Coated Metal Building Restoration
While anodized aluminum was the dominant material utilized in curtain wall in the 1960’s and 1970’s the use of factory applied organic coatings became prevalent in the 1980’s. Painted or organic coated finishes became popular with architects due to an unlimited choice of colors, consistency of color, resistance to corrosion, its availability in small batches and its cost-effectiveness. These coatings were eventually available in metallic finishes to achieve the look of an anodized aluminum-type appearance but in the form of a coating. The evolution of the use of the Kynar resin in long-lasting coatings for finishing architectural metals further advanced the appeal of these finishes. Kynar based finishes are now the standard for high performance architectural coatings.
Initially, silicone waterproofing sealants or caulking were utilized in panel joints to prevent infiltration of moisture into these wall systems. The erosion of silicone and plasticizers from the sealants creates rundown staining on panels and extrusions that can be difficult to remove. The combination of a silicone residue with the accumulation of pollution and airborne soil can result in an unsightly appearance on the finish that can be difficult to remove. More recently, rain screen or dry joint wall systems have become the standard in eliminating the sealant problem. Regardless of the curtain wall design, maintenance of the painted finishes has always been necessary to maintain their intended appearance. While the very hard finish of anodized aluminum can be cleaned and renewed using abrasive cleaning methods, the painted finishes cannot. Their softer finish can be easily abraded, scuffed and scratched if abrasives are utilized. For this reason, the process for cleaning painted finishes requires a clear cut understanding of what can and can’t be used for renewing the appearance of these finishes. It is especially critical to design and implement a technically sound maintenance program that meets the aesthetic needs of the building while maintaining its functionality long into the future.