SLR_dave, I have been using this product for approximately twenty years and you are correct, they do not recommend it for use over automotive paint as it can stain or bleach the surface colour. I only use it in area where there is no other alternative and as you can see, it was a huge improvement over what was there. Even natural products like molasses can damage paint finishes if not used correctly. Secondly, as you stated Ranex will not prevent rust coming back, it is just a rust remover, with good paint I always apply polish after to reduce the rust returning, but on paint that has "had it" like this ute, I would normally apply a satin clear coat over the top to protect and retain the "Patina" look that some people like to have. I work with a lot of guys who love the rat- patina style of car.

As this ute will never see rain or a wash again in its present state, I will leave the surface as is.

Thanks for you comments and sharing your research.