CoatingsPro Magazine

MAY 2017

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 56 of 84

56 MAY 2017 COATINGSPROMAG.COM below. To safeguard the crew, management was sure to have them wear hardhats, harnesses, safety vests, double lanyards, respirators, and blast hoods as required. To reach the specified NACE No. 2/Society for Protective Coatings (SSPC) Surface Preparation (SP) 10: Near-White Metal Blast Cleaning, the two, eight-man blast crews used #8 tips to fire W Abrasives' 60/40 steel shot at the existing coatings system. Going was slow. e bridge's last coating system was sprayed over an even older coating system. In addition to fighting decades-old coatings totaling 45 mils (1,143.0 microns) or more in places, the blast crews uncovered more rust than anticipated — much more! "In places, we were blasting sections that had two previ- ously known steel repairs to make and our blast crews would reveal 20 more," said Forakis. e extra welding wreaked havoc on Titan's original scaffolding system plan. "We typically move decks one section at a time to leapfrog," said Forakis. "As soon as we finish a section, the night crew just grabs those decking panels and moves them ahead. at way, we don't tie up thousands of square feet of decking material. Unfortunately, that's not how it worked out. You want to move it, you're ready to move it, but the steel guys are still back there. We practically rigged the entire structure from front to back with decking and scaffolding. Our initial plan of leapfrogging went down the tubes." But that wasn't the worst of their worries! "One huge challenge was blasting core box [think box beams] corners," said Titan Foreman/Superintendent Dale Patoska. "Some had been previously packed with epoxy resin caulk, but the ones with soft urethane caulk were an even bigger pain! With hundreds of caulked corners, our only option was to resort to hand tools to get that stuff out of there. We tried greenhorns at first but quickly found out they didn't have the technique or could even recognize what finished hand prep needs to look like. e only way to keep from falling behind was to assign extra men from the blast crew." Trigger Happy As soon as paint debris and spent abrasives were vacuumed and deposited into hazardous waste dumpsters, the Titan paint crews sprang into action. W hile some crewmen mixed the Sherwin-Williams Zinc Clad III HS three-component polyam- ide epoxy primer, others readied 64/1 WIWA airless spray pumps armed with #319 tips. Specifications called for 5‒6 mils (127.0‒152.4 microns) in one pass. is is one application where it paid to be a bit trigger happy. "We did the core box corners first, and by the time you're done, you only have a small amount of flat surface to coat," said Patoska. "ere weren't many flat areas on this bridge." e coatings crews also demonstrated a light touch on the core box corners. ey were mist-coated because specs called for the application of Sherwin-Williams Macropoxy 920 penetrating epoxy primer. e two-component sealer is designed to penetrate any tightly adhered rust and may be used over zinc-rich coatings. Sherwin-Williams recommends using low-speed mechan- ical agitation to mix Macropoxy 920 Part A and Part B separately. One Part B is added to three Parts A and agitated for at least five minutes. en things get hot! Up top, the crew pre s sure wa shed the susp ension cable s b efore applying t wo coats of Rust- Oleum Nox yde at 7-9 mils (17 7.8-228.6 microns) each and then a topcoat of their 3700 DTM at 1.5-2.5 mil (38.1-63.5 microns). Bridge Coatings Sur face p rep in clu d e d ab ra si ve bla s ting to achieve NACE No. 2 / Society for Protective Coatings (SSPC) Surface Preparation (SP) 10: Near-White Metal Bla st Cleaning. They used hand tools to remove caulking on the 100+ core box corners. Containment wa s al s o required on this projec t, e sp ecially a s the crew worked with minimal vehicle lane closures. Abrasive blasting and spray application of the painting needed to occur in a contained environment.

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