Powder coatings are still considered a novelty by many contractors, and given the long experience and track record of liquid coatings it is considered safe to continue purchasing and installing liquid-coated parts.
The truth is that metal for construction has been powder coated for over 40 years, and technically the properties are every bit as good as liquid analogs. Whether for aluminum façade profiles and panels, metal ceilings, lighting units, fencing and railings, or internal partitioning, there is a powder coating alternative, and a qualified job shop capable of coating the parts.
Powder coatings are essentially the same as liquids, containing polymers as the backbone, with pigments to give the color and special additives to give specific properties, such as lower gloss, textures, soft-feel or anti-yellowing. The difference is that in liquid paints these are dispersed in water or solvent, where for a powder coating they are in dry form, and become liquid through the application of heat.
Metal parts are coated by charging the powder electro statically and spraying it at the metal to form a thin layer. The metal parts then move through an oven at typically 375 F where the polymer melts to form a liquid, flows to make a smooth film, and reacts to form a 3-D network.
The end result is a tough, durable film. As there is no solvent, there is minimal waste, no emissions to the atmosphere or need for incinerators, and no wasted fuel in transporting solvent which does not end up in the finished coating. The Powder Coating Institute promotes these properties with its Powder Coated Tough stamp, which has the tag line “Stronger. Greener. Better.”
Around 20 percent of the cost of a modern high-rise building is the façade, with the metal contributing a major part of the cost. Repairs and re-coats are a costly burden so it is important to choose the right materials and partners to work with. The American Architectural Manufacturers Association (AAMA) is an industry body bringing together suppliers of glass, aluminum, wood, vinyl and other window materials, coatings, pre-treatments, adhesives and sealants. Collectively they have written and continued to refine a series of standards for the coating materials used on aluminum for fenestration.
Readers may well have heard of AAMA 2603, 2604 and 2605.
These are the standards which set out the tests to be met by coatings for aluminum, covering important items such as mortar-, acid-, and detergent-resistance, corrosion resistance and weathering. No matter whether liquid or powder, the coatings for the aluminum need to meet the same standard.³