Aluminum Interaction with Cementitious Materials in a Coastal Environment

Florida coastlines are highly corrosive environments conducive to the deleterious interaction between dissimilar building materials, which will result in significant damage and costly repairs. Often, cementitious materials, such as stucco (or plaster) and exterior tile-setting materials (thinset, mud bed, and grout) are in direct contact with the aluminum frames of sliding glass doors, windows, storefronts, balcony railing, and plates for sunshades and trellises. Due to the close proximity of the ocean and resulting saltwater spray, the corrosion process is accelerated. The proper use of special coatings, and/or separation of these dissimilar materials, becomes the difference between costly failures and an enduring building enclosure. Often, the coating applied to the aluminum frame meets the performance testing requirements of AAMA. However, handling and installation results in scratches to the coating, and thus, opening pathways for corrosion to occur. This paper discusses the phenomenon, current code requirements, industry standards, AAMA performance testing, and presents case studies.