Influence of Shewanella algae and calcium-magnesium deposit layer on the corrosion mechanism of X80 carbon steel in marine environment

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.