Materials Performance

NOV 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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18 NOVEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 11 MATERIAL MATTERS Continued f rom page 17 The portable infrared curing instrument encloses a 24-in (610-mm) diameter cylindrical substrate. Photo courtesy of Ovante. In November 2011, the EPC was sub- jected to two 13-month tests by A LDOT that exposed EPC-coated highway sign- posts to the coastal marine environment of the Gulf of Mexico—direct sunlight, seawater, and salt-laden air. The interior and exterior of two 14-ft (4.3-m) long, 2.5-in (64-mm) square, 10-gauge galva- nized steel signposts, with 11-mm diam- eter perforations spaced 1 in (25 mm) apart on center, were coated with EPC and delivered to the A LDOT 9th Division off ice in Mobile. One EPC-coated signpost was installed next to an uncoated galva- nized signpost on the side of State Route 182, an A labama coastal highway that connects Gulf Shores and Orange Beach. The other EPC-coated signpost, along with an uncoated galvanized signpost, was bolted to the wooden pilings of a wooden pier in the Perdido Bay next to the Perdido Pass Bridge in Orange Beach. In the bay, ~7 ft (2.1 m) of the signposts were submerged in seawater, with an additional 2 to 3 ft (0.6 to 0.9 m) in the splash zone and the remainder in the atmosphere. The two signposts in the bay were also exposed to marine-grade pres- sure-treatment chemicals from the wooden pier, as well as marine life. After six months, the EPC-coated signpost was removed, a 6-in (152-mm) section was cut from the submerged end, and it was placed back onto the piling with the newly exposed steel edge in the seawater. At the end of the test, the EPC coating on both signposts was still intact. On the signpost submerged in the bay, the EPC coating in the splash zone was undam- aged from repeated splashing and drying. The EPC coating on the portion of the post submerged in the bay was also undamaged—crustaceans and plant life had not penetrated the coating and were easily scraped off. On the exposed steel edge that was submerged for the latter seven months of the test, there was a small amount of surface rust where the coating had been damaged by the saw used to make the cut. The performance tests indicated to the developers that the EPC would pro- tect galvanized steel in a marine environ- ment; but it would be diff icult to apply the heat-cured EPC to a steel pole, lattice tower, or other components in situ. To address this technolog y gap, they devel- oped an infrared curing instrument that is portable and can cure the EPC in the f ield. The resins in the EPC react favor- ably to infrared energ y; and when exposed to infrared wavelengths between 3.5 to 9.5 µm, they swell and absorb the plasticizer and also merge with adjacent swelling resins to form a nonporous skin on the substrate. The portable curing instrument is comprised of a ring of infra- red generators that produce infrared wavelengths between 3 and 10 µm. The instrument is modular in design and can be assembled to f it around various sizes of round or square structures such as poles and beams. It encloses the portion of the coated substrate to be cured with the heat generators facing inward toward the coated substrate, and is constructed to utilize its own ref lective surfaces and the shape of the structure being coated to maximize the effect of the infrared energ y being generated. The instrument preheats the sub- strate until it is hot enough for the coat- ing to adhere, then the drive mechanism moves the heater up or down to expose the preheated substrate so the liquid coating can be spray-applied. Once the substrate is coated, the drive mechanism moves the heater over the coating to cure it. When the coating is cured, the drive mechanism moves the heater to an adja- cent, uncoated portion of the substrate and preheats it. Then the coating applica- tion and curing process are repeated until the entire substrate is coated and cured. A lthough the ring is open at the top and bottom, the heat is contained within the f ield of application and very little escapes. Brasher notes that a ~16-ft (4.8-m) length can be coated at one time. The portable infrared curing instru- ment's drive system runs on a 12-V power supply (e.g., an automotive battery), and the heating element is fueled by liquef ied petroleum gas (LPG). It reaches the cur- ing temperature in ~1.5 min and the coat- ing cures in ~4 to 6 min depending on the thickness of the coating, which can be applied in thicknesses ranging from 37 to 375 mils (0.9 to 9.5 mm). The curing instrument can be adjusted to cure

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