Materials Performance

NOV 2014

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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57 NACE INTERNATIONAL: VOL. 53, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2014 systems. Luckily for us, the corrosion failure rates are something we can toler- ate. Nonmetallic piping kills two birds with one stone if you also have buried systems. Tis eliminates the need for cathodic protection as well as a corrosion inhibitor Q: What is the best inhibitor to protect the outer surface of carbon steel after hot rolling or forging? The oxide layer can't protect it in the wet environment of the atmosphere. A: Ty pical inhibitors applied to the surface will not protect the steel very well, especially in wet environments. A low-cost shop primer is usually applied to structural steel for mild environments and short-term protection. If you are worried about appearance you can apply fnish coats at a later date. If not, we usually left the shop primer on and forgot about it. If you want to protect it from severe corrosion for an appreciable length of time, a heav y-duty coating system appropriate for the application is called for. For steel that will be transported and installed at some distance, you might consider a frst coat of inorganic zinc (IOZ) over a commercial-blasted surface. After installation, any damage can be repaired and epoxy and/or poly urethane topcoats can be applied. Te IOZ is better at resisting damage than most coatings. Sulfuric acid passivity Q: Can phosphoric acid (H 3 PO 4 ) be used in an 80% sulfuric acid (H 2 SO 4 ) water mix to passivate the mix, similar to using nitric acid (HNO 3 ) for this purpose? If yes, what level of H 3 PO 4 would be needed? A: Defnitely not! Te H 3 PO 4 lacks oxidizing capacity and would be displaced by H 2 SO 4 . Read MP Online NACE International members have free access to MP Online, with back issues to 2005. Visit MP Online in the Publications area of the NACE Web site:

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