Compatibility of Aluminum with Alkaline Building Products

Abstract

A series of tests is reported on the reaction of aluminum alloys to alkaline building materials under a variety of conditions. After a discussion of the chemistry of reactions between aluminum and alkaline building products, results of a series of laboratory tests are given. Evaluations of effects by visual inspection, galvanic corrosion current measurement, weight loss and microscopic examination were made. These included subjecting alloy 3003-H14 to a series of exposures to asbestos cement products, insulation materials, alkaline flooring materials, mortar and concrete cured dry and wet, and assessing the effects of galvanic couples to steel in varying ratios up to 1:12, and at spacings from 4 inches to ⅛-inch; effects of chlorides, curing conditions, and others. Mechanism of corrosion in mortar and concrete is examined and a study is made of polarization characteristics of an aluminum-to-steel couple in mortar. Stray currents are cited to explain infrequent cases of severe corrosive attack of aluminum in concrete. Tests reveal, and related service experiences confirm, that aluminum corrodes only superficially when exposed to alkaline building products and that this corrosion is self-limiting in nature. Protective measures may be needed in cases involving dissimilar metals and differential aeration effects in the presence of relatively high chlorides. 6.6.5