Investigation of Thiosulfate Adsorption on 316 Stainless Steel in Neutral Solutions by Radioactive Labeling, Electrochemistry, and Auger Electron Spectroscopy

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Abstract
Laser surface cladding (LSC) process was used to introduce high chromium‐nitrogen alloys on carbon steel to improve its corrosion resistance. The chemical composition, the resulting microstructure, and the electrochemical behavior in connection with the chemical composition of the surfaces of the cladded layers were analyzed in this study. Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) measurements were performed to evaluate the corrosion resistance of the cladded layers in deaerated solution at pH 4. The surfaces of the samples after EIS measurements were characterized with Auger electron spectroscopy and x‐ray photoelectron spectroscopy. The results showed that the Cr content as high as while the nitrogen concentration as high as were found in the cladded layer. Approximately of Si in all the LSC layers were also detected. The passive film resistance increased and the passive current density decreased with increasing the chromium‐nitrogen content in the cladded layer. Electrolyte analyses after EIS measurements showed that nitrogen atoms in the surface of LSC layer can be electrochemically reduced to . The surface of samples, after EIS measurements, consisted of chromium oxide, chromium nitride; ammonia and silicon oxide were found. The passive films resistance of LSC alloys might partially be attributed to the formation and adsorption of ammonia on the surfaces. The chromium nitride, silicon oxide incorporated with chromium oxide could possible modify the passive film and cause an improvement in corrosion resistance.

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