| TIAN Yuan,PU Yanan,SUN Tianxiang,HOU Su,CHEN Shougang.Microbiologically Influenced Corrosion of Nickel Caused by Sulfate-reducing Bacteria under Different Levels of Headspace Volume[J],53(4):68-76, 97 |
| Microbiologically Influenced Corrosion of Nickel Caused by Sulfate-reducing Bacteria under Different Levels of Headspace Volume |
| Received:December 22, 2022 Revised:March 30, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.04.006 |
| KeyWord:Ni biofilm sulfate-reducing bacteria headspace microbiologically influenced corrosion pitting corrosion |
| Author | Institution |
| TIAN Yuan |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| PU Yanan |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| SUN Tianxiang |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| HOU Su |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
| CHEN Shougang |
School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
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| Abstract: |
| Nickel (Ni), an important alloying element, has been widely added to alloys to improve their corrosion resistance, and strengthened Ni-based alloys are commonly used in industries such as oil, gas, and offshore engineering, but still face the microbiologically influenced corrosion (MIC). The volume ratio of headspace/broth can affect microbial activity, thereby affecting the metabolism of biofilm and the process of extracellular electron transfer (EET). The MIC mechanism of Ni induced by sulfate-reducing bacteria (SRB) with varied headspace volume was investigated to provide a basis for the corrosion protection of Ni-based alloys. The MIC behavior of Ni was evaluated by biological detection, surface analysis, and electrochemical analysis techniques. Different headspace volume of 10 mL, 90 mL, and 450 mL was regulated with glass bottles and glass beads of different sizes with a fixed broth volume of 200 mL. The sessile cell count of Desulfovibrio vulgaris was 107 cells/cm2 after the 3 d pre-growth. The D. vulgaris sessile cell count on Ni coupons in the anaerobic bottles with 10 mL headspace volume was 1.28×107 cell/cm2. The sessile cells count on Ni coupons in the 90 mL and 450 mL headspace volume increased by 213% and 288%, respectively compared with the 10 mL headspace. The fluorescence microscopy (FM) images also showed a relatively robust biofilm covering the Ni coupon surface. The corrosion rate of Ni coupon was analyzed by weight loss data and the maximum pitting depth distribution statistics (with a confocal laser scanning microscope, CLSM). The weight loss of Ni coupons with a headspace volume of 90 mL (1.1 mg/cm2) and 450 mL (1.4 mg/cm2) was 1.1 times and 1.4 times that of Ni coupons with the 10 mL headspace (1.0 mg/cm2), respectively. The maximum pit depth after the 7 d incubation was 2.7 µm with 10 mL headspace volume, and the corresponding pitting depth increased 1.6 times (4.2 µm) and 2.3 times (6.1 µm) for 90 mL and 450 mL headspace, respectively. With a fixed broth volume of 200 mL in all bottles, a larger headspace meant that more H2S escaped to the headspace, which reduced the toxicity of H2S in broth to D. vulgaris. The larger the headspace volume, the higher the D. vulgaris sessile cells count, the deeper the pitting pits, and the higher the corrosion rate. The lowest polarization resistance (Rp) value during the 7 d incubation period occurred in the headspace of 450 mL. Meanwhile, the lowest low-frequency resistance was obtained at a headspace volume of 450 mL. Corrosion current density (Jcorr) from potentiodynamic polarization data after the 7 d incubation with the 450 mL headspace (7.64× 10–6 A.cm–2) was more than 1.5 times and 2.1 times of that for headspace volume of 10 mL and 90 mL, respectively. The corrosion thermodynamic analysis and experimental data indicated that D. vulgaris utilized elemental Ni to replace the organic carbon source (lactate) as the electron donor. It is thermodynamically favorable to use the electrons released by extracellular Ni oxidation to reduce sulfate in D. vulgaris cytoplasm. Thus, Ni MIC by D. vulgaris belongs to EET-MIC. |
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