When car scratch repair, why need to paint the whole car paint?

If you simply spray paint locally at the scratched position, there will be a more obvious boundary between the new and old paint layers due to the passage of time. Old car paint will turn yellow under long-term exposure to wind, sun and rain, and the yellowing speed will slow down as time goes by. The new paint uses complex fine-tuning techniques to closely match the color of the old car paint. Based on this color, the new paint will also start to yellow, and the yellowing speed is faster than that of the old car paint. The two paint surfaces are assembled on the same plate, and the difference in yellowing speed can easily lead to the generation of the boundary between the old and new paint surfaces, which is not conducive to the beauty of the car paint.

The entire painting process includes multiple links such as sheet metal repair, dust filling, grinding, primer, color paint, varnish, baking, polishing, etc. Sandpaper grinding is obviously impossible to polish only the place that needs to be painted very accurately, choose the entire surface to polish , to ensure that the entire surface of the spray paint is smooth and flat.

Because the paint surface of the car body is often exposed to the wind and the sun, the color of the car paint will age and discolor. It is difficult to adjust the color of the car paint to match the color of the car paint after the later touch-up paint needs to be adjusted. The interface between old and new paint is very difficult to handle, and it is easy to have color difference if you don't make a whole piece.