I got good results with the Clean Strip concrete and metal prep. I got a cheap one gallon pump sprayer and sprayed some plows and other implements they stay outside. Nothing seems to happen until it rains, then it all turns streaky white like spilled milk. At that point, the rust is stopped according to my Google research. My pressure washer blew the white crust off and left the metal dull grey. Those do not get painted, they should have been treated with Fluid Film after they were used. I also sprayed another protect that was painted back in the sixties. It has been in the woods for at least thirty years and has light surface rust and very little paint left. After I sprayed it, I pushed it into the garage for some major "repurposing". It was much easier to grind and weld on it after treatment. The rust is white chalky. Have not pressure washed that one, yet. My son and I have been making a three wheeled go kart from spare parts and scrap found behind the barn. Some painted, some rusty, some stainless. We are done tacking stuff onto it, so we removed the seat engine, handlebars cables , chains and jack shaft so I can put it on the bench and have a welding party on it before painting. I sprayed it, waited overnight and pressure washed it. I am amazed at how it looks. Will post pics of it thus afternoon. No rust, but most of the paint is still there.