1. First use a sanding machine or a coarse sand cloth to polish or roughen the metal parts, remove the rust, and if necessary, use a chemical solvent to remove dirt such as surface grease. If it is iron, it is better to use galvanized parts;
2, after the metal surface treatment is dry, clean and then use oily putty scraping, as thin as possible to prevent the putty from drying or aging process, shrinking or cracking or falling off
3. After the putty is completely dry, smooth it and carry out the subsequent surface painting operation.