Abstract
The corrosion mechanism of carbon steel under deposit in the presence of sulfate reducing bacterium (SRB) Desulfotomaculum nigrificans was studied using surface analysis, weight loss and electrochemical measurements. Results showed that both the general corrosion and localized corrosion were considerably promoted by SRB under deposit. The corrosion rate of steel in the presence of SRB was approximately 6 times of that for the control according to the weight loss measurements. The maximum corrosion pit depth in the presence of SRB was approximately 7.7 times of that of the control. Both the anodic and cathodic reactions were significantly accelerated by SRB. A galvanic effect in the presence of SRB due to the heterogeneous biofilm led to serious localized corrosion.
Highlights
In the oil and gas fields, pipeline steel corrosion resulted in large economic losses but caused safety related accidents
The weight loss increased by approximately 6 times in the presence of sulfate reducing bacterium (SRB), with a higher weight loss (7.9 ± 0.9 mg cm−2). These results indicated that SRB considerably accelerated under deposit corrosion (UDC) corrosion
After 14 days of incubation, the anodic current density of electrode 5 is 1.49 × 10−6 mA cm−2. These results indicate that both general corrosion and localized corrosion occurred in UDC in the absence of SRB
Summary
In the oil and gas fields, pipeline steel corrosion resulted in large economic losses but caused safety related accidents (da Costa Mattos et al, 2016; Feng and Cheng, 2017). Some researchers have investigated UDC under different testing conditions and with different deposits. Han et al (2013) studied steel corrosion under sand deposit, and their results showed that corrosion pits were initiated by a galvanic effect. Standlee et al (2011) found that FeS deposit could considerably accelerate steel corrosion compared with those in the sand deposit, and serious pitting corrosion with mill scale was observed. Hoseinieh et al (2016) investigated steel corrosion covered by calcareous deposit using electrochemical noise, and found that there were two different stages for localized corrosion processes. The UDC is chemically and physically different from the bare steel corrosion in the absence of deposit, and the concentration of aggressive species and pH differ (Huang et al, 2010)
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