Influence of Shewanella algae and calcium-magnesium deposit layer on the corrosion mechanism of X80 carbon steel in marine environment
Yufeng Shen, Rongyao Ma, Changgang Wang, Rui Li, Jie Huang, Junhua Dong, Dake Xu
Abstract
• Both Shewanella algae and compact calcium-magnesium deposit layer exert an inhibitory effect on the corrosion of X80 steel. • Metabolic activities of Shewanella algae have the potential to destabilize the calcium-magnesium deposit layer. • The impact of Shewanella algae and deposit layer on the corrosion of X80 steel exhibits a time-dependent manner. In the marine environment, the surface of X80 steel under cathodic protection is highly prone to forming a dense calcium-magnesium deposit layer and adsorbing a large amount of Shewanella algae ( S. algae ), thus facing a severe risk of under-deposit microbial corrosion. This paper investigates the effect of the S. algae and calcium-magnesium deposit layer on the corrosion behavior of X80 steel. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), confocal laser scanning microscopy (CLSM), X-ray photoelectron spectroscopy analysis (XPS), and electrochemical techniques were utilized. Research findings indicate that the corrosion process was significantly reduced in the presence of S. algae compared to the calcium-magnesium deposit layer. When both coexist, they synergistically inhibit corrosion in the initial stage; however, prolonged immersion leads to the disruption of the calcium-magnesium deposit layer by S. algae ’s metabolic activities, eliminating their synergistic inhibitory effect and resulting in a corrosion rate surpassing the media containing only S. algae .