Mechanical property degradation of X80 pipeline steel due to microbiologically influenced corrosion caused by Desulfovibrio vulgaris.

Apart from pinhole leaks, MIC (microbiologically influenced corrosion) can also cause catastrophic failures such as pipe ruptures and support beam collapses due to mechanical property degradation or stress corrosion cracking. In this work, X80 pipeline steel dogbone coupons and square coupons were immersed in 150 ml broths containing Desulfovibrio vulgaris, a common corrosive sulfate reducing bacterium (SRB), for up to 14 days. The headspace volumes in the anaerobic bottles were increased from 150 ml to 200 ml and 300 ml to increase MIC severity. After 14 days of SRB incubation in ATCC 1249 culture medium with X80 coupons at 37°C, the sessile cell counts were 6.5 × 107 cells cm-2 for 150 ml, 2.3 × 108 cells cm-2 for 200 ml and 1.4 × 109 cells cm-2 for 300 ml headspace volumes, respectively owing to reduced H2S cytotoxicity in the broth with a larger headspace because it allowed more biogenic H2S to escape from the broth. Weight losses were 1.7 mg cm-2, 1.9 mg cm-2 and 2.3 mg cm-2 for 150 ml, 200 ml and 300 ml headspace volumes, respectively. The corresponding pit depths were 2.6 µm, 4.2 µm and 6.2 µm for 150 ml, 200 ml and 300 ml headspace volumes, respectively. Electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and potentiodynamic polarization results corroborated the increasing weight loss and pitting data trends as a result of increased headspace. Tensile testing of dogbone coupons after the 14-day SRB immersion test indicated that more severe MIC pitting led to a higher ultimate strain loss by up to 23% (300 ml headspace) compared to the abiotic control, while the ultimate strength losses for all headspace volumes were quite small (3% and lower).

Characteristic and Mechanistic Investigation of Stress-Assisted Microbiologically Influenced Corrosion of X80 Steel in Near-Neutral Solutions.

The behavior and mechanisms of the stress-assisted microbiologically influenced corrosion (MIC) of X80 pipeline steel induced by sulfate-reducing bacteria (SRB) were investigated using focused ion beam-scanning electron microscopy (FIB). Electrochemical results show that SRB and stress have a synergistic effect on the corrosion of X80 steel. SRB accelerated the transformation of Fe3O4 into iron-sulfur compounds and may have caused the film breakage of X80 steel products. The obtained FIB results provide direct evidence that SRB promotes the corrosion of X80 steel.

A modulation approach for covalent organic frameworks: Application to solid phase microextraction of phthalate esters.

A modulation approach with 4-hydroxybenzhydrazide as the modulating agent was designed for constructing 2,4,6-triphenoxy-1,3,5-benzene-based covalent organic frameworks (COFs). The COFs materials were employed as solid phase microextraction (SPME) coatings for the extraction of phthalate esters (PAEs). Various experimental conditions including extraction temperature, extraction time, salt concentration, and desorption time were investigated and optimized. The introduction of modulating agent into the synthesis of fibers significantly enhanced the extraction efficiency towards PAEs. The linear range was 1-100 µg L‒1 and the detection limits in the range of 0.032-0.451 µg L‒1 were achieved with good linearity ranged from 0.9904 to 0.9970. Inter-batch and intra-batch relative standard deviations were in the ranges of 0.83-4.67% and 3.08-9.73%, respectively. Moreover, the developed coating fibers were used for the extraction of PAEs in water samples and satisfactory recoveries were achieved.

A triazine based organic framework with micropores and mesopores for use in headspace solid phase microextraction of phthalate esters.

A dual-pore covalent organic framework (COF) that contains micropores and mesopores was prepared from 2,4,6-triphenoxy-1,3,5-triazine (TPT). A building block is used in which double linking sites were introduced at each branch of a C3-symmetric skeleton. The COF is shown to be a viable coating for fibers for solid-phase microextraction of phthalic acid esters (PAEs). Its high specific surface, high hydrophobicity, and wide pore size distribution of a TPT-COF coated fiber result in extraordinarily powerful extraction of PAEs. The enrichment factor is up to 7790 under optimum conditions. The method has detection limits that range between 5 and 95 ng L-1. The inter-batch relative standard deviations are between 3.1 and 10.9%, and those for intra-batch assays are from 0.8 to 4.7%. The TPT-COF coated fibers were applied to the extraction of PAEs from (spiked) juice samples, and satisfactory recoveries were achieved. Graphical abstract TPT-COF coated SPME fiber was prepared for the preconcentration of phthalate esters coupled with GC-FID.