How to Paint over Powder-Coated Aluminium

How to Paint over Powder-Coated Aluminium

1. Clean the Substrate
Any dirt or grease on the metal surface will prevent the subsequent coating from clinging, so all contaminants and debris must be removed. The aluminium can be hand washed using a soft brush or jet washed if the aluminium is extremely dirty. Any alkaline degreasing detergent used for cleaning must be rinsed off with water and left to dry.

2. Remove Corrosion
The powder-coated aluminium may have corroded, and the resulting corrosion deposits must be mechanically stripped off. If powder coating appears chalky, this white rust had better be removed, and a scouring nylon pad should suffice. A power sander can be used to remove any red rust and reveal a smooth metal surface. The next stage is to wipe down the substrate with tack cloths to remove dust from eliminating corrosion.

3. Abrade the Metal Surface
One of the most challenging obstacles in painting over powder coating is ensuring the new layer adheres to the aluminium. Sanding the substrate removes the gloss from the original powder coating to provide a key for the fresh coating to stick. It is worth noting that anodised aluminium will require more abrading than usual. If parts of the powder coating remain, it is important to feather the edges so there aren't any bumps or ridges on the surface. As with removing corrosion, residues resulting from abrading must then be cleaned off.

4. Mask off Adjacent Surfaces
Mask off the adjacent areas that must be protected from primer or paint. Plastic sheeting, decorators tape and masking paper can all be used to stop finished surfaces from being ruined through overspray.

5. Prime the Substrate
Once the metalwork is clean and dry, it can be primed and left to cure. This is best done immediately so the substrate doesn't oxidise or get dirty. There are primers appropriate for different alloys, so a primer for aluminium should be used, and it is best to consult with professional sprayers. To check whether the primer will adhere to the abraded surface, applying a small amount of it to the aluminium is a good idea. If it can be wiped off or smeared, the aluminium should be abraded further.

6. Spray Apply the Top Coat
A range of topcoats is available on the market to suit the wide variety of objects that can be re-coated. A top coat can be selected in a choice of colours and gloss levels appropriate for painting over powder-coated aluminium, but it is crucial to choose the right one. If a primer hasn't been used, the top layer must be selected to adhere to the primer or directly onto the aluminium. Again, a professional spray painting company will ensure that the most appropriate product is used.