# Coating inspection glossary

Source: https://coatmentor.com/glossary/ · Updated 2026-10-04

109 terms in plain words. Follow a link for the full explanation.

Find a term

## A

**Abrasive**: Hard particles thrown at a surface to clean it and cut a profile: metallic (steel grit and shot) or non-metallic (slags, garnet, aluminium oxide). [More](https://coatmentor.com/standards/iso-11124-11127/)

**Adhesion**: How strongly a coating bonds to its substrate or to the coat below. [More](https://coatmentor.com/learn/adhesion-testing/)

**Adhesive failure**: In an adhesion test, a break between two layers or between the coating and the substrate. [More](https://coatmentor.com/standards/iso-4624/)

**Airless spray**: Spray application in which paint is forced at high pressure through a small tip and atomises without compressed air.

**Alkyd**: A binder that cures by oxidation with air. It is used for mild environments and maintenance painting. [More](https://coatmentor.com/learn/coating-types/)

**Amine blush**: A greasy, water-soluble film that forms on amine-cured epoxies in cold, damp conditions. It must be washed off before overcoating. [More](https://coatmentor.com/defects/amine-blush/)

**Anchor pattern**: Another name for surface profile. [More](https://coatmentor.com/learn/surface-profile/)

**Anode**: In a corrosion cell, the electrode that corrodes. [More](https://coatmentor.com/learn/galvanic-corrosion/)

## B

**Barrier coating**: A coating that protects mainly by keeping water, oxygen and ions away from the steel.

**Binder**: The film-forming part of a paint, which holds the pigment and bonds to the surface.

**Blast cleaning**: Surface preparation by abrasive thrown at high speed, graded Sa 1 to Sa 3 in ISO 8501-1. [More](https://coatmentor.com/learn/surface-cleanliness/)

**Blistering**: Raised domes in a coating filled with liquid or gas, often caused by salts or moisture under the film. [More](https://coatmentor.com/defects/blistering/)

**Blotter test**: A check for oil and water in compressed air: a white blotter held in the air stream (ASTM D4285). [More](https://coatmentor.com/standards/astm-d4285/)

**Bresle test**: A patch method that dissolves the soluble salts on a known area of steel so their amount can be measured (ISO 8502-6). [More](https://coatmentor.com/learn/soluble-salts/)

**Brush-off blast**: The lightest blast-cleaning grade: SSPC-SP 7 / NACE No. 4, close to Sa 1. [More](https://coatmentor.com/standards/sspc-surface-preparation/)

## C

**Calibration**: A check of a gauge by its manufacturer or a qualified laboratory, documented with a certificate. [More](https://coatmentor.com/standards/astm-d7091/)

**Cathode**: In a corrosion cell, the electrode that does not corrode. [More](https://coatmentor.com/learn/galvanic-corrosion/)

**Cathodic disbondment**: Loss of coating adhesion around a defect caused by the reactions of cathodic protection. [More](https://coatmentor.com/learn/cathodic-protection/)

**Cathodic protection**: Making a structure the cathode of a cell, with sacrificial anodes or impressed current, so it does not corrode. [More](https://coatmentor.com/learn/cathodic-protection/)

**Chalking**: A loose powder on a coating's surface, left when UV light breaks down the binder. [More](https://coatmentor.com/defects/chalking/)

**Cohesive failure**: In an adhesion test, a break within one layer of the coating. [More](https://coatmentor.com/standards/iso-4624/)

**Comparator**: A reference surface used to grade surface profile by sight and touch (ISO 8503-1, ASTM D4417 Method A). [More](https://coatmentor.com/standards/iso-8503/)

**Condensation**: Water that forms on a surface colder than the dew point of the air. [More](https://coatmentor.com/learn/dew-point/)

**Corrosion**: The deterioration of a metal by reaction with its environment.

**Corrosivity category**: The class of an environment in ISO 12944-2: C1 to CX in air, Im1 to Im4 in water and soil. [More](https://coatmentor.com/learn/corrosivity-categories/)

**Cratering**: Small round holes where wet paint pulled away from a contaminated spot. They are also called fish eyes. [More](https://coatmentor.com/defects/cratering/)

**Cross-cut test**: An adhesion test: a lattice of cuts through the film, then tape (ISO 2409, ASTM D3359 Method B). [More](https://coatmentor.com/standards/iso-2409/)

**Cure**: The process by which a coating film reaches its final properties, by chemical reaction or by drying. [More](https://coatmentor.com/learn/cure-and-recoat/)

## D

**Daily inspection report**: The inspector's dated record of readings, conditions, areas inspected and nonconformances. [More](https://coatmentor.com/learn/inspection-reports/)

**Dew point**: The temperature at which water vapour in the air condenses on a surface. [More](https://coatmentor.com/learn/dew-point/)

**DFT (dry film thickness)**: The thickness of a cured coating film. [More](https://coatmentor.com/learn/dft-measurement/)

**Dolly**: The test stud glued to a coating in a pull-off adhesion test. [More](https://coatmentor.com/standards/iso-4624/)

**Dry spray**: A rough, porous film made of paint droplets that dried before they reached the surface. [More](https://coatmentor.com/defects/dry-spray/)

**Dry to touch**: A drying stage at which the film no longer feels tacky. It is not yet cured. [More](https://coatmentor.com/learn/cure-and-recoat/)

**Duplex system**: A paint system applied over a metallic coating such as hot-dip galvanizing. [More](https://coatmentor.com/standards/astm-d6386/)

**Durability range**: The ISO 12944 planning figure for the time to first major maintenance: low, medium, high or very high. [More](https://coatmentor.com/learn/corrosivity-categories/)

## E

**Eddy-current gauge**: A thickness gauge for non-conductive coatings on non-ferrous metals such as aluminium. [More](https://coatmentor.com/standards/astm-d7091/)

**Electrolyte**: A medium that conducts ions, such as water or wet soil. Corrosion needs one. [More](https://coatmentor.com/learn/galvanic-corrosion/)

**Epoxy**: A two-pack coating that cures by chemical reaction. It is a tough barrier that chalks in sunlight. [More](https://coatmentor.com/learn/coating-types/)

## F

**Feathering**: Tapering the edge of sound coating around a repair so the new coats blend in.

**Flash rust**: Light rust that forms on wet-cleaned steel as it dries, graded light, medium or heavy. [More](https://coatmentor.com/learn/waterjetting/)

## G

**Galvanic corrosion**: Faster corrosion of the less noble of two different metals in electrical contact in an electrolyte. [More](https://coatmentor.com/learn/galvanic-corrosion/)

**Galvanizing (hot-dip)**: A zinc coating made by dipping steel into molten zinc (ISO 1461). [More](https://coatmentor.com/standards/iso-1461/)

**Glossmeter**: An instrument that measures specular gloss at 20°, 60° or 85° (ISO 2813). [More](https://coatmentor.com/standards/iso-2813/)

## H

**Hold point**: A stage at which work stops until the inspection is done and the work released. [More](https://coatmentor.com/learn/hold-points/)

**Holiday**: A pinhole, void or missed area that goes through the coating to the substrate. [More](https://coatmentor.com/learn/holiday-testing/)

**Holiday detector**: An instrument that finds holidays: low-voltage wet sponge or high-voltage DC spark. [More](https://coatmentor.com/learn/holiday-testing/)

## I

**Impressed current**: Cathodic protection driven by a power source through inert anodes. [More](https://coatmentor.com/learn/cathodic-protection/)

**Induction time**: A waiting time after mixing a two-pack paint, before application, where the data sheet asks for one. [More](https://coatmentor.com/learn/pot-life/)

**Inorganic zinc (IOZ)**: A zinc silicate primer that gives galvanic protection and cures by reacting with moisture in the air. [More](https://coatmentor.com/learn/zinc-rich-primers/)

**Inspection and test plan (ITP)**: The list of inspections and tests, their criteria, frequency, responsibility, hold and witness points. [More](https://coatmentor.com/learn/hold-points/)

**Intercoat adhesion**: The bond between one coat and the next. [More](https://coatmentor.com/defects/flaking/)

**Intermediate coat**: A coat between primer and top coat, mainly to build film thickness and barrier.

## L

**Lining**: A coating on the inside of a tank, vessel or pipe, often in immersion service. [More](https://coatmentor.com/learn/holiday-testing/)

## M

**Magnetic gauge**: A DFT gauge for non-magnetic coatings on steel: magnetic pull-off (Type 1) or electronic (Type 2). [More](https://coatmentor.com/learn/dft-measurement/)

**MEK rub test**: A cure test for inorganic zinc silicate primers: a cloth soaked in MEK rubbed on the film (ASTM D4752). [More](https://coatmentor.com/standards/astm-d4752/)

**Mill scale**: The blue-grey oxide layer formed on steel during hot rolling. Most coating systems need it removed. [More](https://coatmentor.com/learn/surface-cleanliness/)

**Mist coat**: A thin coat over a porous surface, such as inorganic zinc, that lets air escape before the full coat. [More](https://coatmentor.com/learn/zinc-rich-primers/)

**Mixing ratio**: The proportion of base to hardener in a two-pack paint, by volume or by weight. [More](https://coatmentor.com/calculators/mixing-ratio/)

**Mud cracking**: A network of cracks in a film applied far too thick, typical of inorganic zinc. [More](https://coatmentor.com/defects/mud-cracking/)

## N

**Nonconformance report (NCR)**: The record of work that does not meet the specification, closed only after the corrective action is verified. [More](https://coatmentor.com/learn/inspection-reports/)

**Nominal DFT**: The specified thickness of a coat. It is the reference value for ISO 19840 acceptance (CIP 2 and FROSIO only). [More](https://coatmentor.com/standards/iso-19840/)

## O

**Orange peel**: A dimpled film surface like the skin of an orange, caused by poor flow-out. [More](https://coatmentor.com/defects/orange-peel/)

**Overspray**: Paint droplets that miss the target or land partly dry on nearby surfaces. [More](https://coatmentor.com/defects/dry-spray/)

## P

**Pinholes**: Tiny holes through a coating film, often from air or solvent escaping from a porous surface. [More](https://coatmentor.com/defects/pinholes/)

**Pinpoint rusting**: Many tiny rust spots, often where profile peaks were not covered by the film. [More](https://coatmentor.com/defects/pinpoint-rusting/)

**Plural-component spray**: Equipment that meters and mixes two components at the gun, for fast-reacting products such as polyurea. [More](https://coatmentor.com/learn/pot-life/)

**Polysiloxane**: A durable, UV-stable top coat chemistry. [More](https://coatmentor.com/learn/coating-types/)

**Polyurea**: A very fast-curing two-pack coating sprayed as a thick membrane with plural-component equipment. [More](https://coatmentor.com/learn/coating-types/)

**Polyurethane (aliphatic)**: A two-pack top coat that keeps its colour and gloss in sunlight. [More](https://coatmentor.com/learn/coating-types/)

**Pot life**: The time within which mixed two-pack paint must be used. [More](https://coatmentor.com/learn/pot-life/)

**Pre-job conference**: The meeting before work starts where owner, contractor and inspector agree the specification, ITP and procedures. [More](https://coatmentor.com/learn/hold-points/)

**Primer**: The first coat of a system, applied to the prepared surface for adhesion and corrosion protection.

**Profile correction value**: The value subtracted from DFT readings on blasted steel under ISO 19840: 10, 25 or 40 µm for fine, medium or coarse. [More](https://coatmentor.com/standards/iso-19840/)

**Psychrometer**: An instrument with a dry and a wet bulb thermometer that gives relative humidity and dew point (ASTM E337). [More](https://coatmentor.com/standards/astm-e337/)

**Pull-off test**: An adhesion test in which a glued dolly is pulled off at right angles and the stress recorded (ISO 4624, ASTM D4541). Applies to CIP 2 and FROSIO only. [More](https://coatmentor.com/standards/iso-4624/)

## R

**Recoat window**: The minimum and maximum time before the next coat, from the data sheet, at a given temperature. [More](https://coatmentor.com/learn/cure-and-recoat/)

**Reference area**: A small area prepared and coated at the start of a job as the agreed standard for the rest of the work. [More](https://coatmentor.com/learn/reference-areas/)

**Relative humidity**: The water vapour in the air as a percentage of the most the air can hold at that temperature. [More](https://coatmentor.com/learn/dew-point/)

**Replica tape**: A compressible tape pressed onto blasted steel and read with a spring micrometer. The profile is the micrometer reading less 2.0 mils for the tape's backing. [More](https://coatmentor.com/learn/surface-profile/)

**Rust grade**: The starting condition of uncoated steel in ISO 8501-1, from A (adherent mill scale) to D (pitted). [More](https://coatmentor.com/standards/iso-8501/)

**Runs and sags**: Drips and curtains on vertical surfaces where too thick a wet film flowed down. [More](https://coatmentor.com/defects/runs-and-sags/)

## S

**Sacrificial anode**: A zinc, aluminium or magnesium anode that corrodes in place of the protected steel. [More](https://coatmentor.com/learn/cathodic-protection/)

**Safety data sheet (SDS)**: The supplier's document on a product's hazards, safe handling and emergency measures.

**Shop primer**: A thin primer applied to blasted steel in the shop to protect it during fabrication.

**Soluble salts**: Invisible chlorides and sulfates on steel that cause blistering and corrosion under a coating. [More](https://coatmentor.com/learn/soluble-salts/)

**Solvent**: The volatile liquid in a paint that dissolves the binder and evaporates as the film dries. [More](https://coatmentor.com/learn/volume-solids/)

**Solvent entrapment**: Solvent trapped in a film under a skinned surface, causing bubbles, popping or a soft film. [More](https://coatmentor.com/defects/solvent-entrapment/)

**Spot (SSPC-PA 2)**: The average of three or more DFT readings within a 4 cm circle. [More](https://coatmentor.com/standards/sspc-pa-2/)

**Spreading rate**: The area a litre of paint covers at a given DFT: theoretically 10 × volume solids % ÷ DFT in µm, in m²/L. [More](https://coatmentor.com/learn/volume-solids/)

**Stripe coat**: An extra coat brushed onto edges, welds, corners and bolts, where spray leaves less film. [More](https://coatmentor.com/learn/stripe-coat/)

**Substrate**: The surface a coating is applied to.

**Surface profile**: The peak-to-valley height of the roughness that blast cleaning leaves on steel. [More](https://coatmentor.com/learn/surface-profile/)

**Sweep blasting**: A light blast that cleans and roughens galvanized or coated surfaces without removing them (SSPC-SP 16). [More](https://coatmentor.com/standards/sspc-surface-preparation/)

## T

**Technical data sheet**: The manufacturer's document with a coating's properties and limits: solids, DFT, mixing, recoat times and temperatures. [More](https://coatmentor.com/learn/cure-and-recoat/)

**Thermal spray**: Molten zinc or aluminium sprayed onto blasted steel as a metallic coating (TSZ, TSA), usually sealed. [More](https://coatmentor.com/standards/iso-2063/)

**Thinner**: Solvent added to adjust viscosity. It adds volume but no solids. It changes the wet film needed. [More](https://coatmentor.com/learn/volume-solids/)

**Top coat**: The final coat of a system, chosen for appearance, weathering and UV resistance.

## U

**Ultrasonic gauge**: A thickness gauge that uses sound pulses, for coatings on concrete and other non-metallic substrates. [More](https://coatmentor.com/learn/dft-measurement/)

**Undercutting**: Corrosion that spreads under a coating from damage or an edge, lifting the film. [More](https://coatmentor.com/defects/undercutting/)

## V

**Verification of accuracy**: The user's check of a gauge against reference standards, at least at the start and end of each shift. [More](https://coatmentor.com/standards/astm-d7091/)

**Viscosity**: A liquid's resistance to flow. It changes with temperature and thinner.

**VOC**: Volatile organic compounds: the solvent part of a paint that air-quality rules limit.

**Volume solids**: The share of a paint's volume that remains as dry film. [More](https://coatmentor.com/learn/volume-solids/)

## W

**Waterjetting**: Cleaning with high-pressure water, graded WJ-1 to WJ-4. It exposes the existing profile but does not create one. [More](https://coatmentor.com/learn/waterjetting/)

**Wet film thickness (WFT)**: The thickness of a coating as applied, measured with a notch gauge straight after application. [More](https://coatmentor.com/standards/astm-d4414/)

**Wet sponge test**: A low-voltage holiday test for thinner films, up to about 500 µm (20 mils). [More](https://coatmentor.com/learn/holiday-testing/)

**Witness point**: A stage the inspector is notified of and may attend; work can continue if the inspector does not come. [More](https://coatmentor.com/learn/hold-points/)

## Z

**Zinc-rich primer**: A primer with enough zinc dust to protect steel galvanically: inorganic (silicate) or organic (epoxy). [More](https://coatmentor.com/learn/zinc-rich-primers/)

Also: [Concepts](https://coatmentor.com/learn/) · [Standards](https://coatmentor.com/standards/) · [Defects atlas](https://coatmentor.com/defects/) · [Glossary](https://coatmentor.com/glossary/) · [Calculators](https://coatmentor.com/calculators/) · [Guides](https://coatmentor.com/blog/).