Generally speaking, repainting will increase the thickness of the paint film, and the position of painting will be higher than the original paint surface, so the original paint will be cleaned before spraying new paint. However, it should be noted that the bottom layer of primer is electrophoretic coating, which is the main anti-corrosion layer of automobile. No matter how to clean the original paint, try not to destroy this coating, otherwise the steel plate will slowly corrode. In addition, the touch-up paint will definitely have color difference with the original paint, as long as it is not as strong as the naked eye, it can't be exactly the same.