Investigation on corrosion of zinc ribbon under alternating current

Zinc ribbon has been widely used for alternating current (ac) mitigation of pipeline. However, little is known about corrosion of zinc under ac. In this work, the corrosions of zinc under various ac in two scenarios, i.e. with or without direct current (dc) decoupler, were investigated in 4 g L-1 Na2SO4 simulated backfill solution by weight loss tests, low angle X-ray diffraction measurements and electrochemical measurements. It was found that ac accelerated corrosion of zinc dramatically in both scenarios, and it is worth noting that dc density between zinc and pipeline steel increased with ac in the scenario without dc decoupler. Consequently, corrosion rate of zinc was much larger than that in the scenario in which dc decoupler was used. Besides, the charge transfer resistance of zinc decreased considerably due to ac in both scenarios, which would largely increase corrosion rate.