I’ll read others’ responses with interest.
I want/need to acid wash my trailer and I have been a paranoid research queen about this for a long time.
As I understand it, the key is to go to the place that really rinses it off thoroughly. If you don’t and the acid remains on the trailer, the low pH of the acid starts to pit the aluminum, and that’s how you get the chalky, grey metal that looks so bad.
Also, I think that it’s a fairly polluting process (again because of the amount of acid and rinsing water involved), so you might have a bit of a hard time finding a place that really does it right (or wrong, as your politics might be).
Usually, you need a very local-to-you and expert answer from another horseman or truck wash. Should your travels include long-distance truckers, I’d certainly ask one of those guys where they go. Or, I’d ask a pretty big trailer place where they send their clients, or I’d wait until I was somewhere fancy (think of places like Wellington) and ask the person next to the shiniest-looking rig where/how he maintains his.
Oooh… and a couple of other good ideas: The truck and also AirStream people have on-line forums that are every bit as good as COTH at what they do. If you post this question on one of those, I bet you’ll get the best advice ever.