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37 NACE INTERNATIONAL: VOL. 55, NO. 12 MATERIALS PERFORMANCE DECEMBER 2016 Improving Inorganic Zinc Coatings with Mineral Fiber Reinforcement In highly corrosive environments, both organic and inorganic zinc-rich primer coatings are used extensively as part of a high-performance coating system. Because of their excellent cathodic protection attri- butes, inorganic zinc (IOZ) primers are preferred for coastal and offshore environ- ments. Although they have performance advantages for corrosion protection, IOZ primers do possess some application limitations. For zinc primers to be effectively anodic, the zinc particles must be electrically con- nected with each other and the steel sub- strate, so IOZs are often formulated with high zinc loads and pigment volume con- centrations near the point where the binder quantity is just enough to wet the pigment. To improve zinc packing or particle-to- particle contact, coating formulators often use varying sizes of zinc particles. While this particle size optimization and distribu- tion benefits the coating, the film's charac- teristics may be unfavorable and result in low cohesive film strength (i.e., low adhe- sion values), a high possibility of mudcrack- ing, and high viscosity. IOZs are typically specified either as a single coat system at 100-µm dry film thickness (DFT) or a 50-µm primer to be overcoated with a barrier coat- ing. However, IOZ film thicknesses are often much higher on complex structures, which results in areas with too much coating. Additionally, IOZs have limited application windows in which they can be successfully applied, they cure slowly, and require humidity to cure. Two of the most common failure mech- anisms seen in IOZs are mudcracking caused by excessive film build and topcoat delamination caused by insufficient curing COATINGS & LININGS ESSENTIALS Continued on page 38 Shore Hardness Durometer 1 -800-448-3835 l www. defelsko.com D eFelsko Corporation l O gdensburg, N ew Yor k USA Tel: +1-315-393-4450 l Email: techsale@defelsko.com Measures the hardness of non-metallic materials. Two models are available - Shore A and Shore D N EW n U ser-adjustable measurement time with onscreen countdown n Aut o Ignor e mode disregards readings below 20 or above 90 n Int er nal memory, st at ist ics and USB port n Includes PosiSoft suite of software for viewing and reporting data n Advanced models connect to iOS or Android Smar t devices n C onf or ms to nat ional and internat ional standards n Certificate of Calibration showing traceability to NIST included