CTVET Ghana Certificate II - Auto Body Repair & Spraying cheat sheet

Hierarchy of control, most to least effective: elimination, substitution, engineering controls, administrative controls, PPE. PPE is the last line of defence.

Isocyanate hardeners in two-pack paints are sensitisers; asthma can develop after a single overexposure. Any 2K product requires an air-fed respirator, not a dust mask.

Respiratory protection selection: dust masks (FFP2/FFP3) for sanding dust only; A2P3 cartridge or air-fed hood for solvent vapour and isocyanate spray.

Spray booths need a face velocity typically around 0.4–0.5 m/s with the filter loading monitored; below-threshold airflow means stop spraying.

Flash-point rule: solvents with flash point at or below 23 °C (e.g. acetone, thinners) are highly flammable; keep ignition sources and hot-work permits away from mixing areas.

COSHH-style assessment order: identify hazardous substance, assess exposure route and level, control it, record, review when process or product changes.

Waste segregation: waste thinner, gun-wash sludge and paint tins are hazardous waste; empty dried tins may be scrap. Never pour thinners down drains.

Manual handling guide: keep the load close to the waist, avoid twisting while lifting a panel, and use two people or a panel trolley above roughly 25 kg.

Fire response: water is unsuitable on solvent fires; use foam, dry powder or CO2, and know the location of the nearest extinguisher before starting hot work.

Air tool rule: impact wrenches need high flow at moderate pressure; a spray gun needs stable pressure at the cap. Regulate at the gun, not only at the compressor.

Compressor maintenance schedule: drain receiver condensate daily, clean or replace intake filter, check safety valve and belt tension, change oil per maker's interval.

Air-line layout: fit a coalescing filter and water trap before the spray gun; moisture causes fisheyes and dull patches in fresh paint.

Sandpaper grit logic: lower grit number = coarser cut. Typical sequence for bare metal repair is 80 → 120 → 180 → 240, then primer and 400–600 wet for topcoat.

DA sander: dual-action orbit reduces swirl marks; use a soft interface pad on curves and keep the pad flat to avoid gouging.

Torque wrench care: return to lowest setting after use, never use it to loosen fasteners, and recalibrate on a schedule.

Measuring tools: a steel rule and dividers check panel gaps; a tram gauge or dedicated body gauge checks diagonal symmetry of the body shell.

MIG welder setup for thin body steel (0.8 mm): low amperage, 0.6–0.8 mm wire, short stitch welds to limit heat distortion.

Lockout: before working on a compressor, booth fan or lift, isolate the energy source, tag it and confirm zero energy before starting.

Substrate identification: bare steel, galvanised steel, aluminium and plastics each need different preparation; a magnet separates steel from aluminium, a test panel confirms plastic type.

Surface preparation sequence: remove trim and wax, wash, degrease, sand, clean with a tack cloth, then apply the correct primer.

Primer types: etch primer for bare metal and aluminium, epoxy primer as a sealing/anti-corrosion base, polyester filler for shaping, high-build primer for levelling.

Filler rule: apply polyester body filler in thin layers, never thicker than the maker's stated maximum; thick filler cracks and shrinks.

Sanding direction matters: feather the repair edge progressively; a hard edge left under primer shows as a ring in the topcoat.

Mixing ratio discipline: 2K products are mixed by volume with the stated hardener ratio (commonly 2:1 or 4:1); wrong ratio causes soft or brittle films.

Pot life: the working time after adding hardener. Mix only what can be sprayed within pot life; gelled paint must be discarded, not thinned.

Galvanised and aluminium surfaces must not be abraded with tools contaminated by bare steel, to avoid embedding iron particles and causing corrosion.

Tack cloth removes dust without leaving residue; a solvent wipe alone does not remove sanding dust.

Removal order: disconnect battery where electrical parts are involved, label and bag fasteners, note shim and alignment positions, then release spot welds or bolts.

Spot weld removal: drill through the weld with a dedicated spot-weld drill, not the panel; centre-punch first to prevent the drill wandering.

Panel gap check: measure and record door, bonnet and boot gaps before removal so the panel can be refitted to the original tolerance.

Bolt-on panels (wings, doors, bonnets) are aligned by hinge adjustment; welded panels (sills, quarter panels) need cutting, alignment and welding.

Heat shrinking: a shrinking disc or controlled heat plus a dolly removes stretched high spots; too much heat destroys the steel's structure.

Dent repair order: rough the shape first with hammer and dolly, then finish with a shrinking or planishing hammer, then filler for minor imperfection only.

Corrosion protection after welding: clean welds, apply weld-through or zinc-rich primer to bare steel, then cavity wax inside closed sections.

Structural parts (chassis legs, pillars, sills on unitary bodies) need the maker's specified section and weld type; substituting thinner steel weakens crash performance.

Replacement panel check before fitting: confirm part number, side, material and whether it is supplied with e-coat; e-coat must be sanded and primed before topcoat.

Gun setup: fluid knob controls paint flow, fan knob controls pattern width, air screw controls atomisation; set the fan to roughly 20–25 cm at spraying distance.

Spraying distance is typically 15–25 cm, gun perpendicular to the surface, 50% overlap per pass, constant speed, trigger released at the end of each pass.

Common defects and causes: orange peel from too little thinner or too much air pressure; runs from too wet a coat or too slow a pass; dry spray from too far away or too fast.

Fisheyes come from silicone or oil contamination; blushing (milky finish) comes from moisture in the air line or high humidity.

Flash-off time is the wait between coats for solvent to escape; skipping it traps solvent and causes solvent pop or blistering.

Two-pack topcoat: mix base and hardener, add thinner per the maker's data sheet, strain through a filter, and apply wet-on-wet coats within the recoat window.

Clearcoat is applied over basecoat for gloss and UV protection; basecoat alone is not durable.

Curing: force-cure in a booth at the maker's temperature/time; do not polish fresh paint before it is fully hard.

Colour matching: check the variant under the correct light (daylight or booth D65-type lamp), spray a test card, and compare before committing to the whole panel.

Alignment checks: measure diagonals, panel gaps and reference points against the maker's body dimensions before and after structural repair.

Unitary body logic: damage in one area can distort distant mountings; always check suspension and engine mount points after a heavy impact.

Panel gap and flushness are set by adjusting hinges, catches and shims; set the gap first, then the flush, then confirm the latch closes without force.

Door alignment order: rear edge to quarter panel first, then front edge to wing, then check the waistline and roof line.

Suspension and steering geometry (camber, caster, toe) is checked on an alignment rig after structural or suspension work, using maker's settings.

Trim and glass fitting: use new clips and seals where specified; a reused brittle clip causes rattles and water leaks.

Fastener discipline: use the specified grade and torque; torque-to-yield bolts are single-use and must be replaced, not reused.

Final assembly check list: all fasteners present and torqued, electrical connectors seated, no tools left inside panels, water test before handover.

Job card essentials: vehicle details, registration, mileage, reported fault, agreed work, parts used, labour time, technician signature and customer sign-off.

Estimate structure: parts cost + labour hours × labour rate + consumables + paint materials + VAT or levy = total quoted price.

Variation rule: any extra damage or additional work found after stripping must be authorised by the customer in writing before proceeding.

Record keeping: keep before/after photographs, paint mixing records and warranty terms; these resolve disputes and support warranty claims.

Customer communication: explain the repair in plain language, state realistic completion dates, and notify promptly if the date changes.

Pricing for a small shop: know the fixed costs (rent, power, wages), the variable cost per job, and the margin needed to stay viable.

Entrepreneurship basics: register the business, keep separate business and personal money, track cash flow, and quote profitably rather than matching the cheapest competitor.

Complaint handling: listen fully, acknowledge the problem, agree a remedy and a date, then follow up to confirm satisfaction.

Health and safety duty to customers: do not release a vehicle with loose trim, unsecured battery or uncured paint that could injure or fail.