Process of anodizing

Claim 1

IN THE ART OF ANIDIZING ALUMINUM, THE METHOD COMPRISING THE STEPS OF: (A) FORMING A UNIFORM, DENSE AND ELECTRICALLY-RESISTIVE OXIDE LAYER ON THE SURFACE OF AN ALUMINUM ARTICLE BY IMMERSING SAID ARTICLE IN AN ACIDIC DISSOLVING ELECTROKYTE, APPLYING AN ELECTRIC CURRENT TO THE ALUMINUM AS ANODE AT AN AVERAGE ANODIZING CURRENT DENSITY NOT IN EXCESS OF 100 AMPERES PER SQ.FT., EMPLOYING AN INITIAL CURRENT DENSITY IN THE RANGE OF 20 TO 600 AMPERES PER SQ.FT. AND CONTROLLING THE ANODIZING RATE TO PREVENT BURNING, COMPLETEING THE FORMATION OF SAID RESISTIVE LAYER DURING A PERIOD NOT EXCEEDING ABOUT 60 SECONDS; AND (B9 CONTINUING THE ANODIZING OF SAID ARTICLE AT INCREASED ANODIZING CURRENT DENSITY TO FORM THE MAIN BODY OF THE FINAL ANODIZED LAYER THEREON, THE THICKNESS OF SAID MAIN BODY BEING AT LEAST ABOUT 50 TIMES THAT OF SAID RESISTIVE LAYER, BY PASSING AN ELECTRIC CURRENT THROUGH AN ACIDIC DISSOLVING ELECTROLYTE, BETWEEN A CATHODE IMMERSEC THEREIN AND SAID ARTICLES AS ANODE, AT AN AVERAGE ANODIZING CURRENT DENSITY MUCH HIGHER THAN 100 AMPERES PER SQ.FT.