1. A METHOD FOR PRODUCING VITREOUS ENAMEL COATINGS ON ALUMINUM METAL WHICH COMPRISES TREATING THE ALUMINUM METAL IN AN AQUEOUS ACID SOLUTION CONTAINING FLUORIDE IONS AND NITRIC ACID IN CONCENTRATIONS EQUIVALENT TO FROM ABOUT 0.5 TO 25 GRAMS PER LITER OF AMMONIUM FLUORIDE AND FROM ABOUT 1.3 TO 106 CC. PER LITER OF AN AQUEOUS NITRIC ACID SOLUTION CONTAINING 70% HNO3 BY WEIGHT AND THEREAFTER ENAMELING THE ALUMINUM WITH AVITREOUSENAMEL.

9. A METHOD OF COATING ALUMINUM WITH VITREOUS ENAMEL WHICH COMPRISES ELECTRO-CHEMICALLAY PRODUCING AN ANODIC ALUMINUM OXIDE FILM HAVING A THICKNESS OF FROM ABOUT 0.0002 TO ABOUT 0.00005 INCH ON SAID ALUMINUM, DIRECTLY COATING AT LEAST A PORTION OF SAID FILM WITH A FUSIBLE VITREOUS MATERIAL, AND HEATING THE COATED FILM TO AT LEAST THE FUSION TEMPERATURE OF SAID VITREOUS MATERIAL.