Vehicle Body Painting and Refinishing
Vehicle Body Painting and Refinishing
This domain tests surface preparation, primer and topcoat systems, colour matching, blending, spray technique and defect correction. The exam favours process control over speed.
Core rules
- Clean with the correct pre-cleaner, then sand and repair. Remove sanding dust and contamination before primer.
- Use the specified primer and sealer; epoxy primer provides corrosion protection, while flexible primers suit plastics.
- Metallic and pearlescent colours require uniform agitation and a consistent spray pattern. Colour match by spray-out card, not by eye under poor light.
- Blend basecoat into adjacent panels and clear the whole panel or blend area. Observe flash times and pot life.
- Spray distance, overlap, air pressure and booth temperature control texture and runs.
- Identify defects: orange peel from poor atomisation; runs from heavy coats; fish eyes from contamination; solvent pop from too little flash time.
Worked example
A metallic quarter panel needs a blend into the rear door. Reasoning: prepare and seal the panel, apply basecoat to the repair, then blend base into the door using a reduced blend coat. Clear the full blend area and allow proper flash time. Stir the metallic constantly and use a spray-out card to confirm colour under booth lighting.
Traps
Over-thinning; spraying clear too wet; skipping flash time; not cleaning before tack-off; matching colour in daylight and spraying under different light.
Key points
Clean, sand and seal before topcoat. Metallic base needs constant agitation and a spray-out match. Blend basecoat and clear the entire blend area. Respect flash times and pot life. Orange peel, runs, fish eyes and solvent pop each have a specific cause.