ROLE OF SURFACE COMPOSITION ON THE CORROSION RESISTANCE OF ELECTROPOLISHED 316L STAINLESS STEEL

摘要

Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS or ESCA) are used to determine the maximum Cr/Fe and the approximate depth of the oxide layer of AISI 316L components used for high purity gas distribution. It has been assumed that in electropolished 316L, corrosion resistance will increase as Cr/Fe and oxide thickness increase. However, this assumption ignores the effect of base chemistry. A study was designed to determine the relationship between surface composition, base chemistry, and corrosion resistance. Tests were performed on twenty-one heats of commercially available 316L electropolished tubing. The results of electrochemical pitting corrosion tests and general corrosion tests indicated no appreciable correlation between corrosion resistance and Cr/Fe ratio or oxide thickness. The best correlations from the surface science data suggest that thinner oxide layers and shallower depths of enrichment are associated with better corrosion resistance. However, a strong correlation was found between corrosion resistance and base chemistry of the tubing.