Normally passive metals when exposed to oxidizing halide environments can suffer from pitting and crevice corrosion. By the application of a direct current the structure potential can be shifted back to the passive region from the transpassive region. This method is used extensively on stainless steel bleach washer facilities in the pulp and paper industry. Stainless steel flue gas scrubbers and brine evaporators have also been protected using this method. In effect this technique up-grades the corrosion resistance of passive metals making their corrosion resistance comparable to higher grade alloys.
Figure: Typical polarization behaviour for stainless steel in an oxidizing chlorine environment.
source: http://www.westcoastcorrosion.com/service%20pap%20protection.htm
Figure: Typical polarization behaviour for stainless steel in an oxidizing chlorine environment.
source: http://www.westcoastcorrosion.com/service%20pap%20protection.htm
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