Car steel is not perfectly refined to start with. What makes the difference is sealig the steel from long term weathering effects. Use a scotch brite to get what u can see, but dont look at it microscopically or u wont sleep at night. I have a 39 chevy thats been sitting in the woods with oak tree sap on it for 30 years with no paint and theres only a few places rusted thru. It takes longer than we think it does to eat metal.