Vehicle Body, Paint and Trim
This domain covers body construction and repair, refinishing and interior/exterior trim. Questions test panel preparation, welding and filler use, paint mixing, spray technique, defect recognition and safe handling of body materials.
Body repair and paint
- Body panels are repaired by panel beating, pulling and filling. MIG welding is common for steel; protect glass, wiring and trim from heat and spatter.
- Surface preparation is critical: remove wax, grease, rust and old paint; apply primer to bare metal; sand and clean between stages.
- A typical refinish system is primer, base coat and clear coat. Mix according to the product data sheet; ratios are by volume, not guesswork.
- Spray gun distance, speed, overlap and air pressure control finish quality. Runs come from too much material; orange peel from poor atomisation or incorrect thinner.
- Trim includes clips, weatherstrips, glass, bumpers and upholstery. Use plastic trim tools to avoid broken clips and scratched panels.
Worked example
A base coat is mixed 4:1 with hardener plus 10% thinner based on base volume. For 1 litre of base: reasoning: hardener = 1 ÷ 4 = 0.25 litre (250 mL). Thinner = 10% of 1 litre = 100 mL. Total mixed volume is about 1.35 litres. Add thinner last and stir thoroughly.
Traps
Painting over silicone or wax causes craters; too much filler cracks; using the wrong primer on plastic causes peeling; and dry spraying or heavy wet coats ruin the finish. Always wear respiratory protection and check that the primer is compatible with the topcoat.