Process for anodizing aluminum and its alloys

Abstract

Abstract AN ANODIZING SYSTEM USES BOTH POSITIVE AND NEGATIVE CURRENT PULSES. SUCH PULSES ARE ADJUSTABLE TO ACHIEVE DIFFERENT ADJUSTED VALUES OF POSITIVE AND NEGATIVE CURRENTS. THESE VALUES ARE SENSED AND USED TO MAINTAIN AUTOMATICALLY SUCH VALUES. THE RATIO OF NEGATIVE CURRENT TO POSITIVE CURRENT IS PREFERABLY GREATER THAN 3% FOR THE PRODUCTION OF RELATIVELY THICK, DYEABLE, HARD ANODIZED COATINGS AND CONVENTIONAL (NORMAL) ANODIC COATINGS OF LIGHT SHADES OF INTEGRAL COLORS USING A SIMPLE SULFURIC ACID BATH WHICH MAY BE MAINTAINED AT RELATIVELY HIGH TEMPERATURES. CURRENT MAY BE APPLIED AT NEARLY FULL CURRENT DENSITY INITIALLY WITHOUT BURNING. IN SOME CASES, ADDITIONAL MEANS MAY BE PROVIDED TO INCREASE THE THROWING POWER BY ELIMINATING THE NEGATIVE CURRENT AND USING MEANS SUCH AS CAPACITORS OR INDUCTORS TO PROLONG THE DECAY OF THE POSITIVE PULSES, PREFERABLY SUCH THAT THE THEN COMPOSITE POSITIVE PULSES ARE MAINTAINED ABOVE A ZERO VALUE. THESE COMPOSITE POSITIVE PULSES ARE MAINTAINED IN A RATIO AND WAVE SHAPE WHICH YIELDS BOTH GOOD "THROWING" POWER AND HIGH QUALITY, EVEN COATINGS, AND PRODUCES THE ANODIC COATINGS AT RELATIVELY HIGH CURRENT DENSITIES.

Inventors

• 👤 Frederick S Newman
• 👤 John R Thorne
• 👤 John T Hartman

Bibliographic Details