My home's exterior is white 30-yr-old aluminum siding. Every year or two, I would wash it with a detergent and bleach mixture and then rinse it using just a garden hose. The house always looked great. Last year, I power washed the siding and the power washing left long blue squiggly lines and streaks on part of the siding. It also took off the white so that the metal is showing in numerous spots. I have been getting different opinions about why this happened and what I can do about it. Can acid rain cause siding to suddenly fail like that? Did we use the wrong types of tools to clean the house? Does aluminum siding eventually get like this - if so, would it happen this suddenly. I'd like to paint the siding but I have gotten so much conflicting advice. Can I paint aluminum siding? What kind of paint should I use? One coat or two? Should I prime before painting? How long will the paint job last? Will the paint be washable? Thank you for any help you can give.