Use of Boehmite Films For Corrosion Protection of Aluminum

Investigations were made to study the formation of and corrosion resistance of aluminum oxide films formed by reaction between aluminum and water (or wet steam) at 98-155 C. Attention was centered largely on boehmite films. Methods used for investigation of hydrated oxide films on aluminum surfaces (involving dissolution of films or underlying metal) are outlined. A description is given of analytical methods used for determining oxide film thickness and composition. Considerable importance is attached to the influence of metal purity and water purity on boehmite film corrosion resistance. Other topics discussed include influence of pretreatment, commercial applications of boehmite film to protect foodstuff and other containers, and resistance of boehmite films to tap water and lightly aggressive media. It was concluded that 0.01-0.1 N triethanolamine was the filming solution producing the boehmite films with the best overall stability under varied conditions. Maximum stability was achieved with this agent after 4 hours’ boiling time, but even 5 minutes’ boiling time gave films adequate to protect aluminum cans. Boehmite films could be of great practical importance in making aluminum cans suitable for the packaging of beer, milk and other goods for which lacquered cans are unsatisfactory. Considerable data are reported relative to the growing of boehmite films. Extensive reference is made throughout the paper to work done by other investigators on the general subject of hydrated aluminum oxide films. 5.9.4, 6.4.2