Hybrid treatment of ultrasound and ultraviolet radiation to mitigate microbial corrosion on API 5L X70 carbon steel

Abstract

The destructive effects of microbial corrosion of carbon steel in pipes have been widely found in soil and water environment. Numerous studies have proven the ability of ultraviolet (UV) radiation as an alternative technique to substitute hazardous chemical biocides in disinfecting microbes for pipelines system. Unfortunately, the radiation efficiency is hindered due to the presence of suspended particles in the environment. Moreover, the UV treated microbes would undergo photo-reactivation which allows the damaged deoxyribonucleic acid (DNA) to be repaired or rejuvenated. In order to counter these drawbacks, a recent study recommended that combining UV radiation with ultrasound (US) technology can led to its irreversible damage inflicted to the microbe’s cell wall. However, information on the efficiency of the integrated treatment between US and UV and the influences of its variables on corrosion process is scarce and limited, thus restricting any efforts to explore the potential application of UV combined with US as an alternative for chemical biocide replacement. Present study aimed to investigate the optimal performance of integrated treatment using US with UV technology in controlling microbial corrosion caused by sulfate reducing bacteria (SRB) strain. The investigation utilized one pure SRB strain known as Desulfovibrio vulgaris (ATCC 7757) and focused on static treatment condition. Four experimental stages were involved in order to attain the research objectives and aim. The metal loss of API 5L X70 carbon steel coupon was recorded systematically, then the corrosion rate of steel coupon in untreated and treated environment was determined using weight loss technique. The corrosion rate of steel coupon in biotic sample was found approximately 34% higher than abiotic sample. A total of 438 steel coupons were used throughout research duration. Based on screening design, the findings have successfully identified the most influential variables of the hybrid treatment which are US exposure time, UV exposure time, distance of UV lamps to sample, amplitude of US, and volume of sample. In addition, interactions between the variables were also considered when performing the hybrid treatment. Subsequently, one microbial corrosion mitigation empirical model was derived sequential to the hybrid treatment using response surface method (RSM) with correlation coefficient (R2) of 72%. Regardless of the moderate value of R2, since it has statistically significant predictors, it is still possible to draw important conclusions about how changes in the predictor values are associated with changes in the response value. Results also have confirmed that the hybrid treatment outperformed individual UV and US treatment based on the reduction of corrosion rate by approximately 50%. On the other hand, the simultaneous (US+UV) reactor set-up performed effectively with corrosion rate 0.0108 mm/year as compared to 0.0174 mm/year by non-simultaneous (US-UV) reactor set-up. These corrosion values are much lower than the control sample and non-hybrid treated sample. Valuable findings from present research shows promising future for non-physical corrosion treatment since this can serve as an impetus for the transfer of the integrated technology from its infancy level to the real-world practice of corrosion mitigation in the oil and gas industry.