CORROSION INHIBITORS FOR ALUMINUM

Abstract

INHIBITORS PROVIDING CATHODIC PROTECTION, ANODIC PROTECTION OF OVERALL GROSS PROTECTION MAY BE CHOSEN BY AN EVALUATION OF THEIR CURRENT-POTENTIAL RELATIONSHIPS AS DERIVED BY POTENTIODYNAMIC MEASUREMENTS. INHIBITORS MUST BE CAREFULLY CHOSEN TO FIT THE PARTICULAR APPLICATION REQUIRED. THE 5000 SERIES ALLOYS, CONTAINING MAGNESIUM AS THE MAJOR ALLOYING ELEMENT, ARE SHOWN TO HAVE GREATER CORROSION RESISTANCE IN SALINE MEDIA THAN DO THE 1100 OR HIGH-PURITY ALLOYS. JEL-TYPE INHIBITORS SUCH AS AGAR-AGAR, BLOCK THE CATHODIC REACTIONS, CAUSING MARKED CATHODIC POLARIZATION. AMINE INHIBITORS ALSO AFFECT THE CATHODIC CHARACTERISTICS. THEY SHOULD PROVE USEFUL IN INHIBITING ALUMINUM CORROSION IN ACID MEDIA. CHROMATES ARE EFFECTIVE ANODIC INHIBITORS. THE INCREASED EFFECTIVENESS OF NICKEL CHROMATE OVER POTASSIUM CHROMATE INDICATED THAT THE EFFECTIVENESS OF CHROMATES WAS NOT ENTIRELY DUE TO THEIR OXIDIZING ABILITY. /AUTHOR/