Low VOC Barrier Coating for Industrial Maintenance
Cost and performance rept.
ENVIRONMENTAL SECURITY TECHNOLOGY CERTIFICATION PROGRAM ALEXANDRIA VA
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The objectives of this demonstration are to 1 provide a full-scale validation of the low volatile organic compound VOC barrier coating LVBC for use as an architectural and industrial maintenance AIM coating, 2 assist in the transition of a nonaircraft topcoating using the zero- VOC topcoat ZVT MIL-PRF-85285D, Type III, Class W, and 3 enable the transition of this very low VOC AIM coating system directly into the hands of U.S. Department of Defense DoD end users who require aboveground storage tank AST maintenance painting. Corrosion of AST steel exterior surfaces is a perennial and costly problem. To protect against corrosion, AST exterior surfaces typically receive a three-coat system consisting of the following 1 A zinc-rich epoxy primer Military Detail Standard MIL-DTL-24441, Formula 159, Type III 2 An epoxy intermediate MIL-DTL-24441, Formula 152, Type IV and 3 A polyurethane topcoat Military Performance Standard MIL-PRF-85285D, Type II. These coats are commonly formulated with about 304 grams per liter gl 2.5 pounds per gallon lbsgal, 340 gl 2.8 lbsgal and 340 gl 2.8 lbsgal of VOCs, respectively. Exterior AST maintenance painting is often required at around 8 to 10 years of service. However, the original three-coat system described above is not appropriate for use over aged and weathered coatings. When the original system has been used as an overcoat system, it has contributed to costly premature coating failures. These overcoat failures typically occur as a result of high levels of residual cure stress curing of the overcoat system combined with the daily thermal cycling daily temperature extremes. Therefore, typical maintenance consists of making spot repairs to visibly corroded areas or waiting until the existing coating is fully removed and a reapplication is necessary.
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