How should I prep old aluminum siding before painting? What type of primer is the best for siding?
Remove as much "chalk", dirt and mildew as you can. This is done by power washing or by scrubbing and rinsing. The only times a primer would be needed are:
- if any bare aluminum is exposed; then use a latex corrosion-inhibitive primer;
- if there is still much "chalk" left on the surface, apply a quality exterior alkyd ("oil-based") primer recommended for aluminum siding by the manufacturer. ("Chalk" is powdery pigment on the surfaced of the weathered siding, that comes off when you rub the palm of your hand over the surface.)
After removing the old chalky white from aluminum siding, I was told to wipe the siding with mineral spirits before priming it. Is this a necessary step before washing it? I had to use a sander to remove the road salt and the siding was badly pitted.
No, unless you have some oily contaminant such as road tar on the siding, do not use mineral spirits. The road salt that you removed was probably white aluminum corrosion (aluminum oxide). After you clean and rinse the surface, you will need to prime all areas of exposed aluminum (that is, where you can see the metal), or where any of the white salts were.
For the primer, use a latex corrosion-inhibitive primer. Ask for this at a paint store. You may find it just as easy to prime all of the siding, rather than just the areas mentioned. If you do prime everything, you will get a more uniform appearance from the paint, compared with if you only prime some parts. For the paint itself, use a top of the line 100% acrylic latex house paint in a flat finish.
What type of paint should I use to paint aluminum siding?
In general, use a top of the line exterior 100% acrylic house and trim paint in a flat or satin finish. This assumes proper surface preparation, including removal of dirt, chalk and mildew. Unless metal is exposed, no primer is needed. If bare metal is visible, remove any white oxide with a non-metallic scouring pad such as ScotchBrite, then wash off and rinse, then apply a latex exterior corrosion inhibitive primer to the exposed metal area. As for the paint, use a flat if the siding is at all uneven and/or dented (while the satin finish will provide a rich, fresh appearance, it will accentuate the dents.