As a rule, dented areas of the plumage are straightened manually using a special tool (metal, plastic, wooden hammers and various mandrels) and devices.
Heat straightening is used for upsetting (tightening) highly stretched panel surfaces. To prevent sudden swelling and deterioration of mechanical properties, the panels are heated to 600–650°C (cherry red color). The diameter of the heated spot should be no more than 20–30 mm.
Tighten the surface as follows:
- using a gas torch, heat the metal from the periphery to the center of the defective area and use a wooden mallet and hammer to push down the heated areas using a flat support or anvil;
- repeat the heating and pressing operations until a smooth 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. Drying time at 200°C is 15–20 minutes. Therefore, there is no need to apply it in several layers and the time it takes to apply the filler is reduced.
Thermoplastic is produced in powder form. It acquires the elastic properties necessary 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 roughen the metal 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 machine.
Corroded areas of body panels can be repaired with cold-curing epoxy mastics, which have high adhesion, sufficient strength and are easy to apply to damaged areas.
Solders POSSu-18, POSSu-20 are used to level areas previously filled with solder, build up edges of parts and eliminate gaps. To prevent metal corrosion, it is better to use an acid-free method of applying solder.