Laboratory tests were conducted to assess the ability of a 3-mil thick adhesive-backed polyethylene film (Polymask) to protect vehicle paint finishes from acid-rain damage. The laboratory tests employed conditions known to be relevant to actual service conditions including: 1) automotive paints of various colors, 2) simulated acid-rain solutions (of pH values from 2.2 to 5.5), and 3) service temperatures (120 to 160 °F). Laboratory tests included cyclic evaporation and soak tests similar to those employed in a previous series of tests for Toyota (1). Cyclic evaporation tests were performed for 12 cycles and the soak tests were performed for 5 days. Two types of tests were performed: 1) permeability tests to determine the ability of acid rain to damage automotive paints through the protective coating and 2) edge tests to determine the effect of acid rain along the edge (seam) between the unprotected paint and the polyethylene film.

The permeability tests revealed that the film provided excellent resistance to permeability damage. The level of protection was superior to the acrylic polymer transit coating previously tested. However, the edges were sites of elevated damage which was more severe than for the exposed paint. Some undercutting was detected under the film. The undercutting was not prevalent at lower test temperatures and higher acid rain pH values. The edge damage might be prevented by careful placement of the seams or by caulking along the edges.

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