Holidays | coating inspection
important to avoid any electrical shocks. Solutions for dealing with detected holidays are
completely dependent upon the nature of the fault detected and the coating specification, which will determine whether the coating can be renewed or not. If the lining is already at the maximum coating thick- ness, for instance, then another coating cannot simply be applied on top of the existing holiday. In such cases, the area around the discontinuity must be initially delineated with the edges feathered in towards the defect. Once this is completed, the area can be frost- blasted prior to application of a replacement coating. In cases where the coating is under the maximum thickness, then another coating can be applied directly and, by simply roughening the surface prior to a succes- sive application, the holiday can be covered and successfully eliminated. After any coating repair is completed, another
holiday test must be conducted in order to establish that the repair has been successful. It is strongly advised that only the area of repair is tested in order to prevent excessive stress being applied to the coating’s integrity.
About the authors: Ian Wade is a coating inspector at Belzona Polymerics; Thomas Belli is marketing specialist. Established in 1952 in the UK, Belzona is a designer and manufacturer of repair composite materials and industrial coatings for a wide range of applications, including oil&gas infrastruc- ture. The company has offices in Europe, North America and Asia and distributors in more than 120 countries. ❙
www.belzona.com
Above: Typical low-voltage testing
equipment for pinhole
detection
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