Corrosion Rate Of Steel Coupons Research Articles

A comparative study of the corrosion of Q235 carbon steel in six different strains of marine-isolated sulfate reducing prokaryote

Biocorrosion in marine environments is often associated with biofilms of sulfate reducing prokaryotes. However, the corrosion behaviors of steel differed greatly between the bacterial species. In this study, six strains of sulfate reducing prokaryote including 3 strains of strictly anaerobic bacteria and 3 strains of facultative anaerobic bacteria were isolated from the steel rust immersed in Sanya, China. The corrosion behavior of Q235 carbon steels by isolated six strains was studied by weight loss analysis, electrochemistry measurements, and surface morphology observation. In addition, the relationship between bacterial corrosivity and strain type was investigated. The results indicated that there is no direct relationship between the corrosivity of bacteria and strain type, whether the bacteria were strictly anaerobic or not. The corrosion rates of steel coupons fluctuated with the strain properties and soaking time. Among the strains tested, the strains belonging to Proteobacteria had relatively high corrosion rates on steel coupons, whereas, strain Virgibacillus Dokdonensis of Firmicutes has the lowest corrosion rate. The results provide a guiding basis for exploring the mechanism of microbial corrosion and controlling marine microbial corrosion.

Fluctuation in deep groundwater chemistry and microbial community and their impact on corrosion of stainless-steels

Low and intermediate level radioactive waste produced during the operation and decommissioning of nuclear power plants is disposed of in an underground geological repository. The majority of metallic waste is made of various stainless-steels and carbon steel. Microbial communities and groundwater composition in deep bedrock at repository sites were believed to stay stable over time, allowing the prediction of evolution of the repository environment. However, a two-year survey of chemical components and microbial community composition within deep bedrock revealed changes in both. An in situ corrosion monitoring system was developed to monitor real-time corrosion rates of two stainless-steel grades (AISI 304 and 316) to study the evolution of corrosion, and correlation between environmental changes and corrosion rate. Surprisingly, higher corrosion rates of steel coupons were detected in the higher alloyed stainless-steel grade 316 compared to the lower alloyed grade 304. Pitting was the main corrosion form. Sulphate reducing bacteria and methanogenic archaea were enriched on surfaces of both types of steel coupons. These microbes likely have a role in the corrosion of stainless-steel in this environment. The changes in groundwater conditions and microbial communities within deep bedrock groundwater at this repository site may have implications for the nuclide release and transport of radioactive material and the long-term evolution and safety of this repository and continental repositories in general and thus needs to be thoroughly understood.

Electrochemical mechanisms of corrosion influenced by sulfate-reducing bacteria in aquatic systems

It has been recognized that sulfate-reducing bacteria (SRB) play a significant role in corrosion by accelerating the electrochemical processes whenever environmental conditions are favouable. In this study, the polarization test and the dual-cell test were conducted to result in a better fundamental understanding of corrosion influenced by SRB. The polarization test showed that the effects of SRB and anodic or cathodic depolarization on corrosion were insignificant when 1.5 mM of CaCO 3 was added to the solution. The instantaneous corrosion rates of steel coupons immersed in the SRB-inoculated solution were 1.5–2.5 times greater than those obained in the sterile solution. The polarization curves obtained in the SRB-inoculated solution with 0.5 mM sulfate concentration indicated that both anodic and cathodic depolarization occurred on steel coupons. However, only cathodic depolarization was obtained in the SRB-inoculated solution with 0.1 mM sulfate concentration, due to low hydrogen sulfide production. From the dual-cell test, the electron was transferred from the steel coupon in the sterile solution toward the steel coupon immersed in the SRB-inoculated solution, probably due to the electron consumption by SRB. When CaCO 3 was added to the same solution, no reactions occurred on the coupons exposed to either the SRB-inoculated solution or the sterile solution after 20 h of inoculation.

Bacterial Corrosion of Offshore Structures

Abstract Reports published by the British Admiralty and by individuals in England and the United States, show-that sulfate-reducing bacteria can cause corrosion of iron under some conditions. Because of the importance of maintaining in good condition the steel piling of offshore structures in the Gulf of Mexico a research investigation of the possibility of bacterial corrosion of these installations was inaugurated. Laboratory tests were directed toward developing fairly pure cultures of sulfate-reducing bacteria and using them in both natural muds and synthetic culture media for the purpose of determining their effect on the corrosion rate of steel coupons under anaerobic conditions. Maximum corrosion rates obtained were of the order of 0.001 inch per year. Several assemblies of twenty coupons each were installed at a marine platform approximately seven miles off Grand Isle, Louisiana; the coupons on each assembly were spaced to extend a few feet above and a few feet below the mud line. Somewhat similar ...