CoatingsPro Magazine

JUL 2013

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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Page 71 of 86

Near-White Blast Cleaning on the exterior of more than 3,000 lineal feet (914 m) of new 8-, 10-, and 12-inch (20, 25, and 31 cm) pipe and more than 200 fittings at the contractor's blast facility. A properly calibrated surface profile gauge was routinely used to verify that the coating manufacturer's optimum surface profile of 1 to 2 mils (25–51 microns) was met. Perfect Painters used a synthetic abrasive known to be a proven performer on new steel surfaces and mil scale. The base primer technical data sheet specified minimal surface preparation per NACE No. 3/SSPC-SP-6: Commercial Blast Cleaning. In practice, all of the mil scale had to be removed prior to coating installations, thereby rendering a NACE No. 2/SSPC-SP-10: Near-White Blast Cleaning. Perfect Painters followed the better surface preparation advice in order to provide its client with better performance. After the abrasive cleaning was complete each day, the crew used compressed air to blow down the prepared steel. This was done in order to ensure a dust-free surface. Then, Perfect Painters applied a coat of polyamide epoxy steel primer to the manufacturerrecommended spread rate of 2 to 4 mils (51–102 microns) dry film thickness (DFT). In addition to corrosion inhibitors, the primer they used promoted ease of application. Ben's crew then applied an intermediate coat of a high-solids polyamide epoxy on the previously primed surfaces. The intermediate coat featured high build and ease of application characteristics. The recoat window of up to one year gave both the facility's owner and Perfect Painters peace of mind to know they had a wide window in case any problems occurred (e.g., site delays due to installation). Offsite surface preparation and installation of prime coats provided several benefits to both the client and coatings contractor. First, abrasive blasting in environmentally sensitive areas provides the challenges and expense of containment. There are additional costs associated with disposal of spent abrasive at hard-to-reach worksites. Second, the weather was not a factor in productivity, enabling the parties to avoid weather delay costs. Third, the increased costs of Above The t wo-man coatings crew worked in tandem: one technician completed the surface prep and applied the base coat while the other technician followed with the intermediate and finish coats. of water and biodegradable salt remover and degreaser additive on all pipes and fittings. To clean the inaccessible surfaces, the landing zones for the pipe support stands required the pipe to be lifted 1 to 2 inches (3‒5 cm) off the stands. The final step in surface preparation was to complete spot touchups of the washed surfaces per SSPC-SP-1: Solvent Cleaning, The recoat window of up to one year gave both the facility's owner and contractor peace of mind to know they had a wide window in case any problems occurred. mobilization of heavy equipment and aggregate materials to a remote location were not a factor. Lastly, there were no extra expenses associated with delays caused during the installation process. After installation, Perfect Painters mobilized for phase two of the project. The field specification called for pressure cleaning at a max of 2,500 psi (17,237 kPa). The crew utilized a mixture Left The job did not include abrasiveblasting on site, bad weather, mobilization of equipment, or instillation delays. So what could have caused the coatings problem? SSPC-SP-2: Hand Tool Cleaning, and SSPC-SP-3: Power Tool Cleaning of welds, scratches, and rust areas. When ready, the crew applied a spot coat of shop primer on the spot-prepared surfaces. Then, the entire pipeline was painted using a polyester modified, aliphatic, acrylic polyurethane finish coat with less than 300 g/L (0.8 lb/gal) of volatile organic compounds (VOC). This topcoat exhibited color and gloss retention in exterior exposures and had excellent application properties. Brush- and rollerapplication of the finish coat at 3 to 4 mils (76–102 microns) DFT prevented July 2013 g 69

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