Metabolomic profiling differentiates rates of corrosion for mooring chains

摘要

Biofilm-exacerbated marine corrosion of metallic materials is an ongoing problem in both onshore and offshore systems. In recent years, inspections of the mooring chains on several floating production units worldwide revealed severe localized corrosion attack. Microbiologically-influenced corrosion (MIC) has been implicated as a cause of chain deterioration. Over the past few years a number of pilot studies and Joint Industrial Projects involving major oil companies, off-shore engineers, universities and chain manufactures has been initiated to investigate the cause of chain deterioration and to evaluate mitigation strategies. In here described study, coupons manufactured from a chain grade carbon steel prepared by two different mooring chain suppliers and representing 3 different types of treatments, unprotected, coated, and cathodically protected, were exposed for over 60 days at four different geographical locations coded C, G, M and N to investigate the effect of bio films on corrosion. For each manufacturer and type f treatment five different coupons (biological replicates) were deployed using a specially designed kit. Biofilms removed from coupon surfaces underwent chemical extraction and concentration procedures. Extracts were analyzed, in triplicates, using an Agilent 1290 ultra-high-performance liquid chromatograph (UPLC) coupled to an Agilent 6545 quadrupole-time-of-flight, high resolution mass spectrometer (QTOF/HRMS). A robust workflow for the analysis of the UPLC/HRMS data from these extracts was developed in-house, leading to the detection of thousands of compounds. The reproducibility of the metabolomes obtained from coupon replicates was studied and coupon-to-coupon variability compared using statistical tools such as principal component analysis. Results revealed significant correlation between the severity of corrosion and the metabolomic profiles between locations, as well as between untreated, coated and cathodically protected coupons. The study demonstrates that metabolomics can serve as a tool not only for diagnosing MIC but also for its prediction and for monitoring the efficacy of MIC prevention and protection measures.