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49 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 Continued f rom page 47 n NEW Faster measurement speed— 60+ readings per minute n N o calibrat ion adjustment required for most applicat ions – measure right out of the box! n Tough probes, robust housing and strong two year warranty n All models include Certificate of Calibration n Includes PosiSoft suite of software f or viewing and reporting dat a Co at in g Th ic k n e ss Gage s Simple. Durable. Accurate. DeFelsko Corporation l Ogdensburg, New York USA Tel: +1-315-393-4450 l Email: techsale@defelsko.com Award Winning Compatibility! The PosiTector gage accepts ALL coating thickness, surface profile, environmental, soluble salt, Shore hardness and ultrasonic wall thickness probes. 1 -8 0 0 -4 4 8-3835 www. d ef el sko. com Scan Modes Advanced models now include 3 Powerful Scan Modes NEW! For an initial evaluation of the coating and corrosion behavior of a NPE-ZRP, the authors implemented short-term testing to identify important coating characteristics and electrochemical parameters that could affect the coating system's overall durability. e NPE-ZRP was applied over A36 (UNS K02600) carbon steel coupons with coating thicknesses ranging between 150 and 300 µm. Testing was comprised of four months of outdoor exposure to a harsh marine envi- ronment and 60 days of water immersion in a sodium chloride (NaCl) solution. e outdoor exposure tests subjected the NPE-ZRP coated samples to environments at a beach test site in the Florida Keys and an inland test site ~16 km (10 miles) from the South Florida coast. Before testing, a 25.4- mm long and 0.5-mm wide scratch was made on one set of samples so the effect of local coating damage could be determined. A crevice environment was simulated on another set of samples by placing an acrylic plate over the coupon surface to create a crevice that was exposed to air and moisture. e coated samples were then mounted on a south-facing exposure rack and oriented at a 45-degree angle toward the horizon, and exposed from April 22 to August 22, 2016. During exposure in the summer months, the temperature highs were typically between 80 to 95 °F (27 to 35 °C) with relative humid- ity sometimes >90%. Cumulative rainfall was ~250 mm for the beach site and ~500 mm for the inland site. Exposure to ultraviolet light was relatively high at both test sites during the exposure period. e solution immersion tests, per- formed to simulate runoff and pooled drainage water, immersed the NPE-ZRP coated steel coupons in a 3.5 wt% (0.6 M) NaCl aqueous solution for 60 days. Corro- sion testing included open-circuit potential and linear polarization resistance measure- ments. Activated titanium was used for the counter and reference electrodes for each test cell. After testing, the authors observed sur- face discoloration for the samples in all exposures—from a dark grey color to a whitish appearance that was thought to be related to zinc corrosion products caused by exposure to the high relative humidity and rainfall exposure outdoors, and solu- tion immersion in the laboratory. Signifi- cant coating deterioration, such as rusting, blistering, and cracking, however, was not evident for samples in either the outdoor or immersion tests. Comparatively higher coating bond strength was identified for all exposures, and barrier protection was observed. No significant changes in coating thickness were measured. Although the intact coating samples showed good corrosion protection follow- ing exposure, moderate surface rust was observed on the scribed samples. After an initial period of high corrosion activity, con- sumption of the exposed zinc at the scribed region continued at a slow rate without Continued on page 51