Localized corrosion in selective laser melted SS316L in CO2 and H2S brines at elevated temperatures

Deeparekha Narayanan; Alan Martinez; Ulises Martin; Bilal Mansoor; Raymundo Case; Homero Castaneda

doi:10.1038/s41529-024-00468-4

Localized corrosion in selective laser melted SS316L in CO₂ and H₂S brines at elevated temperatures

Npj Mater Degrad. 2024;8(1):50. doi: 10.1038/s41529-024-00468-4. Epub 2024 May 10.

Authors

Deeparekha Narayanan^#¹, Alan Martinez^#¹, Ulises Martin¹, Bilal Mansoor², Raymundo Case¹, Homero Castaneda¹

Affiliations

¹ Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843 USA.
² Texas A&M University at Qatar, Doha, Qatar.

^# Contributed equally.

Abstract

In this work, the passivation and localized corrosion of selective laser melted (SLM) stainless steel 316 L when exposed to high pressures of CO₂ with the presence of H₂S and Cl^- at 25 °C and 125 °C were studied. Depletion of Cr/Mo was observed at the cell interiors and melt-pool boundaries (MPBs) compared to the cell boundaries. Volta potential differences obtained from scanning Kelvin probe force microscopy (SKPFM) showed that the MPBs were 8-20 mV lower than the matrix, while the cell interiors were 20-50 mV lower than the cell boundaries. Electrochemical impedance spectroscopy (EIS) and Mott-Schottky tests indicated a more defective passive film at 125 °C, and X-ray photoelectron spectroscopy (XPS) confirmed the formation of a less protective film with an increased S/O ratio at 125 °C than 25 °C. Initiation of localized corrosion was observed at the MPBs and pits formed after a week of immersion were wider by an order of magnitude at 125 °C than 25 °C, with evidence of cell-interior dissolution. While passivity was observed even at elevated temperatures, local chemical heterogeneities compromised the stability of the film and contributed to localized corrosion in SLM SS316L.

Keywords: Corrosion; Metals and alloys.