[special-K]

That was it...Ospho. Small parts you let soak. A fender you would want to keep brushing it on. I have another product in a pump spray bottle that does the same thing, but can't read what the label says or recall where I got it. you could pump spray Ospho, but don't expect the sprayer to last real long. It's phosphorous acid, I believe, that does the trick

Tractor supply and advance Auto sell convertors that leave a white oxide crust you have to remove. I stay way from that crap. By the time you get that crust off you lose the coating. Permatex has one in spray bomb that works really well. It turns rust black and leaves clear coating that lasts a good 6 months. That's what I spray on my old metal signage on my shop to keep it in a stable stat. That is what I would spray on a surface rusted truck. You can prime straight over these types of convertors