Materials Performance

APR 2017

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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11 NACE INTERNATIONAL: VOL. 56, NO. 4 MATERIALS PERFORMANCE APRIL 2017 THE BLOG Continued on page 13 The following are excerpts f rom the NACE International Corrosion Net work (NCN) and NACE Coatings Net work . These are email-based discussion g roups for corrosion 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 Please be advised that the items are not peer-reviewed , and opinions and sug gestions are entirely those of the inquirers and respondents .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. Replacing Coal Tar Epoxy Q: We used coal tar epoxy in an immersion (tank) application, with a saline acidic and some saline basic environment. We also have an external application with saline acid splash. Does anyone have experience in replacing coal tar epoxy with other ty pes of coatings? A: Surface preparation is simple and straightforward: see NACE Stan- dards No. 1 and 2 for immersion and NACE No. 3 for splash and spillage. Verif y the application's profile depth and shape, verif y that the application is free from hy- drocarbons (grease and oil) contamina- tion, and ensure that soluble salts are not >10 ppm. Be certain that a NACE-certified Coating Inspector is involved. Coating selection should be based on the service environment—chemicals, concentration, and temperature. As chemical concentration and temperature exposure increase, move from polyamide epoxy to polyamine-cured phenolic epoxy, and f inally, novalac epoxy. A ll have reasonable application pot life and recoat window opportunities. A ll can be applied with single-leg airless spray equipment. A lternative coatings, such as aromatic poly urethane, poly urea, and plural- component epoxy, are available but require a much higher level of applicator sophistication to achieve success. A: We had the same situation. We replaced coal tar epoxy with im- mersion-ty pe epoxy mastics and solvent- free coatings based on the chemical resis- tance of the coating to the environment specified in the project. Zinc on Stainless Steel Q: Why have inorganic zinc (IOZ) silicate primers not been applied on stainless steel (SS)? Zinc will sacrif ice itself to the SS. What is the recommended remedy if IOZ silicate/epoxy zinc-rich

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