Vehicle Body, Paint, Trim and Welding Basics
Body, paint and trim
The exam covers body panels, panel beating, fillers, primers, topcoats, clear coats, trim fasteners, glass and basic welding. Prepare metal by cleaning, straightening and applying primer; body filler is for minor imperfections, not structural repair. Follow the paint system: primer, base coat, clear coat, with correct flash-off times. A respirator and ventilation are mandatory with isocyanate paints. Trim clips and adhesives must be replaced, not forced. Check panel gaps and corrosion protection after repair.
Welding basics
MIG welding uses a continuous wire electrode and shielding gas; TIG uses a tungsten electrode and separate filler; arc welding uses a flux-coated rod. Spot welding is common in body assembly. Clean the earth point, set current for thickness, and protect glass, ECU and fuel lines from heat. Galvanized metal needs fume extraction. Never weld a fuel tank unless it has been purged and certified safe.
Worked example
A repainted panel shows small crater-like holes, called fish-eye. Reason: oil, silicone or wax contaminated the surface or air line. The cure is to remove the contamination, clean the gun and air supply, and recoat according to the paint maker’s system. Adding more clear coat will not fix fish-eye.
Traps
Common marks are lost for welding on a vehicle with the battery connected, sanding through primer, using filler over rust, and skipping the sealer. Orange peel is usually gun setup or viscosity, not a reason to sand and polish immediately.