squeezed lemons makes wonders on deep rust.i just rinsed with hot water and so far the paint on my trunk lock shield holds the paint(4 months)it was an experiment,but its pretty impressive how good it works.i was making limoncello with home made booze and got some lemons over,so i tried it.the result is totally clean metall,maybe you should rinse in something else to make it last?im happy so far