Brightening aluminum and aluminum alloy surfaces

Claim 1

THE PROCESS OF PRODUCING A PERMANENTLY HIGHLY REFLECTIVE SURFACE ON ARTICLES FORMED OF ALUMINUM AND ALUMINUM ALLOYS COMPRISING THE STEPS OF DEGREASING THE ARTICLE; WASHING THE DEGREASED ARTICLE; IMMERSING THE ARTICLE IN A HIGHLY ACID AQUEOUS BATH ESSENTIALLY CONSISTING OF 30% TO 35% PHORPHORIC ACID AND 10% TO 15% CHROMIC ACID SO AS TO CLEAN THE ARTICLE BY REMOVING ALUMINA THEREFROM WITHOUT ATTACKING THE ALUMINUM METAL, THEREBY PRODUCING A SATIN-LIKE SURFACE ON THE WASHED ARTICLE; ELECTROLYZING THE SATIN-LIKE SURFACED ARTICLE IN AN AQUEOUS ALKALINE BATH CONSISTING ESSENTIALY OF AN ALKALI METAL PHOSPHATE AND AN ALKALI METAL ALUMINATE IN AN AMOUNT SUCH THAT SAID BATH CONTAINS BETWEEN 2% TO 10% PHOSPHATE IONS AND BETWEEN 0.5% TO 5% ALUMINATE IONS SO AS TO PRODUCE A THIN COATING OF ALUMINUM HYDROXIDE ON A SURFACE OF THE ARTICLE, THEREBY BRIGHTENING THE SAME, THE ALUMINUM ARTICLE BEING THE ANODE IN THE ELECTROLYTIC CELL; WASHING THE THUS COATED ARTICLE; SUBJECTING THE THUS COATED AND WASHED ARTICLE TO A HIGHLY ACID AQUEOUS BATH ESSENTIALLY CONSISTING OF PHOSPHORIC ACID AND CHROMIC ACID SO AS TO DISSOLVE ALUMINA ON THE SURFACE OF THE ARTICLE, THEREBY FURTHER AND EVENLY BRIGHTENING THE COATED SURFACE OF THE ALUMINUM ARTICLE; AND WASHING THE THUS TREATED ARTICLE SO AS TO RECOVER THE FINAL PERMANENTLY BRIGHTENED ALUMINUM ARTICLE.