Corrosion Acceleration of Printed Circuit Boards With an Immersion Silver Layer Exposed to Bacillus cereus in an Aerobic Medium

Effect of Pseudomonas aeruginosa on corrosion of X65 pipeline steel

Microbiologically influenced corrosion (MIC) has caused great losses to many industries. This paper aimed to study the corrosion behavior of P. aeruginosa on X65 steel. The corrosion behavior of P. aeruginosa on X65 steel under aerobic and anaerobic conditions was studied by scanning electron microscopy, energy dispersive spectrometer and electrochemical analysis techniques. The results showed that the corrosion rate of X65 steel in bacterial environment is higher than that in sterile environment. In anaerobic environment, the corrosion of P. aeruginosa is mainly secreted acidic metabolites, and alkaline substances are corroded in aerobic environment. In general, the corrosion of X65 steel by P. aeruginosa in aerobic environment is more serious than that in anaerobic environment.

The influence of the marine Bacillus cereus over carbon steel, stainless corrosion, and copper coupons

The present study evaluated the influence of the marine bacteria Bacillus cereus Mc-1 on the corrosion of 1020 carbon steel, 316L stainless steel, and copper alloy. The Mc-1 strain was grown in a modified ammoniacal citrate culture medium (CFA.ico-), CFA.ico- with sodium nitrate supplementation (NO_3-), and CFA.ico- with sodium chloride supplementation (NaCl). The mass loss and corrosion rate were evaluated after the periods of 7, 15, and 30 days. The results showed that in CFA.ico- and CFA.ico- medium added NO_3- the corrosion rates of carbon steel and copper alloy were high when compared to the control. Whereas the medium was supplemented with NaCl, despite the rates being above the averages of the control system, they were considerably below the previous results. In general, the corrosion rates induced by Mc-1 on 316L coupons were below the results compared to carbon steel and copper alloy. When analyzing the corrosion rate measurements, regardless of the culture medium, the corrosion levels decreased consistently after 15 days, being below the levels evaluated after 7 days of the experiment. Our analyses suggest that B. cereus Mc-1 has different influences on corrosion in different metals and environmental conditions, such as the presence of NO_3- and NaCl. These results can help to better understand the influence of this bacteria genus on the corrosion of metals in marine environments.

Corrosion Behavior of AISI 1045 Steel in Seawater in the Presence of Flavobacterium sp

A systematic comparison study was carried out to investigate the effect of Flavobacterium sp. on AISI 1045 steel corrosion by weight loss, fluorescence microscopy (FM), surface analysis, cell count, pH measure, electrochemical impedance spectroscopy (EIS), and polarization curves. The impedances were considerably increased by Flavobacterium sp. between 1 and 7 day exposure and after 30 day exposure but considerably decreased by Flavobacterium sp. after 15 and 21 day exposure, which were supported by the I_corr results and the weight loss data. Furthermore, the biofilm was formed on the coupons. The pH values were considerably decreased by Flavobacterium sp. after 15 and 21 day exposure. The results proved that Flavobacterium sp. decreased the corrosion rates between 1 and 7 day exposure and after 30 day exposure and increased the corrosion rates between 15 and 21 day exposure, which could be ascribed to the protective biofilm and the secreted corrosive acid, respectively. In addition, Flavobacterium sp. considerably increased the pit numbers, the maximum pit depths, and the corresponding widths and considerably decreased the E_pit values. Importantly, the coverage and the heterogeneity of the biofilm were positively correlated with the increases in the maximum pit depths and the corresponding widths and the decreases in the E_pit values by Flavobacterium sp. The results demonstrated that Flavobacterium sp. increased the pitting corrosion, which could involve the heterogeneous biofilm cover.