Imagine all of the staircases, handrails, pipes, metal door frames, ceiling joists and lampposts in and around your commercial building – These are just a few of the metal surfaces on your property that need protection from the harmful effects of wear, tear, and weather.
In order to maintain the integrity of your commercial building, you need to know what types of metals are on your property and how each type of metal should be protected and coated.
There are two categories of metal. They are:
Ferrous – Containing Iron
Non-Ferrous – Not Containing Iron
The simplest way to determine whether a metal is ferrous or non-ferrous is with a quick magnet test. Grab any magnet – if it sticks to the metal, it’s a ferrous material. If not, it’s non-ferrous. This is the first indicator of your type of paint and primer.
It’s important to identify which type of metal you’re dealing with on a commercial project, especially in Florida, because ferrous metals are the ones that are known to rust. And while ferrous metal, like steel, often arrives at a jobsite pre-primed with a factory primer, this coating will not prevent rusting. This is because metal corrodes when it is exposed to our hot, humid Florida environment, whether interior or exterior.
Some metals, like stainless steel, form an oxide layer that is stable and protective, while other metals like zinc corrode, producing a weak, non-protective layer. The solution is often coating the metal surface with a primer and paint to provide barrier protection.
What about galvanized metal?
Galvanized metal is simply ferrous metal coated with a layer of zinc. The value of galvanizing comes from the corrosion resistance of zinc, which, under most conditions, is considerably greater than that of iron and steel. However, all owners and property managers should consider that painting galvanized metal demands regular maintenance.
If galvanized metal is present, surface preparation is a key factor in achieving good paint adhesion. After the metal is cleaned, it then becomes a good candidate for DTM coatings.
What does “DTM” mean?
DTM, or “direct-to-metal,” coatings are paints composed of 50 percent primer and 50 percent top coat. DTM paints allow painters to bypass primer and begin immediately applying the top coat. A DTM coating is latex-based, so it does not prevent against rusting. If you need an exterior surface painted, it’s recommended you use oil-based paint, commonly referred to as industrial alkyd enamel.
Protecting Bare Metal
Finally, bare metal is untreated ferrous metal that must be protected with a rust deterrent. If rust is already present, it will need to be carefully removed prior to re-coating. This is completed by scraping the surface with a brush, sanding, abrasive blasting, or dissolving the rust away with acidic solutions, depending on the project. In addition, all new ferrous metal surfaces should be primed with a rust inhibitor prior to finish coat application.
While primers are designed to offer an initial protective coat and provide a base for the finish coat, it is the finish coat that delivers the extra layer of protection against moisture and adds the aesthetic appeal.