Enhancing resistance to pitting corrosion in mechanically polished stainless steel 316 LVM by water treatment

We present an extremely simple and environmentally friendly technique that appears to dramatically reduce pitting corrosion on stainless steel 316LVM. Mechanically polished SS 316LVM wire samples were treated in 90 °C high purity deionized water for different durations, then tested for pitting corrosion using potentiodynamic, potentiostatic as well as in situ imaging techniques. Wires treated for 2 or 3 h showed the greatest enhancement of pitting resistance when tested in 0.9% (by mass) NaCl solutions. To investigate the most plausible cause for the increased corrosion resistance, preliminary scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) tests were performed on SS AISI 316L disks. We identified micron sized MnS inclusions on the polished disk surfaces. After treatments in heated high purity deionized water, SEM revealed micropits and EDS did not detect sulfur where MnS previously existed.

► Freshly polished stainless steel wires were treated in 90 °C deionized water.
► The pitting corrosion resistance in 0.9% (mass) NaCl increased for treated wires.
► SEM/EDS investigations showed typical MnS inclusions before water treatments.
► SEM/EDS showed sulfur-free pits after the water treatments.
► Dissolution of the exposed inclusions may cause the increased pitting resistance.