CoatingsPro Magazine

NOV 2018

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 63 of 76

COATINGSPRO NOVEMBER 2018 63 T his way, the shipyard would be able to "sk ip" apply ing the pr imer that the manufactur ing company intended to be used w ith the water-bor ne intumescent paint and thus apply the intumescent directly on the zinc coating. T he intumescent was then to be covered in a topcoat. e coating manufacturer of the zinc-rich epoxy coating was di•erent than the manufacturer of the intumes- cent and topcoats. Application of Coats According to the speci•cation provided by the shipyard, the process was that: 1. The surface preparation was completed to achieve grade Sa 2½; 2. The zinc primer was applied to a dry film thickness (DFT) of 40–60 microns (1.6–2.4 mils); 3. The intumescent coating was built up to 2.5 mm (0.1 inch, or 2,540 microns) DFT. is procedure took more than one-step coating as the maximum application according to the data sheet is 1,000 microns (39.4 mils) wet. To achieve the DFT, four to •ve di•erent coating steps were made. Each of them resulted in an average of 430 microns (16.9 mils). 4. The topcoat was applied to a WFT of 80–100 microns (3.1–3.9 mils). T he topcoat manufacturer had agreed in writing to the primer change and sent literature proving that both products and this particular system did work under laborator y conditions w ithout any problems, thus provid- ing the shipyard w ith confidence to apply the intumescent paint on top of the zinc coating. T he lab tests were conducted under special enclosed conditions at ambient temperatures and on test plates that were 30 cm by 30 cm (11.8 inches x 11.8 inches). Often, paint manufacturers apply their coating over other manufactur- ers' coatings that have been previously applied, and years go by w ithout having any problems. T hat was not the case here. Responsibilities & Legality e shipyard was responsible to deliver the product to the buyer. e coating sub-contracted company was responsible for the paint purchase and application. e coating manufacturer of the zinc primer was responsible for the delivery and guarantee of the paint. e intumescent and topcoat manufacturer was responsible for that and subsequently also for con•rming in writing that the "changed " coating system worked with the new zinc primer coating. In legal terms, there were signed contracts between the shipyard and coating contractor but not between the shipyard and the paint manufacturers. e shipyard, in this case, was responsible for the 18-month delay in establishing a re-coating schedule. Investigation Research At least four expert investigation reports were presented by third-party surveyors and experts to the shipyard. e subcontractor had also presented di•erent third-party surveyor and experts reports to the shipyard. Unfortunately, these reports were more or less ignored by the yard. Included in the research were 90–120 dolly tests, which were conducted in di•erent areas of the ship. e results varied. Some showed a failure in between the coating layers, but some did not, and the pull-o• tests showed a range of MPas that did not allow for proper evaluation as to where the actual division within the coating failure occurred (i.e., between the zinc and the intumescent or between the layers of the intumescents). e results were inconclusive. Many di•erent samples were taken from the ship for a microscopic analy- sis. Di•erent test samples were also analyzed with digital micrometers. e microscopic analyses were done on test samples that had fallen o• the substrate. e o›cial cut-out tests were not presented in any of the reports that came out, putting even more in question the veracity of all other reports. ere are also written statements from the manufacturer of the zinc primer that put in doubt whether or not the applied water-borne intumescent paint would " hold on" to their coating, and that a possible saponi•cation of the water-borne coat (aka release of fatty acids) would loosen the adherence between the coats. Another report, provided by the intumescent coating manufacturer, stated that they also responded with a "possible" coating failure in between coatings due to a "possible" saponi•ca- tion created by the intake of moisture through the intumescent coating reach- ing the zinc layer and thus producing a Dolly tests showed that the cause of the failure was not due to the adhesiveness between the zinc primer and the substrate but between the zinc and the intumescent coating. Bulkhead Delamination

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