Biocorrosion or microbiologically influenced corrosion (MIC) is a major problem in many industries, especially the oil and gas industry. Biofilms are the culprits of MIC. In this work, D-amino acids were used to enhance two biocides, namely alkyldimethylbenzylammonium chloride (ADBAC) and tributyl tetradecyl phosphonium chloride (TTPC), to treat a tough and corrosive field biofilm consortium on C1018 carbon steel coupons. An equi-mass D-amino acid mixture (“D-mix”) of four D-amino acids (Dmethionine, D-tyrosine, D-leucine, and D-tryptophan) at a total concentration of 50 ppm (w/w) was tested. The cocktails of 60 ppm ADBAC + 50 ppm D-mix and 40 ppm TTPC + 50 ppm D-mix both achieved a 3-log reduction of the sessile cell count of sulfate reducing bacteria (SRB) in the 7-day biofilm prevention test compared with a 1-log reduction achieved by 60 ppm ADBAC and 40 ppm TTPC alone separately. In the 3-hour biofilm removal test that started with mature biofilms on C1018 carbon steel coupon surfaces, the cocktails of 150 ppm ADBAC + 50 ppm D-mix and 100 ppm TTPC + 50 ppm D-mix both achieved a 2-log reduction compared with a 1-log reduction achieved by 150 ppm ADBAC and 100 ppm TTPC alone separately. In all the tests, D-mix alone showed no log reduction. Scanning electron microscope images and confocal laser scanning microscope images supported the results.
Key words: downloadable, biocide, D-amino acid, biofilm, microbiologically influenced corrosion