Non-chromated surface preparation materials and methods for corrosion

Abstract

Surface preparation methods and materials that provide corrosion protection for aluminum and its alloys without the use of chromate and that protects aluminum surfaces against corrosion nearly as well as a chromate conversion coating. In accordance with the present methods, aluminum parts are degreased in a general purpose cleaner and rinsed in hot tap water. The parts are then cleaned using alkaline cleaner and then rinsed in cold tap water. The parts are then deoxidized using one of two alternative steps. The parts may be deoxidized using a 20-25 volume percent Smut-Go NC solution at room temperature for 15-25 minutes. The parts may alternatively be deoxidized using a solution of 10% HNO.sub.3 and 3% NaBrO.sub.4 dissolved in water at room temperature for 15-25 minutes. The deoxidized aluminum parts are then rinsed in cold tap water. The parts are then immersed in boiling deionized water and then sealed using a 1% LiNO.sub.3, 10% Al(NO.sub.3).sub.3 and 10% aluminum silicate solution. The sealed parts are sealed a second time using a solution of 13-15% Kasil #1 with a dissolved corrosion inhibitor. The sealed parts are finally dried in air for about 24 hours or in an oven for 3-4 hours at 150 degrees Fahrenheit. Aluminum parts treated by the present methods meet the requirements of MIL-C-5541 without using hazardous chemicals.