Method of anodizing aluminum

Claim 1

THE METHOD FOR PRODUCING A BLACK ANODIC OXIDE COATING ON AN ALLOY CONSISTING BY WEIGHT ESSENTIALLY OF FROM 0.2 TO 0.6% SILICON, UP TO 0.35% IRON, UP TO 0.10% COPPER, UP TO 0.10% MANGANESE, FROM ABOUT 0.45 TO ABOUT 0.9% MAGNESIUM, UP TO ABOUT 0.10% CHROMIUM, UP TO ABOUT 0.10% ZINC, UP TO ABOUT 0.10% TITANIUM AND UP TO 0.15% OTHERS, AND THE BALANCE ALUMINUM WHICH COMPRISES IMMERSING SAID ALLOY IN AN AQUEOUS ELECTROLYTE MAINTAINED AT A TEMPERATURE OF FROM ABOUT 45*F. TO ABOUT 85*F. AND CONSISTING ESSENTIALLY OF FROM ABOUT 25G./1. TO ABOUT 150 G./1. OF SULFORPHTHALIC ACID AND FROM ABOUT 0.1 G./1. TO ABOUT 15 G./1 OF SULFURIC ACID, AS THE ANODE IN A DIRECT CURRENT ELECTIRCAL CIRCUIT WHICH INCLUDES SAID ELECTROLYTE, ANODIZING SAID ALLOY AT APPORXIMATELY CONSTANT CURRENT DENSITY OF FROM ABOUT 25 AMPERES PER SQUARE FOOT TO ABOUT 40 AMPERES PER SQUARE FOOT UNTIL A PRESELECTED VOLTAGE OF FROM ABOUT 55 TO ABOUT 75 VOLTS IS REACHED, AND SUBSEQUENTLY ANODIZING SAID ALLOY WHILE MAINTAINING SAID PRESELECTED VOLTAGE APPROXIMATELY CONSTANT UNTIL A BLACK ANODIC OXIDE COATING IS OBTAINED.

Claim 2

THE METHOD FOR PRODUCING A BLACK ANODIC OXIDE COATING ON AN ALLOY CONSISTING BY WEIGHT ESSENTIALLY OF FROM 0.2 TO 0.6% SILICON, UP TO 0.35% IRON, UP TO 0.10% COPPER, UP TO 0.10% MANGANESE, FROM ABOUT 0.45 TO ABOUT 0.9% MAGNESIUM, UP TO ABOUT 0.10% CHROMIUM, UP TO ABOUT 0.10% ZINC, UP TO ABOUT 0.10% TITANIUM AND UP TO 0.15% OTHERS, AND THE BALANCE ALUMINUM WHICH COMPRISES IMMERSING SAID ALLOY IN AN AQUEOUS ELECTROLYTE MAINTAINED AT A TEMPERATURE OF FROM ABOUT 45*F. TO ABOUT 85*F. AND CONSISTING ESSENTIALLY OF FROM ABOUT 25G./1. TO ABOUT 150 G./1. OF SULFORPHTHALIC ACID AND FROM ABOUT 0.1 G./1. TO ABOUT 15 G./1 OF SULFURIC ACID, AS THE ANODE IN A DIRECT CURRENT ELECTIRCAL CIRCUIT WHICH INCLUDES SAID ELECTROLYTE, ANODIZING SAID ALLOY AT APPORXIMATELY CONSTANT CURRENT DENSITY OF FROM ABOUT 25 AMPERES PER SQUARE FOOT TO ABOUT 40 AMPERES PER SQUARE FOOT UNTIL A PRESELECTED VOLTAGE OF FROM ABOUT 55 TO ABOUT 75 VOLTS IS REACHED, AND SUBSEQUENTLY ANODIZING SAID ALLOY WHILE MAINTAINING SAID PRESELECTED VOLTAGE APPROXIMATELY CONSTANT UNTIL A BLACK ANODIC OXIDE COATING IS OBTAINED.