PAINTING BARE METAL
The preparation for painting most metals is in 3 parts – Clean, Prime and Paint. Sometimes we can skip a step, depending on what shape the metal surface is already in, but generally you need to first clean, then prime, then paint the metal surface.
On unpainted metal the first step is to degrease the surface using a water based degreaser to get rid of any grease that may cause the paint not to adhere to the metal.
Remove any mill scale or rust that may be on the metal. If you’re working on mild steel, sand these areas to a bright metallic surface. If you’re working with galvanised metal, don’t sand as you will remove the zinc protection from the metal.
In this case and cases where you can’t get to all the rust, apply a rust converter which will convert the rust to a stable substrate.
Prime the surface using a roller for the larger areas and a brush to get into the corners. Metal primers are available in water based form these days and can be used on mild and galvanised steel. Clean up is easily done by washing your brushes and rollers in water and the product is much more eco friendly than an oil based paint.
The next step is to apply a universal undercoat. Now these days there are topcoats on the market that contain the undercoat, so you can skip this step if you use one of these. This will save a lot of time and effort. Chat to your paint expert to get the right products for the project.
Now we’re ready to apply an enamel topcoat. These are available in oil and water based products.
Water based enamels are new on the market and give the same protection as their oil based counterparts. Some enamels even contain the undercoat, as I’ve just mentioned, so choose your topcoat with care. Often it’s a good idea to find out what topcoat your going to finish with and then work backward and determine how you’re going to prepare to the surface.
For exterior metal a gloss or semi-gloss is usually used. Glossy surfaces will reflect the heat of the sun, whereas matt finishes absorb heat. However, a gloss finish will highlight every imperfection in the surface, so your surface will need to be smooth and without too many defects if you choose to use a gloss finish.
Application of the topcoats can be done with a roller which will get the job done a lot faster than when using a brush. The 16cm roller with a foam re-fill will get the job done fast. It’s always a good idea to apply two thin topcoats, as opposed to one thick coating. A thick coating of paint will form a skin on the surface. This will seal the surface, preventing the paint beneath from curing. It will remain soft and will take a long time to cure, during which time the surface may rust.
The finished product will be well protected against the elements for many years if the metal is well cleaned, well primed and painted with two topcoats of quality enamel, with an undercoat if necessary.