors: Hsu, Kuo-Min, Chien, Wei-Liang, Lin, Chao-Sung
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.11.2023
• Subjects: Corrosion; High entropy alloys; Microstructure; Surface and interface; X-ray photoelectron spectroscopy; High entropy alloys; Corrosion; Microstructure; X-ray photoelectron spectroscopy; Surface and interface
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.171141

This study detailed the effect of the various inclusions in FeCrNiCoMnx high entropy alloys on the corrosion behavior in 0.5 M sulfuric acid. MnCrAlO4, MnCr2O4, MnO, and MnS inclusions, which constituted different complex structures, were found in Mn-containing FeCrNiCoMnx while only Cr2O3 existed in FeCrNiCo. The presence of MnS was found to deteriorate the stability of the passive film on Mn-containing FeCrNiCoMnx when anodically polarized in 0.5 M H2SO4. Therefore, a multiple-pickling process according to ASTM A380M-17 was first applied and successfully improved the stability and corrosion resistance of the passive film. Nevertheless, the degree of improvement in the corrosion resistance decreased with less Mn content. This results from more [Cr(H2O)6]F3 in the passive film with less MnO2, which served a role in mitigating the attack of HF on Cr2O3 during pickling. For the immersion tests, the pickled FeCrNiCo suffered preferential dissolution in Fe and Cr at the beginning of immersion in 0.5 M H2SO4 and thus exhibited a surface more susceptible to corrosion after the 7 and 14 days of immersion compared to FeCrNiCoMn0.3. •Evaluate the stability of the passive film on Mn-containing FeCrNiCoMnx.•Detail the effect of various inclusions on the corrosion behavior.•Multiple pickling of FeCrNiCoMnx in HNO3 + HF followed by in HNO3.•Multiple pickling improves the stability and anticorrosion of passive film.•Mn oxide in the passive film mitigates the attack in HF + HNO3.