CoatingsPro Magazine

JUL 2016

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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54 JULY 2016 COATINGSPROMAG.COM Never Again Photo 1. The single, isolated pinhole. The Case of the Pinholes: To Fix or Not to Fix By D. Terr y Greenfield, Principal Consultant with CorroMetrics Services, Inc. M ost specifcations include a statement such as, "Ensure each coat is free of pinholes, blisters, and holidays, and avoid skips, runs, sags, and drips. Applied coatings shall form a continuous flm." W hat does that actually mean? At face value, it means just what it says: "Free of pinholes..." Tere should be no pinholes in the coating. But what happens when the coatings inspector has to inform the project team that there are pinholes all over the surface, and it's going to have to be repaired? Consider the intended use of the installed system when looking at pinholes in the coating flm. In some instances, it may be reason- able to accept some pinholes in the coated surface. Some Background If the coating system is to be used as a lining, then it obviously should be a continuous flm and free of any defect (such as a pinhole) that would allow exposure of the substrate to the material contained in the vessel. Te lining would be used to help protect a steel tank from the potable water inside, for example. Te continuous lining is crucial in that case. To ensure a 100 percent contin- uous flm that is pinhole-free in an immersion environment, such as a tank, testing is typically performed with either low- or high-voltage holiday testing equipment. Testing is performed, non-conforming locations are identifed for repair, and after the repair is executed, the location is re-tested to ensure that it's part of a 100 percent defect-free (pinhole or Photos courtesy of the author Consider the intended use of the installed system when looking at pinholes in the coating film. In some instances, it may be reasonable to accept some pinholes in the coated surface.

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