Heavy oxides from welding on steel can serve as a film on the surface and indicate the Chromium/Iron underlying metals surface has been depleted of Chromium and can be a site for the initiation of corrosion mechanisms such as crevice corrosion and pitting.
The electropolishing process is designed to remove discoloration and a thin layer of material approximately 25-50 µm resulting in improved corrosion resistance of the metal achieving CCP ranges typically in the range of 450 mV when tested using cyclic polarization tests on samples welded with 50 ppm O2.
Tests have further shown when have been welded with 20 ppm O2 the ranges can be upward 750 mV allowing for a much better corrosion resistance of the material.
For review of the complete paper published in Pharmaceutical Engineering November / December 2011 issue, visit our Literature page.