Chemical strip and Prime or Sand and prime ?

I would be afraid to spend my money trying to paint over top of the existing as it most likely would continue to lose its bond and then the new paint would fail leaving you a much bigger mess to remove. I personally do not like chemical removal if it was mine I would use a D/A and sand the old paint off leaving a good surface for the new primer and paint to adhere to.

If you use any type of stripper you have to make sure that it is totally removed from all cracks and crevices if not you will have paint failure. This is why many of the top classic car restorers have stopped using any type of chemicals. They were having problems over a short period of years with bubbles and chipping/flaking. Many have went to baking or sanding the paint off.

John I don't think any type of blasting is good on an alum trailer but if I was go to it would be with baking soda or walnut shells at a controlled air pressure. I was talking about baking automobiles in a large oven is becoming a very common way of removing paint but that method is not acceptable for a trailer as it would burn up. I would sand the paint off with a D/A then prime and paint from there. A 100 grit disk to start then clean it up with a 220. Next prime and finish. It will amaze you how fast the paint will come off leaving a very paintable surface. A trailer has a vast amount of places that are nearly impossible to remove chemicals from unless you removed all the siding, stripped it, neutralized it then reinstalled it ready for paint. I know people have done it but also many have had problems down the road that they never knew what caused them. Many manufactures won't stand behind there paint if installed over a stripped surface.

John I paid to have my Plymouth taken apart and painted this winter and I talked to four different quality shops that does restoration painting and they all said the same thing. They told me that if their is a problem near a seam the paint companies will balk at standing behind the products so I now have a complete set of pictures of it being sanded bare and repainted.

Thanks for the great feedback... Seems there's always pros & cons on all decisions.. some decisions bigger then others.
I think I'll try both in spots and see what the level of effort I'll need to commit too.
Cheers !

I think if the paint is peeling off, it's best to remove all the old paint and start over. If the old paint is chalky but not peeling, you can get a good base by sanding with 220 and paint. The old base is just as good a primer as stripping and priming. I painted my Airstream Argosy, sanding and painting, and just primed the bare aluminum. I painted it with Rustoleum boat paint, and it came out great. Just my $0.02.
Roger