Papers by Keyword: Microbiologically Influenced Corrosion (MIC)

Abstract: First case describes hot temperature corrosion of 1.4841 heat resisting steel, which was caused by formation of the low melting nickel sulphide (LME effect).In the second case centrifugally cast tubes of Ø52.6 x 5.8 mm size made of 25/35 CrNi steel, which are exposed to high temperature and to severe reducing environment (carbon activity ac >> 1), are concerned. In such condition a graphitization may start, that results in the disintegration of its structure, which is called ,,metal dusting”.The third case is dealing with an attack of the 1.4301 steel pipe welds by microbiologically influenced corrosion. After short service time several leakages of water were revealed. It was proved, that failure was caused by microbiologically influenced corrosion of sulphate-reducing bacteria (SRB) and not by an improper welding technology.

Abstract: The contribution summarizes some corrosion case studies of the welded steel structures, which happened in Slovakia last years. Features of cracking are illustrated on real cases of breakdowns in the petrochemical industry (SSCC and PTA-SCC of stainless steel), at a cement works (LME of AISI 310 steel due to Ni₃S₂ attack ), at a gas pipeline (LME caused by remelted Cu) and in the water meters & tubes made of stainless steel (MIC).

Abstract: The corrosion behavior of duplex stainless steel immersed in nutrient-rich simulated seawater without deep sea bacteria and with deep sea bacteria (Erythrobacter pelagi sp.nov) was studied. The effect of chloride ions and presence of deep sea bacteria on corrosion resistance was investigated. The occurrence of localized corrosion (Viz. pitting and crevice corrosion) was examined using visual inspection and SEM-EDX. Electrochemical impedance spectra were used to study the effects of deep sea bacteria on duplex stainless steel and inferences were made. Most significantly was the reduction of pitting resistance potential with increase in exposure time.

Abstract: A range of stainless steels has been investigated for resistance to microbiologically influenced corrosion in seawater. The corrosion potential was monitored for stainless steel coupons exposed to sterilized seawater and to microbiologically active seawater, which showed the effect of the growth of microorganisms. Cyclic potentiodynamic polarization scans confirmed that 13%Cr stainless steel is very susceptible to localized corrosion under these conditions. 316L stainless steel was also quite susceptible to localized corrosion, whereas 2205 duplex stainless displayed good resistance to localized corrosion. Naturally occurring microorganisms in the seawater were shown to exacerbate the localized corrosion.

Abstract: The microbial corrosion behaviors of 10CrNiCu steel influenced by Thiobcillus ferrooxidans (T.f) were studied by microbiological, electrochemical and surface analysis method. The open circuit potential (E_ocp) and electrochemical impedance spectroscopy (EIS) of the 10CrNiCu electrodes were measured in immersion electrode way with and without T.f solution at the time of the 0, 2^nd, 7^th, 14^th and 21^st days, respectively. E_ocp of the electrode immersed in sterile medium shifted to negative potential with the immersion time while that for immersion in T.f solutions shifted negatively, then positively and finally negatively. EIS results were interpreted with different equivalent circuits of the electrode/biofilm/solution interface. The result of SEM indicated that, after 21 immersion days, there were different sizes of pits on the 10CrNiCu surface occurred in T.f solution while no evidence of the pitting corrosion was observed on the steel surface immersed in the sterile medium.

Abstract: A kind of sulfate-reducing bacteria was isolated from the actual marine environment, cultured and enriched for phylogenetic analysis by molecular biology methods, and observed under fluorescent microscopy and transmission electron microscopy to determine the species and morphology. Taking the bacteria as the main object, the influenced corrosion behavior of steels in marine environment was studied in follow-up experiments.

Abstract: Microbiologically Influenced Corrosion behavior of copper manganese aluminum alloy (CMA) were studied in the environment of sulfate-reducing bacteria (SRB). Surface topography of microorganism films were observed by using atomic force microscopy (AFM) and Scanning Electron Microscope (SEM), The result showed that number of SRB were a little, so that microorganism films can’t form in the surface of CAM; Microscopic structure was analyzed in the process corrosion, with increase of exposure time, selective corrosion occurred mainly on containing Al at a high level of β-phase and κ-phase. X-ray Photoelectron Spectroscopy (XPS) showed the main component of corrosion product was Sulphide. The change of Ecorr and corrosion current density in culture medium containing SRB was greater than it in 3.5% NaCl. It showed that the selective corrosion of the copper was accelerated by the metabolism substance. The content of sulfide was increasing with exposure time increasing.

Abstract: Microbiologically influenced corrosion (MIC) is a serious problem that continues to plague many industrial systems. In this study, a method to prevent MIC by the use of an azole-type organic compound on the metal substrates was studied. Inhibition of MIC of mild steel and stainless steel 316 by 2-Methylbenzimidazole (MBI) in seawater with sulphate-reducing bacteria (SRB) was investigated using electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). MBI was shown to be an effective inhibitor in controlling MIC by two strains of sulphate-reducing bacteria: Desulfovibrio desulfuricans, and a local marine isolate. EIS analysis shows an increase in charge transfer resistance for both mild steel and stainless steel 316 after the addition of MBI in the aqueous solution. AFM analyses show a decrease in the surface roughness and pit depth after the addition of MBI. Of the two bacterial strains, it is found that MBI is more effective in the inhibition of corrosion by D. desulfuricans. At a concentration of 1mM, MBI shows a higher MIC inhibition effect on stainless steel 316 (corrosion inhibition 99.5%) than on the mild steel (corrosion inhibition 59.4%). These results indicate that MBI shows potential application in the inhibition of MIC of metal substrates.

Abstract: Microbially influenced corrosion (MIC) of steel has gained increasing attention in recent years because the damage caused by this process is a significant cost factor for industry. Consequently, inhibition of corrosion and especially the development of corrosion protective films is an important present-day research topic. In this connection, application of microbially produced EPS for mitigating steel corrosion is an innovative idea. However, observations of ”protective” biofilms on metallic surfaces have been previously reported. Their inhibiting effect is generally thought to be caused by oxygen depletion or the formation of passivating layers. In contrast to many conventional corrosion protective methods, EPS or EPS-derived agents would be a cheap and environmentally friendly solution. Extensive research activities are still required, before biofilms or cell-free EPS can be used for corrosion protection on larger scale. In this study, we are developing a novel EPS-based corrosion protection method for unalloyed and corrosion resistant steel in aqueous media, which is based upon the application of microbial metabolic products. EPS of various sulfatereducing bacteria and other microorganisms are investigated for their inhibiting effect. The extent of such inhibition is evaluated in a model test system, in which different steels are subjected to corrosive conditions under sulfate-reducing conditions. To elucidate the protective mechanisms, comparative analyses of the chemical composition of the applied EPS are performed.