1 will destroy the phosphating layer and electrophoretic layer, which is very important to prevent the corrosion of metal substrate.

After the damage, the ordinary repair process can not be repaired. Therefore, many cars painted with sheet metal are prone to rust, which is the reason.

2. After the metal is repaired by sheet metal, the surface will be uneven. At this time, the surface is usually filled with a filler called putty. This kind of putty has different expansion coefficient from metal, and cracks and depressions will appear after a long time, which will affect the appearance of the surface.

The steps of polishing:

1. Clean the whole vehicle. Clean the whole vehicle with a paint cleaner with strong detergency. When using cleaning agent, it is necessary to avoid new scratches caused by particle dust during grinding.

2, water sandpaper grinding. (Be careful not to wear through the paint layer).

3. Rough grinding and fine grinding. Use a machine grinder (electric or pneumatic) and a coarse grinding paste to roughly grind the traces of water sandpaper. Then polishing and fine grinding with grinding paste.

Step 4 polish. The mirror polishing effect of paint film is achieved by using mechanical polishing machine and mirror treatment agent to remove the rotary printing left by rough grinding paste.