Effects of alternating current on microbiologically synergistic corrosion of pipeline steel X80 applied by elastic stress

Microorganisms play an important role in multi-factor synergistic corrosion. The synergistic effects of which are greatly stronger than elastic stress and alternative current. Changes of alternative current directly dominate the effect of microbial synergy. With increasing AC current density, corrosion rate of pipeline steel X80 increased first and then decreased, reaching a peak at 100 A m⁻². Number of SRB cells vaired as a function of AC current density. Lower current density promoted SRB growth while high current density inhibited SRB growth. When sessile cells are more than 10⁵ cell cm⁻², the dominant role of microorganisms is strong, and corrosion rate increases with current density. The maximum value is reached at 100 A m⁻². However, when the cells are less than 10³ cell cm⁻², the dominant effect is greatly reduced, leading to a reduction in the synergistic effect of the multi-factor, and finally reduced corrosion rate to 200 A m⁻².