What Type of Paint Can Be Sprayed on Galvanized Steel?
Water-based paints are a must
By Stevie Donald
Unlike most kinds of metal, galvanized steel should never be sprayed, primed or painted directly with oil-based or alkyd paint. Oil-based coatings react with the zinc coating, creating a film that will cause it to quickly start peeling. Instead, paint galvanized steel with water-based coatings. For steel roofs, sheds, gutters and downspouts, use water-based primer and paint. Your other options for spraying galvanized steel are epoxy and powder coatings.
Galvanized steel is dipped and coated with zinc, which makes it extremely rust-resistant and capable of lasting 50 years or longer, according to the Galvanizers Association. Galvanizing creates a coating that degrades slowly and evenly and does not require protection from paint. It's often painted for aesthetic reasons to improve or alter the appearance. In very harsh environments, paint can add extra protection .
Galvanized steel can be painted at any time, either right after installation or after it has become very weathered. The Galvanizers Association suggests that waiting to paint until the surface has already provided many years of service is the most economical approach. When the steel is new, it needs to be washed with ammonia and water or a cleaner designed for galvanized steel. As it weathers, it develops a white powdery film, which must be scrubbed off prior to painting.
Clean, rust-free galvanized steel does not have to be primed, although both Sherwin-Williams and the Galvanizers Association recommend priming for maximum durability. The correct primer depends on the size and scope of the project and the type of top coat. Large interior commercial jobs, especially where maintaining good air quality is important, can be sprayed with a two-part water-based epoxy system. For most other applications, an acrylic primer designed for metal surfaces is sufficient. The Rohm and Haas Paint Quality Institute recommends two coats of primer on exterior surfaces if they will be exposed to extreme weather.
Water-based epoxy, 100 percent acrylic paint, and water-based polyurethane or urethane coatings can all be sprayed on galvanized steel. Although not typically recommended, alkyd or oil-based paints may be applied if the steel has been completely primed, according to the Paint Quality Institute. Direct-to-metal (DTM) paints are a relative newcomer to the painting industry and are water-based coatings that can be sprayed directly onto galvanized steel and other metals without a primer.
For smaller projects, powder coatings are sprayed on galvanized metal and cured at high heat. Powder coatings produce a mirror-like, hard plastic finish but require specialized equipment for application and curing.
About the Author
Stevie Donald is a regular contributor to DexKnows. She has been a painting contractor since 1979.
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