Corrosion of Stainless Steel Conductor Rolls in a Continuous Sheet Electrogalvanizing Line

Conductor rolls carry electrical current from steel strip during plating on a continuous electrogalvanizing line. Wear of type 316L (UNS⁽¹⁾ 31603) stainless steel (SS) sleeves on the conductor rolls can lead to increased line downtime and higher operating costs. We conducted laboratory tests to examine the hypothesis that some fraction of conductor roll wear is caused by corrosion that is accelerated by repeated cycles of coupling and uncoupling of the type 316L SS sleeve to zinc and exposure to a dilute sulfuric acid rinse solution. It was found that coupling to zinc causes reduction of the passive film on type 316L SS. Upon subsequent uncoupling, type 316L SS undergoes an interval of active corrosion prior to repassivation. When the time between uncoupling and recoupling is less than the time needed for repassivation, corrosion of type 316L SS is increased. We found that hydrogen peroxide accelerates the rate of repassivation and that it decreases corrosion of type 316L SS during cyclic coupling to zinc. Finally, in full-scale trials conducted on an electrogalvanizing line, additions of 500 to 1000 ppm of hydrogen peroxide to the rinse solution decreased losses of the type 316L SS conductor roll sleeves by 50 percent.