Pitting studies were conducted on a commercial Type 316L (UNS S31603) stainless steel (COM 316L) and a Type 316L steel refined by electron beam cold hearth remelting (EBCHR) to decrease the inclusion content. The steels were subjected to potentiodynamic polarization pitting tests in 0.6 M sodium bromide (NaBr) and 0.6 M sodium chloride (NaCl) solutions. Pitting morphologies and distributions were examined by scanning electron microscopy. The EBCHR steel (EBCHR 316L) exhibited a much lower pitting density than COM 316L, with no significant improvement in pitting potential, in both halide solutions. Also, the fewer pits on EBCHR 316L were generally larger and/or more open than on COM 316L, causing the overall beneficial effects of EBCHR refining on pitting to be questionable. The bromide solution tended to produce a lower mean pitting potential than chloride for each steel condition and produced larger numbers of small crystallographic pits on COM 316L. Pitting sites and adsorption of halide ions are discussed.

Subject
Pits, Halides, Sodium chloride, Iron, Density, Sodium chloride solution, Steel, Pitting, Bromide, Stainless steel, Polarization, Chlorides, Inclusions
Keywords:
bromide, chloride, ion adsorption, pit initiation, pitting density, pitting potential
NACE International
2001
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