Inorganic Surface Treatments for Weather-Resistant Natural Finishes.

Abstract : Treating wood surfaces with aqueous solutions of inorganic chemicals by simple brush applications can: retard degradation of the surfaces by ultraviolet irradiation; enhance effective use of polymer coatings transparent to UV; reduce the swelling of wood by water; impart a degree of fungal resistance to the surface and surface coatings; serve adequately as natural exterior finishes. Effective treatments were ammonium chromate, ammonium copper-chromate, ammonium copper-chrome-arsenate, cupriethylene diamine, copper molybdate, and copper ferricyanide. Chromate treatment improved performance on wood of oil and latex stains, linseed oil-based paint, clear latex coatings, and oil-base varnishes. Water-soluble extractives in redwood and redcedar were fixed by treating the wood surface with dilute solutions of copper and chromium salts. The investigation also involved erosion of treated and untreated wood surfaces by leaching and UV irradiation in accelerated weathering. A procedure was developed for quantitatively measuring these effects. A promising method of improving the fungal resistance, color, and permanence of acid-copper-chromate treatments with resorcinol is also reported. (Modified author abstract)