Resistance of Aluminum Alloys To Weathering

Abstract

Extensive data selected from tests of many thousands of specimens of aluminum alloys, exposed in various natural atmospheres for periods as long as 20 years, are presented graphically. These data provide comprehensive coverage of the resistance to weathering of outstanding types of wrought and cast aluminum alloys, with particular emphasis on alloys used in architectural and structural applications. Effects of weathering were evaluated by measurement of change in strength and depth of attack of specimens exposed for periods up to 20 years in natural atmospheres and for as long as 52 years in actual service. Aluminum alloys have been evaluated in a sufficient number of different types of atmospheres at widely separated geographic locations to predict with reasonable assurance the performance expected under most conditions normally encountered. The corrosion of aluminum alloys, both wrought and cast, exhibits a “self stopping” characteristic; that is, the rate of attack after an initial exposure period of about one to two years decreases to a very low value, generally to less than 0.2 mil per year. The aluminum alloys displayed high resistance to corrosion and although some differences were noted, these differences often were subordinate to other characteristics of interest, such as strength, formability, appearance and cost.