Quaternary ammonium bicarbonates are suitable for use as catalysts in curable epoxy compositions. The curable compositions prepared therewith are used to prepare coated substrates, and to produce conformally sealed printed wiring boards and flexible circuits. Methods for preparation and curing are also provided. Of particular utility are compositions comprising benzytrimethyl ammonium bicarbonate. The curable composition is coated onto a first film or sheet, including a polyimide film or sheet. The coated sheet is then contacted to the surface of second film or sheet, where preferably there are discrete metallic conductive pathways disposed thereupon.