Abrasive - Coarse material used in abrasive blast cleaning, such as sand, grit, steel shot, or glass or plastic beads.

Acrylic - A powder coating with a significant content of a polymer containing short chain esters of various acrylic monomers.

Acrylic Resin - A clear resin derived from polymerized esters of various acrylic monomers. Acrylics are widely used as automotive and appliance topcoats and in other applications where resistance to chalking with exposure to sunlight is important. Physical properties can be controlled in part by choice of alcohol to make the ester.

Additives - Chemicals added to a powder coating to improve some property of a resin system such as flow control, gloss control, and texturing additives.

Adhesion - Bonding strength. Molecular attraction to the surface to which a substance is applied. A condition where one material is attached to another by means of surface attraction. Adhesion is affected by the condition of the surface to be coated, by closeness of contact, and molecular forces. The surface being coated should allow a certain amount of penetration, be chemically clean, be hard, not too smooth, and non-porous, to achieve good adhesion.

Agglomerate - A clump of powder particles bound loosely together into clusters containing entrapped air.

Air Cap/Nozzle - Perforated housing (at the head of a spray gun or nozzle) which directs compressed air against a coating material to form and shape it into an atomized cloud.

Air Velocity - Measurement of air speed, typically in feet per minute.

Air Volume - Measurement of air volume in cubic feet per minute.

Alkali - Caustic. Inorganic substances that share the characteristic of being strongly basic (high pH). (Example: Sodium hydroxide or caustic soda, lye, etc.)

Ambient - Usual or surrounding environmental conditions.

Anchor Pattern - Profile of a surface. Usually refers to surface profile after blasting.

Application - Process of applying a coating to a substrate.

Aqueous - A water-based material.

Arcing - A discharge of built-up electrical charge, often in the form of a spark, to a point of lower charge, usually ground.

ASTM - The American Society for Testing Materials, the source for voluntary consensus standards for materials, products, systems, and services.

B-staging - A process describing a powder coating material that has partially reacted or cured during manufacturing or storage.

Back Ionization - A condition which may occur during electrostatic application of powder where an excessive build-up of charged powder particles limits further powder to be deposited on the substrate and can reverse the electrical charge of the surface layer of powder particles. May also be referred to as Electrostatic Rejection and/or Repelling

Blast Cleaning - Removal of surface contaminate from a part by use of an air- or mechanically-propelled abrasive.

Blistering - Bubbles formed under a cured powder film, usually caused by the expansion of trapped air, moisture, or corrosion, either in a coating or in the substrate.

Blacked Isocyanate - A curing agent for hydroxyl-containing resins. Releases the blocked agent upon reaching an elevated temperature.

Bonding - Adhesion or secure joining of coating-to-coating or coating-to-substrate.

BTU - British Thermal Unit, the quantity of heat required to raise the temperature of 1 pound of water, 1 degree F, at a surrounding temperature of 39.2 degrees F.

BTUH - BTU's times hours.


Cartridge Booth - A type of powder booth that incorporates a cartridge filter system for powder overspray recovery.

Cartridge Collector - A self-contained unit with a cartridge filter housing or box for recovery of oversprayed powder that is used with a powder booth.

Catalyst - A special chemical that promotes the curing reaction.

Cleaner - Detergent, alkali, acid, solvent, or other cleaning material, often water- or steam-borne, used to clean and degrease parts prior to application of powder.

Clear Coat - An unpigmented powder coating applied over a color or base metal such as brass.

Coalescent Filter - A filter used in the compressed air line to fuse and trap liquid particles in the air stream.

Color Chip - Small piece of paper, celluloid, or other material, coated with finishing material and used as a color finish sample.

Compliance Coating - Coating which meets EPA defined standards for air, water, and waste disposal regulations.

Conversion Coating - Inorganic (zinc/iron phosphate) pretreatment for metal substrates that prepares the surface for powder coating.

Corona - A glowing, bluish or reddish area created by a discharge of electricity.

Corona Charging - The process of inducing a static electric charge on powder particles by passing the powder through an electrostatic field generated by a high voltage device.

Corrosion - Decomposition or reaction of metal with oxygen, water, or other chemicals, when exposed to a particular environment.

Counterflow - Transporting overflowed solution from one washer stage to another for reuse.

Cratering - Small round depressions on a paint film.

Creepage - Corrosion under a scribe line or edge after salt spray or other testing.

Cross Contamination - A condition when two or more powders are mixed by accident, usually resulting in a reduction in quality.

Cubic Feet Per Minute - Volume movement of a fluid. A measure used to size powder systems based on captive air. If not otherwise defined, the conditions are presumed to be air at a temperature of 68 degrees F, a pressure of 14.70 pounds per cubic foot. In gas industries, the temperature of standard air is usually given at 60 degrees F.

Cure - For thermoset powders, the polymerization of the resins and crosslinkers in the binder system to the desired molecular weight and physical properties of the coating, converting from a dry state to a solid continuous film.

Cyclone - A cylindrical device that separates powder particles from the air stream by centrifugally spinning the particles around its perimeter to the bottom for recovery. Some of the finer particles pass through the cyclone to a collector.


Decorative Coating - A coating designed primarily for cosmetic appearance and secondarily for protection. Decorative coatings are usually thin films (>5 mils).

Deflector - Conical shaped disc attached to the end of a powder gun to evenly distribute powder in a 360 degree pattern. Used to shape or direct the powder pattern.

Deionized Water - Water containing no ions other than hydrogen and hydroxyl ions. Usually produced through the use of ion exchange resins and used for rinsing parts after a seal rinse in a spray washer.

Delamination - Separation between two layers of coating or the coating and the substrate.

Delivery - The process of moving the coating powder through the application equipment to the end product. 

Discoloration - Color change.

DOI - Distinctness of Image. A test used to describe the surface reflectance of a paint film. A mirror would have very high DOI, but a low gloss texture would have no DOI.

Down-draft Booth - A powder booth in which the extraction opening is at the bottom of the booth.

Drag-out - Process of solution entrapment being pulled with the product typically out of a washer zone or coating enclosure.

Dry Film Thickness - Depth of applied coating powder before curing.


Edge Coverage - A coating powder's ability to flow over, build, and adhere to sharp corners, angles and edges.

Electrode - A metal filament within or at the end of a powder gun, used to create air ions as high voltage is applied. Powder is charged by the attachment of air ions.

Electrostatic Spray Technique - A deposition method of spraying and charging powder so that it is deposited on a grounded substrate.

Environmental Protection Agency (EPA) - Agency of the U.S. Government whose purpose is to regulate and control those agents affecting the environment.

Epoxy - A type of coating powder manufactured with epoxy resin, and generally having high mechanical strength and corrosion resistance but limited gloss and color retention when exposed to sunlight.

Etching - Surface preparation of metal by chemical process. Removal of a layer of the base metal.

Extruder - Device used to melt-mix plastics and/or coating powders. An extruder utilizes heat and mechanical kneading to achieve a homogeneous mixture.


Fading - Gradual loss of color of a paint film due to a chemical or physical change, usually caused by ultraviolet light.

Fan Pattern - Geometry or shape of spray pattern.

Fan Spray Nozzle - A powder gun tip that provides a fan-shaped spray pattern.

Faraday Cage Effect - A condition that may exist on a substrate due to its geometric configuration that may inhibit the electrostatic application of powder particles at that specific localized area, such as cavities or recesses.

Fatty Edge - Thick film sometimes found on heavily coated work, resulting in a rounded, thicker film along the edges.

Feed Hopper - A container that holds powder for supply to the guns. Most feed hopper designs employ fluidization of the powder for uniform feed to the guns. See Fluidized Bed.

Ferrous - Containing iron.

Filler - Extender, bulking agent or inert pigment.

Film Build - Cured thickness characteristics of the coatings.

Film Thickness - Depth of cured coating, usually expressed in mils, 1/1,000 of an inch.

Fines - Small powder particles, usually under 10 microns.

Fisheye - A large surface depression in a coating film often caused by a contaminant such as oil or silicone.

Flash Rusting - Very thin film of rust occurring within minutes after applying a pretreatment solution.

Flow - Measure of self-leveling. Characteristics of a coating allowing it to level or spread into a smooth film of uniform thickness before hardening. 

Fluidize - A term that describes powder that is in a state of suspension using compressed air, creating a fluid mixture of air and powder.

Fluidized Bed - A fixed container in which powder is suspended in a continuous stream of air. Preheated objects may be coated by dipping directly into a fluidized bed. The fluidized bed may also be used to facilitate transfer of powder materials to an alternate application site.

FPM - Feet Per Minute, a measure of air flow speed.


Galvanized Steel - Steel coated with a layer of metallic zinc.

Gassing - Air or gas that escapes from a sub-surface beneath a coating and causes blisters, bubbles or small holes in the coating. Gassing frequently occurs with zinc or aluminum castings or galvanized steel and is commonly referred to as out-gassing.

Gauge - Instrument or device for measuring, indicating or comparing a physical characteristic.

Gel Time - Interval required at a given temperature for a powder to be transformed from a dry solid to a gel-like state. Gel time is measured in seconds at a given temperature.

Geysers - Spouts of air and powder found in a fluid hopper when uneven air dispersion is applied.

Gloss - The degree to which a surface reflects light. Light striking a surface causes a portion of the light to bounce off the surface which is gloss, and the other portion of the light penetrates into the surface, where part of it is absorbed and then refracted and reflected. High gloss surfaces are typically very shiny.

Gloss Retention - Ability to retain the original gloss.

GPM - Gallons Per Minute.

Grounding - A method of removing or adding electrical charge.

Gun Extension - Extension adapter to a spray gun. Allows for better penetration for manual reinforcement.


Hardener - Curing agent for thermoset powder formulations.

Hardness - The ability of a cured coating to withstand indentation.

HEPA Filter - High efficiency particulate air-purifying filter. Separates particles down to sub-micron sizes from air.

Hexavalent Chrome - Chromium most often used as a seal rinse in a five- or more stage pretreatment system. Has a +6 valence Hex and is considered a reactive seal rinse.

Hiding Power - The extent to which a powder coating masks the color and pattern of the surface it is applied to at a given film thickness.

HVAC - Heating, Ventilating, Air Conditioning air supply system.

Hybrid - An epoxy-modified polyester or an epoxy-modified acrylic thermoset coating powder. Hybrids usually have good overbake and good application properties.

Hygroscopic - The tendency of a substance to attract or absorb moisture from the air.


Impact Fusion - The tendency of finely divided powders to combine with other particles in the application equipment during the application process.

Infrared Radiation - Electromagnetic energy in the infrared region of the electromagnetic spectrum.

Integral Charging - A powder gun that has a low voltage signal supplied to it and steps up the current to high voltage via a cascade multiplier located in the gun barrel.

Intercoat Adhesion - A coating powder's ability to adhere to previously applied films.

Iron Phosphate - Conversion coating. Chemical deposition on steel and aluminum for corrosion protection.

Isocyanate Resins - Urethane resins. Isocyanate curing agent which when heated or reacted with hydroxyl functional polymers, give urethane coatings.


Lance Extension - Variable extensions for powder guns.

Lower Explosive Limit (LEL) - The lower point for a range of concentrations or organic particles suspended in air which can be ignited by a sufficient energy source. Also referred to MEC or Minimum Explosive Concentration.


Magnehelic Gauge - Trade name of Dwyer Instruments' gauge for measuring air pressure in inches or water column.

Mandrel Bend Test - Physical bending test for testing flexibility. (ASTM Test D522)

Masking - Covering areas of a part to prevent coverage by powder during application.

Material Safety Data Sheet (MSDS) - Information supplied by coating manufacturers listing all known hazardous ingredients, physical and health hazards, first-aid procedures and protective equipment.

Material Utilization - The percentage of a volume of powder that actually is deposited on the parts, not lost through handling, transfer onto the racks, contamination or as non-reclaimed powder.

Matte - A surface with minimal reflection of light, the opposite of high gloss.

Melt Mixing - A predominant process for the manufacture of coating powders involving the continuous compounding of the pigments, fillers, catalysts and resins at elevated temperatures.

Mil - A measurement of film thickness, 1 mil = .001'.

Mild Steel - Structural steel or plate, malleable iron based alloy. SAE 1020, with a carbon content of up to 2.5%.

Mileage - Term used to describe the amount of area that can be covered with a given amount of coating material. Measured in ft2/lb.

Mill Scale - Oxide layer formed on steel by hot rolling process.

Molten Salt - Inorganic chemical or chemicals that are used at temperatures above their melting point as heat transfer, heat treating or metal cleaning purposes.

Molten Salt Bath - A specially designed vessel used to contain and heat molten salt processes.


National Fire Protection Association (NFPA) - An organization that has developed a system for indicating the health, flammability and re-activity hazards of chemicals.

Non-Ferrous - A material containing no iron.

Nylon - A thermoplastic powder coating which contains long-chain polymers consisting of recurring amide groups (CONH). These coatings are tough, abrasion-resistant and exhibit good chemical resistance.


OEM - Original Equipment Manufacturer.

Off-color - Not matching the color standard to which the coating is being compared.

Ohm - A unit of electrical resistance.

Opacity - Ability to hide the substrate of a given film thickness.

Orange Peel - A wavy irregularity in the surface of a paint film coated by the flow characteristics of the coating. Orange peel appears as a characteristically uneven or rough surface to the eye, but usually feels smooth to the touch.

Organic - Substance containing carbon compounds.

Organic Powder - That which was derived from carbon atoms containing compounds such as epoxies, polyesters, hybrids, vinyls, nylon, phenolics, etc.

Oscillator - Device used to move automatic guns in a vertical plane to provide uniform and increased powder coverage. Motion is provided by a wheel and arm mechanical device within the unit. Radial oscillators, or wagglers, move the guns in an arc motion.

OSHA - Occupational Safety and Health Administration; government enforcement agency for safety issues in U.S. industry.

Overall Efficiency - The product of the compression efficiency and the mechanical efficiency.

Overatomized - Powder that has been dispersed too finely but by use of excessive atomizing air pressure.

Overbake - Applying more heat in time and/or temperature than is required for cure. Overbake is the result of curing paint film at too high of a combination of time and temperature. The film often becomes too hard and may embrittle and/or color and gloss may be adversely affected.

Overspary - Material that does not deposit on the part of rack and goes to the recovery system.


Part Bring-up Time - Amount of time required to heat a part to a desired metal temperature.

Part Opening - The opening in the powder booth, ovens, washers and other equipment where parts enter and exit.

Particle Size - The average diameter of an object having irregular boundaries that can be determined to have diameter through various test methods.

Passivation - Conversion of a metal surface to a less reactive state. A process used to reduce the corrosion rate of metal surfaces.

pH Value - Measure of acidity or alkalinity. pH7 is neutral. The pH values of acids are less than 7. The pH values of alkali bases are greater than 7.

Phosphate - Chemical radical (PO4)-3. In coating operations, zinc, iron or manganese phosphate is used as a conversion coating to prepare the part for coating application.

Pigment - Particles in a powder formula that provide color, corrosion resistance and other properties.

Pinholing - Formation of small holes through the entire thickness of a coating. The appearance of fine, pimply defects in a cured film, due to air trapped under the surface of the film or other causes, resulting in small holes in the film.

Plenum - Air chamber used to transition or distribute airflow within a powder spray booth.

Polyester - A resin or powder containing the chemical group R-COOC-R.

Polyethylene - A thermoplastic resin with the formula (CH2CH2)x.

Polymers - Poly means many and mer means units. Polymers are very large molecules built up by the combination of many small molecules, often having many thousands of atoms.

Polymerization - Chemical reaction in which small molecules combine to form very high molecular weight molecules.

Polypropylene - One of the more common polyolefin thermoplastics. An addition polymer from propylene monomers with a crystalline structure (CH2CHCH2)x.

Polyvinyl Chloride - Synthetic resin used in solvent-type coatings; produced by polymerization of vinyl chloride. Also used in vinyl powders.

Porosity - Degree of integrity or continuity.

Post-curing - Heating of a part after powder coating to complete the cure cycle, which completes the cross linking of the components.

Power & Free Conveyor - Two-track chain conveyor system that allows product to be transported at different speeds and through different routes throughout the finishing system.

Powder - A coating blend made of non-volatile ingredients, applied dry and melted into a continuous film.

Powder Booth - An enclosure used for containment of powder during the spray operation.

Powder Coating - Coatings that are protective, decorative, or both, formed by the application of a coating powder to a substrate and fused into continuous films by the application of heat or radiant energy. Coating powders are finely divided particles or organic polymer which generally contain pigments, fillers and additives; and which remain finely divided during storage under suitable conditions.

Powder Room - A room that isolates the powder application process from the general plant environment. Sometimes referred to as Environmental Room.

Pressure - Force per unit area relative to atmospheric pressure. Usually expressed in pounds per square inch.

Pretreatment - The preparation of a part prior to the application of powder coating in order to improve adhesion and corrosion resistance.

Primer - A type of coating, usually paint, applied to a surface to improve adhesion of a top coat and/or improve corrosion resistance.

Primer Surfacer - Coating used to prime a surface as well as fill irregularities in the substrate. Primer surfacers are usually applied over a primer.

Production Rate - Measurement of square foot per day of the surface area cleaned or coated in one working day by one person.

Profile - Surface contour of a blast-cleaned surface as viewed from the edge cross-section of surface.

Profile Depth - Average distance between top of peaks and bottom of valleys on a surface.

PSI - Pounds per square inch, a measure of force above a vacuum.

Pump - Device which converts mechanical force and motion into hydraulic fluid powder.

Pump Screen - A screen that catches large contaminants in a process solution as the solution flows through it to the pump.

Purging - Cleaning one color or powder formulation from all areas that come in contact with the powder before introducing another color or powder.


Radiation Cure - Curing a coating by means of exposure to electromagnetic waves or particles such as infrared, ultraviolet or electron beam.

Reciprocator - Device used to move automatic guns in a vertical plane. Motion is provided by a reversing or reciprocating drive system.

Reclaim - The process used to recycle nondeposited powder through the delivery system for reuse.

Reclaimed Powder - Powder which has been oversprayed and captured for reuse.

Recoat - Process of refinishing parts that have a surface defect from the first coating application by repairing the defect and respraying.

Recovery - The process of removing nondeposited powder from the air prior to recirculating the powder through the delivery system.

Recovery System - A filtration system that separates powder from the airstrip with a fan that captures oversprayed powder and maintains negative air pressure inside a powder booth. Most common type of recovery systems are the cyclone system and the cartridge module system.

Resin - Any class of solid or semi-solid organic material of natural or synthetic origin, generally of high molecular weight with no definite melting point. Most resins are polymers.

Resistivity - The resistance to the flow of electrical current afforded by a substance.

Reverse Osmosis - Method of removing metal ions from an aqueous solution via semi-permeable membranes.

Rework - Procedures to correct powder coating imperfections or defects.

Runs - Sags in the coating.

Rust - Corroded iron. Red iron oxide deposited on metal. Also other metal oxides formed by corrosion.


Salt Spray Test - Corrosion test using salt (NaCl) solution sprayed as a mist in a heated humidity chamber to simulate seashore conditions, or to accelerate corrosion at a controlled rate. (ASTM Test B117)

Sand Blast - Blast cleaning using sand as an abrasive.

Sanitary Pan - A trough that is mounted under a conveyor chain to catch debris and keep it from falling on work in progress.

Scale - Rust occurring in layers, commonly found on hot-rolled steel.

Screen Mesh Size - The mesh number of a screen designates the openings per square inch using standard wire. Screens are used to classify the size of the coating powders.

Seal Rinse - A final rinse in a spray washer that passivates the pretreated surface to prevent oxidation and provide corrosion resistance in the field.

Seeding - Formation of small agglomerates or gel particles. Seeds in coating powders can form when the material is overheated during the extrusion process.

Shelf Life - Maximum amount of time a material may be stored and still be in usable condition.

Shot Blasting - Blast cleaning using steel shot as the abrasive.

Side-draft Booth - A powder booth where the air extraction opening is on the side of the booth.

Sieve - Powder particle classifier which utilizes wire mesh of various sizes to screen out oversized powder particulate and foreign material or dirt. (Rotary Sieve - Cylindrical screen equipped with an electrically driven paddle used to classify powders, or remove undesirable particulate from powder materials. Vibratory Sieve - Electrically or pneumatically driven screen utilizing vibration to classify powders, or remove undesirable particulate from the powder materials.)

Silicone - One of a family of polymeric materials in which the recurring chemical group contains silicone and oxygen atoms as links in the main chain. These compounds are derived from silica, i.e., sand, and methyl chloride. The various forms obtainable are characterized by their resistance to heat. Uses for silicone include: greases for lubrication; rubber-like sheeting for gaskets; heat-stable fluids; compounds for waterproofing and insulation; thermosetting insulation varnishes; and resins for both coating and lamination. [Silicone lubricants should not be used around a finishing system because it will cause defects in the finished surface.]

Sintering - The tendency of some powders and powder coating materials to agglomerate during storage.

Soils - Foreign matter on a part's substrate prior to being cleaned in a pretreatment system. Can be organic or inorganic.

Solvent - Liquid or blend of liquids used to dissolve or disperse a paint. A true solvent is a single liquid which can dissolve a paint.

Solvent-borne Coating - Coating containing only organic solvents. (Non-water-borne)

Specific Gravity - An expression of density of a material relative to water. Examples: water - 1.000; ammonia - .587; propane - 1.550; natural gas - .665. Ration of the weight of a given volume of liquid or solid to the wight of an equal volume of water. (ASTM Test D3451)

Specular Gloss - Mirror-like reflectance. Gloss measured at a specific specular angle. (ASTM Test D523)

Spray Pattern - Configuration of spray with a powder gun. See Diffuser and Fan Spray Nozzle.

Spray-to-waste Operation - Utilizing virgin powder only. All overspray powder is discarded and not recycled. 

Storage Life - Period of time that a powder material will remain usable in storage.

Storage Stability - The ability of coating powders to maintain uniform physical and chemical properties after being subjected to the manufacturer's specified storage conditions.

Substrate - The part to be powder coated.

Surface Defects - Flaws in the surface of a coated part.

Surface Preparation - Operations necessary to prepare the surface of a part prior to the application of a coating.

Surfactant - Chemical used to adjust surface tension of a material.

Surge - (1) A rise of pressure in an electrical circuit. (2) A sudden burst of powder from the spray gun.