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High-build plural-component polyurea-hybrid spray-on coatings quickly and cost-effectively rehabilitate metal roof. A badly degraded aluminum alloy roof at an Army airfield was chosen for rehabilitation. The polyurea-hybrid coating was economical to apply, and is expected to extend the service life of the metal roof by providing a very tough moisture impermeable spray-on membrane. It effectively seals surface defects, even around penetrations, pinholes, and seams.
Wheeler Army Airfield, near Honolulu, Hawaii, experiences severe corrosion problems on metal roofs from exposure to high humidity, and alternating rain and sunlight. Several metal roofs have degraded and received roofing condition ratings of 20 to 50 (on a scale of 1 to 100, with 100 being new). The factory-coated standing seam metal roof panels were also degrading because, of high ultraviolet (UV) light exposure.
Over the past decade, problems with corrosion of metal roofs and degradation of metal roof coatings have been addressed by researchers at the U.S. Army Engineer Research & Development Center (ERDC), Construction Engineering Research Laboratory (CERL).14 The objective of this project was to evaluate an innovative roofing restoration technique that utilizes a sprayable elastomeric membrane coating applied over an existing deteriorated metal roof coating. The new coating had to meet aesthetic, color, and other requirements. The ease of application, cost effectiveness, and functionality of this innovative coating technology in a severely corrosive atmosphere was evaluated.
Polyurea-Hybrid Roof Elastomer Coatings
There are a number of commercially available sprayable membrane-producing coatings from the polyurea families that have the potential for roof rehabilitation. The coating chosen was a pluralcomponent polyurea hybrid that could be applied over an existing deteriorated roof, economically providing a new moistureproof membrane that would significantly extend the service life of the roof by a minimum of 1 5 years.
The coating materials selected were VFT0MT primer and the VFFM-SSo+ two-component polyurea-hybrid topcoat. Both primer and topcoat were comprised of two components: (A) polyisocyanate pre-polymer and (B) resin blend formulation. The topcoat material contained a copper pigment that gives the appearance of a metallic coating when properly applied. The pluralcomponent polyurea-hybrid coating material was 98% solids and met the ASTM criteria for tensile strength, elongation, and permanent set (ASTM D4I25"6), as well as hardness (ASTM D22407), tear resistance (ASTM D624"), and water vapor permeability (ASTAi...