Body Filler, Corrosion Protection, and Seam Sealing
What this domain tests
This domain tests body filler use, corrosion protection, and seam sealing after non-structural repair. The exam checks substrate prep, filler thickness, primer systems, cavity wax, and drain paths.
Core rules
- Apply filler only to clean, bare, properly prepared metal; remove rust, paint, and contamination; use epoxy primer as specified.
- Follow OEM filler thickness limits; thin, cured coats are better than a thick fill. Do not use filler to bridge rust or structural gaps.
- Corrosion protection is a system: zinc-rich primer on bare steel, epoxy primer, seam sealer at factory seams, and cavity wax in enclosed areas.
- Use paintable seam sealer where the OEM does, and do not block drains, slots, or access holes.
- Seal after primer according to product directions; topcoat only compatible products.
Worked example
A repaired door skin has bare metal at the hem. The technician applies epoxy primer, a thin filler coat, sanding, sealer, and cavity wax inside the door. Reasoning: the hem traps moisture; primer and wax restore the barrier, while excessive filler or sealer over bare metal can fail and hide corrosion.
Traps
Filler over paint or rust; thick filler instead of metal straightening; sealer over bare metal; blocking drains; skipping cavity wax; using non-paintable sealer on visible seams.