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42 DECEMBER 2016 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 55, NO. 12 CHEMICAL TREATMENT Know Your Enemy Defeat preferential weld corrosion! Learn what you're up against and how to eff ectively mitigate PWC. Preferential Weld Corrosion of Carbon Steels BY Dale McIntyre & Mohsen Achour Now available at corrstore.com depending on the requirement. The effec- tiveness of the biocide can be tested in a laboratory test. Slime formers create a biofilm that pro- tects other MIC-causing bacteria. Biocides may not reach bacteria when slime is pres- ent. Shock dosing should be carried out— but only after removing slime by pigging. Fo r e x a m p l e , a s h o c k d o si n g w a s planned for an injection water line with 100 ppm of Biocide A for 4 h. In the laboratory test, injection water was prepared by add- ing bacteria from positive vials of testing water. Biocide A was injected at the same planned shock dosage rate and time (100 ppm). After that, the treated sample was injected into the culture bottles following the serial dilution method . These vials should not give positive results (i.e., a bac- terial presence should not be there), at least up to the period of the next shock dosing. When shock dosing in the field, the in- jection dosage should be maintained at a constant rate and without much variation for the stipulated shock dosing period. Ad- ditionally, the chemical injection system should be maintained and monitored for consistent biocide injection. Conclusion Following a standard method and every step mentioned previously can provide the exact bacteria count; and with that, a bio- cide chemical treatment program can be established for preventing MIC. Reference 1 NACE Standard TM0194-2014, "Field Moni- toring of Bacterial Growth in Oil and Gas Systems" (Houston, TX: NACE International, 2014). Bibliography Borenstein, S.W. Microbiologically Inf luenced Corrosion Handbook. New York. NY: Wood- head Publishing, Ltd., 1994. Murthy, T.L.N. "A Systematic Approach to Pre- vent Internal Corrosion of Pipelines." MP 46, 12 (2007). Murthy, T.L.N. "Monitoring of Chemical Treat- ment is Essential to Prevent Internal Corro- sion." MP 53, 9 (2014). Murthy, T.L.N. and G.K. Naidu. "A Sour Gas Prob- lem in Sweet Crude Oil Storage Tanks." MP 54, 2 (2015). Peabody, A.W. and R . Bianchetti, ed. Peabody's Control of Pipeline Corrosion. 2nd ed. Hous- ton, TX: NACE, 2001. Roberge, P. Corrosion Basics—An Introduction. 2nd ed. Houston, TX: NACE, 2006. TATA L.N. MURTHY is the assistant general m a n a g e r — O G T a t G S P C , L t d . , P. Mallavaram, Tallarevu Mandal, E.G. Dist., Andhra Pradesh 533463, India, e-mail: lnmurthytata@gmail.com. He has more than 15 years of experience in chemistry and corrosion of oil and gas production operations, including experience estab- lishing a chemistry laboratory and corro- sion monitoring system. He has an M.S. degree in applied chemistry and an M.B.A. in operations, and is a C.Chem (Chartered Chemist) and MRSC (Royal Society of Chemistry, London). Murthy is a Life Fellow of the Indian Council of Chemists, India; Life Fellow of the Indian Chemical Society, I n d i a ; N A C E I n t e r n a t i o n a l - c e r t i f i e d Corrosion Technologist; and ASNT-certified NDT Level II (PT, MT, RT, UT). He is the author of several journal articles and is an 11-year member of NACE. MP — Cathodic Protection Problem for a Gas Pipeline Near a Compressor Station Developments in Zinc-Based Anticorrosion Coatings Managing Cooling Systems to Prevent Silica Deposition Case History: Preheater Tubes in a Heat Recovery Boiler Influence of Ball Milling on Electrochemical Properties in Lithium-Ion Batteries