Automotive Body Repair & Painting NC II common mistakes
Automotive Body Repair & Painting NC II · Understand the traps and how to avoid them.
Spraying the first coat too wet and too close, then continuing to add coats over a still-wet film instead of letting it flash off, producing runs and sags.
Candidates chase coverage on the first pass and misjudge flash-off time, especially in warm shops where the surface looks dry before solvent has actually left the film.
What to do instead
Apply thin-to-medium wet coats at the specified gun distance and overlap, and wait for the recommended flash-off (film turns uniformly matte, no longer glossy-wet) before the next coat; keep a coat count written on the job card.
Mixing primer, sealer, or topcoat by eyeballing ratios instead of measuring with a mixing stick or scale, and skipping the induction time on products that require it.
Candidates rely on habit or judge by colour/viscosity, and they skip reading the product data sheet because they assume all products mix the same way.
What to do instead
Measure each component with a graduated mixing stick or scale at the ratio on the technical data sheet, record the batch, and observe the stated induction and pot life before spraying.
Sanding through the primer or clear coat on edges, body lines, and raised features because the same pressure and grit are used as on flat panels.
Candidates keep a flat pad and uniform pressure across the whole panel and do not reduce grit or pressure on high spots where film builds thin.
What to do instead
Use a finer grit and lighter pressure on edges and character lines, sand by hand with a flexible block near edges, and check film thickness or use a guide coat to stop before breaking through.
Masking only the obvious areas and leaving gaps at door shut lines, panel gaps, badges, and trim holes, so overspray lands on glass, rubber, or interior surfaces.
Candidates work quickly and assume the spray pattern will not reach recessed or reverse-angle areas, and they skip backing paper behind openings.
What to do instead
Mask in a fixed order (glass, rubber, trim, openings, then edges), back-fill gaps and holes with paper or foam tape, and do a walk-around check with the gun before spraying.
Judging panel damage and alignment by eye only, without measuring with a tape, straight edge, or gauge, then filling over stretched or creased metal.
Candidates trust visual appearance and want to move to filler quickly, and they are unsure how to use measuring tools to confirm panel gaps or structural dimensions.
What to do instead
Measure panel gaps and reference dimensions before and after repair, identify stretched or creased areas, and plan metal straightening or panel replacement before any filler is applied.
Over-applying body filler in thick layers in one pass and sanding it before it has fully cured.
Candidates try to fill a deep dent in a single application to save time and start sanding when the surface feels firm but is still soft underneath.
What to do instead
Apply filler in thin, staged layers within the product's maximum thickness, allow full cure per the data sheet, and shape with a long block rather than digging with fingers or a small pad.
Using a grinder or power tool on a panel without securing the workpiece or checking the disc rating and guard, and using the tool one-handed near edges.
Candidates rush setup, are unfamiliar with the tool's rated speed and guard orientation, and underestimate kickback on thin sheet metal.
What to do instead
Clamp or support the panel, fit the correct rated disc with the guard in place, grip the tool with both hands, and keep the disc angle and direction of rotation away from edges and the body.
Storing or handling solvent-soaked rags, mixed paint waste, and used filters as ordinary trash, or pouring thinners down the drain.
Candidates are focused on finishing the job and are not clear on which wastes are hazardous or where the designated containers are.
What to do instead
Segregate waste at the point of generation into labelled solvent, paint-sludge, and general-waste containers, keep solvent rags in a closed metal can, and follow the shop's disposal procedure before leaving the bay.
Reassembling trim, lights, and panels without checking fastener torque, clip seating, and panel gaps, and without a final function check before sign-off.
Candidates treat reassembly as the last quick step and skip the inspection checklist, assuming the fit will be acceptable because the parts came off the same vehicle.
What to do instead
Follow the reassembly sequence, confirm clips and fasteners are fully seated and torqued to spec, verify gaps and flushness, and run a documented function and visual inspection before releasing the vehicle.
Skipping or shortening the pre-clean and degrease step, and touching cleaned panels with bare hands before painting.
Candidates assume the panel is clean after sanding or blasting and do not recognise that skin oils and sanding residue cause fisheyes and poor adhesion.
What to do instead
Degrease with the specified cleaner, wipe dry with clean lint-free cloths, use a tack cloth immediately before coating, and handle cleaned panels with gloves or by edges only.