Materials Performance

MAY 2015

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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10 MAY 2015 MATERIALS PERFORMANCE THE BLOG NACE INTERNATIONAL: VOL. 54, NO. 5 NACE INTERNATIONAL: VOL. 54, NO. 5 EDITORIAL D I R E C TO R, CO N T E N T D E V E LO P M E N T/ Gretchen A. Jacobson MA N AG I N G E D I TO R T E C H N I C A L E D I TO R John H. Fitzgerald III, FN AC E T E C H N I C A L E D I TO R Norman J. Moriber, Mears Group, Inc. A S S O C I AT E E D I TO R Kathy Riggs Larsen CO N T R I B U TO R Husna Miskinyar GRAPHICS E L E C T R O N I C P U B L I S H I N G Teri J. Gilley CO O R D I N ATO R G R A P H I C S D E S I G N E R Michele S. Jennings ADMINISTRATION C H I E F E X E C U T I V E O F F I C E R Rober t (Bob) H. Chalker G R O U P P U B L I S H E R William (Bill) Wageneck ADVERTISING S A L E S MA N AG E R Diane Gross, +1 281-228-6446 A S S I S TA N T S A L E S MA N AG E R Teresa Wright, +1 281-228-6472 ACCO U N T E X E C U T I V E S Erica R. Cor tina erica.cor, +1 281-228-6473 Brian Daley, +1 281-228-6455 Pam Golias, +1 281-228-6456 Jody Lovsness, +1 281-228-6257 Leslie Whiteman, +1 281-228-6248 A DV E RT I S I N G CO O R D I N ATO R Brenda Nitz, +1 281-228-6219 R E G I O N A L A DV E RT I S I N G S A L E S The Kingwill Co. R E P R E S E N TAT I V E S Chicago/Cleveland/ New York Area–, +1 847-537-9196 NACE International Contact Information Tel: +1 281-228-6200 Fax: +1 281-228-6300 E-mail: Firstser Web site: EDITORIAL ADVISORY BOARD Zahid Amjad Walsh University John P. Broomfield, FNACE Broomfield Consultants Raul A. Castillo Consultant Ir vin Cotton Ar thur Freedman Associates, Inc. Ar thur J. Freedman Ar thur Freedman Associates, Inc. David D. He PG&E Orin Hollander Holland Technologies W. Brian Holtsbaum Corsult Associates (1980), Ltd. Russ Kane iCorrosion, LLC Ernest Klechka CITGO Petroleum Corp. Kur t Lawson Mears Group, Inc. Lee Machemer Jonas, Inc. John S. Smar t III John Smar t Consulting Engineer L.D. "Lou" Vincent L.D. "Lou" Vincent PhD, LLC The following are excerpts f rom the NACE International Corrosion Net work (NCN) and NACE Coatings Net work . These are e-mail-based discussion g roups for corro- sion professionals , with more than 3 ,000 participants . The excerpts are selected for their potential interest to a large number of NACE members . They are edited for clarit y and leng th . Authors are kept anony mous for publication . Please be advised that the items are not peer-reviewed , and opinions and sug gestions are entirely those of the inquirers and respondents . NACE does not g uarantee the accuracy of the techni- cal solutions discussed . M P welcomes additional responses to these items . They may be edited for clarit y. For information on how to subscribe to these f ree list ser vers , click on the "Corrosion Central " link and then "Online Corrosion Communit y List Ser vers" on the NACE Web site: nace .org. Scale removal Q: I need your advice on a scale- related problem. One of our 14-in (102-mm) diameter oil production f lowlines, ~1 km long, has scaled up. Yellowish hard scale (mostly calcium carbonate [CaCO 3 ]) has built up in an asymmetrical pattern. It is thicker in the bottom—6 or 7 mm—and 2 or 3 mm in the upper side. It's not certain that the entire length is scaled up. The line has a three- phase f low, and the water cut is more than 80%. This scale developed before we started injecting scale inhibitor. The pipe is carbon steel (CS). Can someone share experience with acid-treating the line for scale removal and its down sides? Is there any other way to de-scale the line? A: Acid cleaning will liberate copious amounts of carbon dioxide (CO 2 ), which unless vented properly can be a major problem. Chelants such as ethylenediaminetetra- acedic acid (EDTA) will release the scale more slowly, but without the buildup of gas. It is also much more expensive. A: If your scale is radioactive, you may have to plan for safe disposal. A: Calcium and other carbonate scales (even iron oxides) can be removed by chemical cleaning with an inhibited sulfamic acid (HSO 3 NH 2 ) solution. In our plant we use a 7 to 10% inhibited sulfamic acid solution for clean- ing of CS and stainless steel piping and equipment. Te temperature during cleaning is 60 °C. Heating above 75 °C will hydrolyze the sulfamic acid solution and will reduce its efectiveness. Tis proce- dure (solution) will not damage CS. Inhibitor efectiveness should be tested prior to cleaning, and the iron content should be measured during cleaning. A corrosion coupon can even be placed and monitored inside the circulation unit. Inhibitors for wet CO 2 pipeline service Q: What are the common inhibitors used in wet carbon dioxide (CO 2 ) pipelines with minimum contaminants? A: Tese are aliphatic amines, water or oil soluble, depending on the purpose. Tey form a monomolecular and dynamic flm against contaminants. Tere are diferent formulas, with or without neutralizer. A: Internal corrosion control of wet CO 2 with inhibitors has been very successful. Selection of the inhibitor can be done in the laboratory with a number of tools. Tese include the conventional "coke" bottle test, rotating cylinder, jar test, etc. Tese tests use weight loss or corrosion probes to determine corrosion rate with various inhibitors and variable chemical dosages. You can use actual feld fuids or synthetic fuids to do the test. Te fuid can be sparged with CO 2 to mimic feld pH as well. Pigging the line will also help if you have bacteria-induced corrosion or underdeposit corrosion. Examine the pig solids for composition. Test the con- densed water for corrosion products and inhibitor residual, as well as bacteria. The major chemical companies have the equipment and knowledge to select the right inhibitor. I always request that the chemical company qualif y the inhibi- tor based on this ty pe of testing. I do not recommend selecting an inhibitor based on case histories or word of mouth. Corrosion inhibitor chemistry in- cludes polyamines, imidazoline, fatty

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