Painting metal and aluminum siding can become a nightmare if not done right. Over the years I have worked on and repaired many homes with metal siding. Metal siding is real common in mobile homes. Most older mobile homes use aluminum paneling for their exterior siding.
Most painted metal siding seems to last at least 20 years. The reason for this is the paint is baked on in a factory giving it a high quality and nice looking surface. This baked on method is used for painting aluminum and most metals siding that gives the product a long life.
I lived in a mobile home park for a few years and my next door neighbor's mobile home had never been painted and was over 45 years old. He would go out and washed the mobile home once a year with some TSP soap while using a brush on the end of an extension pole to clean the home.
His mobile home might not have looked brand new but it was definitely in great shape. Over the years he had developed a few scratches and some dirt that was hard to wash off but that was about the extent of the damage to the painted metal siding.
Well we painted our mobile home and used an expensive metal primer along with some expensive paint from Dunn Edwards & Co... This paint worked great. We lived there for around four years and never had any problems once the home was painted. Having been in the construction business I knew we had to use a good metal paint primer in order for the paint to stick to the baked on paint process for the metal siding to look good.
Here's my advice to you when painting metal siding.
1. Make sure the metal siding is clean. Use TSP soap along with a scrub brush and scrub that baby clean. The cleaner the metal surface the better the new paint primer will stick or adhere to the old paint.
2. Follow the instructions carefully on the paint primer can when applying the primer. Do not paint below or above the recommended paint temperatures.
3. Make sure you explain to the paint salesman at whatever store you're in that you are going to be painting metal siding. Get the right paint primer.
4. I would love to recommend a paint primer but cannot because I don't want to get a phone call from anyone a few years from now telling me the paint is peeling off of their home. Let that responsibility become the paint manufacturers.
5. Let the paint primer dry for the recommended time as per the directions on the paint primer can. I prefer letting the paint dry at least one week. The reason for this is some paint primer's stay soft for a while and if you paint over them immediately they doesn't seem to bond as good and sometimes will stay soft for a long period of time.
6. Apply your final coats of paint following the manufacturer's instructions on the paint can.
There you have it painting metal siding is all in the preparation of the surface you are painting.
Have fun painting and always read and follow the manufacturer's recommended instructions for the products you are using. These people test their products constantly and know the best way to apply them to any surface.