Cert III Refinishing flashcards
Cert III Refinishing · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Isocyanate sensitisation
- An irreversible immune reaction to isocyanate hardeners in two-pack coatings. Once sensitised, a person may react to very low exposure, so supplied-air respiratory protection and booth containment are mandatory.
- Supplied-air respirator
- A respirator that delivers clean breathing air from a remote compressor through a hose to the hood or mask. It is required for spraying isocyanate-containing two-pack products because cartridge filters do not remove isocyanate vapour reliably.
- Lower explosive limit
- The minimum concentration of solvent vapour in air that will ignite. Solvent vapours are heavier than air, so extraction must be taken from low level to keep concentrations well below this limit.
- Booth filter pressure drop
- The resistance to airflow measured across booth filters. A rising pressure drop indicates loaded filters, which reduces airflow and can cause solvent entrapment, poor drying, and increased defect rates.
- Dry film thickness formula
- Dry film thickness equals wet film thickness multiplied by the volume solids fraction. A coating at 40 percent solids applied at 100 micrometres wet gives 40 micrometres dry.
- Two-cloth solvent wipe
- A cleaning method using one cloth wet with degreaser to lift contamination and a second dry cloth to remove the wet residue before it evaporates and redeposits oils on the surface.
- Silicone contamination
- Oil or silicone residue that causes craters and fisheyes in paint. It must be removed by washing and solvent wiping before abrasion, because sanding drives it deeper into the substrate.
- Abrasive grit sequence
- The ordered progression of abrasive grades from coarse to fine. Each step must fully remove the previous scratch pattern; skipping grades leaves deep scratches that show through the finish as sanding marks.
- Galvanised steel preparation
- Zinc-coated steel requires removal of the zinc passivation layer and use of a primer formulated for galvanised surfaces. Standard primers may fail to adhere and can react with the zinc coating.
- Aluminium conversion coating
- A chemical treatment that prepares bare aluminium for painting by creating an oxide layer that bonds to both metal and primer. Without it, primer adhesion to aluminium is unreliable.
- Adhesion promoter
- A thin tie-coat applied to plastics such as polypropylene and some bumper materials. It creates a bondable surface so the primer and topcoat adhere instead of peeling.
- Flex additive
- An additive mixed into coatings applied to flexible plastic parts. It keeps the film elastic so it flexes with the part instead of cracking when the bumper or panel deflects.
- Bare steel abrasive blast
- A cleaning method that removes mill scale and rust and creates an anchor profile. The profile depth must match the primer specification; too smooth a surface gives poor mechanical adhesion.
- Flash point
- The lowest temperature at which a liquid gives off enough vapour to ignite near its surface. It determines storage, handling, and ventilation requirements for solvents and coatings.
- Viscosity cup measurement
- A test in which the time for a fixed volume of coating to drain through a calibrated cup indicates viscosity. The reading is only valid at the product's specified reference temperature.
- Thinner addition rule
- Thinner is added in small measured increments with viscosity checks between additions. Overshooting viscosity requires more base product to correct and can reduce film build and sag resistance.
- Pot life
- The usable working time after a catalyst is mixed into a two-pack product. Material beyond pot life must be discarded, because gelled or reacted coating cannot be restored by thinning.
- Recoat window
- The time range during which a fresh coat can be applied without sanding. Beyond the maximum, the cured film must be abraded to give the next coat mechanical adhesion.
- Orange peel
- A textured surface resembling citrus skin, caused by poor atomisation, high viscosity, fast thinner, or excessive gun distance. Reducing viscosity and closing gun distance improve flow and levelling.
- Sagging
- Downward flow of excess wet coating before it sets, appearing as curtains or drips. Causes include over-thinning, slow passes, close gun distance, or too much wet film per coat.
- Solvent popping
- Small blisters or pinholes formed when trapped solvent escapes during baking or drying. Prevention is adequate flash-off time between coats and correct film thickness.
- Flash-off time
- The waiting period between coats or before baking, allowing most solvent to evaporate. Insufficient flash-off traps solvent, causing blistering, pinholing, and poor gloss.
- Gun distance
- The distance from the spray gun cap to the surface. Too far causes dry overspray and rough texture; too close causes runs, sags, and uneven film build.
- Spray pattern test
- A test spray on masking paper or card to check pattern shape, atomisation, and overlap before painting the vehicle. It confirms gun settings without risking the repair panel.
- Metamerism
- A colour match that appears correct under one light source but wrong under another. It results from pigment differences, so matching the original pigment system is required.
- Colour variant
- An alternate colour formulation for the same manufacturer code, used because factory colours vary between production batches and plants. Spray-out cards identify the closest variant.
- Spray-out card
- A test panel sprayed with the mixed colour and clear, then compared to the vehicle under controlled lighting. It is the accepted method for verifying a colour match before painting.
- Blend panel
- An adjacent panel onto which colour is faded to hide the repair boundary. The colour is applied in a decreasing taper, then clear is applied over the whole panel.
- Spectrophotometer reading
- An instrument measurement of colour expressed as numeric values. It narrows colour choice but must be confirmed visually, because instrument readings cannot detect metamerism.
- Basecoat coverage
- The number of coats needed to hide the primer or repair area. Applying thin, even coats with proper flash-off gives hiding without excessive film build or mottling.
- Clearcoat blending edge
- The zone where new clearcoat is melted or sanded into the existing finish. It must be prepared with fine abrasives and a blending solvent so the transition is invisible.
- Air line contamination
- Oil, water, or dirt carried by compressed air into the spray gun. It causes fisheyes and specks, so dryers and coalescing filters are required at the gun or booth inlet.