If the paint is damaged, you can see the color of the underlying primer (for example, the bottom of the paint). In general, bumper, rear view mirror and wheel eyebrows and other parts are plastic parts, will not rust, the problem is relatively simple. If it is scratched to the body of the steel plate, it will fill the paint, otherwise, even if it is a very small damage, the steel will begin to rust, even if the use of the best car repair paint, the effect is not ideal.