The corrosion behaviors of stainless steel weldments in sodium chloride solution observed using a novel electrochemical measurement approach

Stainless steels like 316 stainless steel (SS316) and 2205 duplex stainless steel (SS2205) have been widely used in industries such as desalination because of their excellent general corrosion resistance. However the corrosion resistant characteristics of stainless steels may be adversely affected by welding process that could result in modifications of local composition and microstructures. It is therefore critical to assess and understand the corrosion behaviors of stainless steel weldments. In this work, a novel approach to carry out electrochemical measurements on selected welding zones was employed. Standard polarization tests were applied to the selected zones on stainless steel weldments exposed to sodium chloride solutions. Weldments of SS316 and SS2205 were chosen as examples to illustrate the application of this novel electrochemical measurement approach. The results showed that each zone on the stainless steel weldments exhibited different corrosion characteristics and the weldments of SS316 and SS2205 behaved differently. The results suggested that SS2205 weldment was less resistant to pitting corrosion than SS316 weldment, although SS2205 base metal had much better pitting corrosion resistance than SS316 base metal. The corrosion behavior of each of the zones was confirmed to be affected by the surface morphology, microstructure and surface composition.