Abstract
Corrosion is a severe problem for steel structures in humid environments. In particular, humidity usually triggers the surface adhesion of microorganisms, leading to microbiologically induced corrosion. This study aims to explore the effect of bacterial biofilm formation on the pitting corrosion of stainless steel. This research uses electrochemical methods to obtain indirect evidence of the pitting corrosion of steel. In addition, in order to obtain direct evidence of the pitting corrosion of stainless steel, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the dimensional morphology of the stainless steel after pitting. It was shown that the bacterial adhesion increased with the pH and temperature, which significantly increased the surface roughness of the stainless steel. Electrochemical analysis revealed that the formation of biofilm greatly destroyed the oxide film of 304 SS and accelerated the corrosion of stainless steel by forming an oxygen concentration battery. SEM and AFM analyses showed cracks and dislocations on the surface of stainless steel underneath the attached bacteria, which suggested a direct role of biofilm in corrosion induction. The results presented here show that the bacterial biofilm formation on the steel surfaces significantly accelerated the corrosion and affected the pitting corrosion process of the steel structure.
Highlights
Corrosion has long been a major concern for steel structures
We investigated the effects of different environmental factors—including pH, temperature, and culture age (90 days)—which directly affect the extent of the initial adhesion of typical bacteria and bacterial biofilm formation
304 stainless steel (304 SS) were polished to a mirror finish, since surface topography is an important factor affecting the bacterial bacterial attachment attachment to to surfaces surfaces prior prior to to biofilm biofilm formation formation [29,30]
Summary
Corrosion has long been a major concern for steel structures. In some harsh environments—for instance, in humid service environments—microorganisms attach to steel surfaces and develop highly organized communities known as biofilms [1,2,3]. Humidity has been one of the major concerns for the maintenance of steel-structured high-voltage transmission line towers in southern China. Biofilm formation is a multi-stage process, with the adhesion of microorganisms such as bacteria as one of the most important steps [4]. Depending upon where they grow, these bacteria can be beneficial to wastewater treatment [5] or troublesome in biomaterial-related infections [6] and engineering equipment fouling and corrosion [7]. Induced corrosion problems afflict water-handling operations and manufacturing processes in oil and gas production, pipelining, refining, petrochemical synthesis, Coatings 2020, 10, 983; doi:10.3390/coatings10100983 www.mdpi.com/journal/coatings
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