Sealing foam insulation in dry kilns

The corrosion of the aluminum skin of package dry kilns is a major problem to the wood drying industry. Much of this corrosion is caused by the uptake of moisture and weak acids by the foam or fiberglass insulation within the kiln wall panel. The absorbed moisture and acid in the kiln insulation keeps the aluminum skin wetted so that corrosion occurs from the inside of the kiln wall. A test chamber was developed to allow the accelerated testing of insulation sealing methods and materials. A screening test of 21 coating or sealing methods was conducted on 10- by 10- by 5.1-cm-thick blocks of a rigid, polyisocyanurate foam. Three sealing methods were selected based on their superior performance in the screening test. Sealing the foam with two coats of coal-tar epoxy paint, wrapping the foam with polyethylene plastic, and sealing the foam with aluminum tape all provided significant protection from moisture uptake in the accelerated tests.

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