The surface is tightened as follows: using a carbon electrode of a semiautomatic welding machine or gas welding, the metal is heated from the periphery to the center of the defective area and the heated metal is pressed down with blows of a wooden mallet and hammer, using a flat support or anvil, the heating and pressing operations are repeated until the required panel surface is obtained.
Unevenness on panels can be leveled using polyester putties, thermoplastics, cold-curing epoxy mastics and solder.
Polyester fillers form reliable connections with panels stripped to the metal. They are two-component materials: unsaturated polyester resin and a hardener, which is a catalyst for rapid hardening of the mixture regardless of the thickness of the filler layer. At 20°C, the drying time is 15-20 minutes. In general, the time of application of the filler is reduced and there is no need to apply it in several layers.
Thermoplastic is produced in powder form. It acquires the elastic properties required for applying it to the metal surface of the panel at 150-160°C. The surface to be filled must be thoroughly cleaned of rust, scale, old paint and other contaminants. For better adhesion, it is recommended to create roughness on the surface using an abrasive tool. To apply thermoplastic, the area to be leveled is heated to 170-180°C and the first thin layer of powder is applied, which is rolled with a metal roller. Then the second layer is applied and so on until the unevenness is filled. Each layer is rolled until a monolithic layer of plastic mass is obtained. After hardening, the layer is cleaned and leveled with a grinding wheel.
Corroded areas of body panels can be repaired with cold-curing epoxy mastics, which have high adhesion, sufficient strength and are easily applied to damaged areas. The mastics contain hardeners, plasticizers (to increase the plasticity of the resin and the impact strength of the hardened composition), fillers (to reduce resin shrinkage and bring the thermal expansion coefficients of the resin and metal closer together).
The text is copied from the online portal VAZbook
Solders such as POSSu-18 or -20 are used to level areas previously filled with solder, build up the edges of parts and eliminate gaps. To prevent corrosion, it is better to use an acid-free method of applying solder.
In case of significant damage, the panels are replaced with new ones using electric welding in a protective gas environment.