Common Coating Terms

The following is a list of common terms and acronyms used in the powder coating and finishing industries.

Abrasion: The act of wearing, grinding, or rubbing away the surface of an object by friction.
Abrasive: A specialized material such as aluminum oxide, flint, garnet, sand, silicon carbide, or steel grit used for surface treatment.
Additive: A substance added to a mixture to provide or improve desirable properties or suppress undesirable properties.
Adhesion: The force that holds together molecules of substances whose surfaces are in contact or close proximity.
Adhesive Strength: The magnitude of attractive forces acting between a coating and substrate.
Adsorb: To take in solely on the surface.
AHJ: Authority Having Jurisdiction, the technical term used to describe a code inspector.
Air Feed: A spraying process in which an air stream carries the powder coating media to the surface being coated.
Alkaline Wash: A process that employs a high pH solution to clean parts that have limited build up of contaminants.
Aluminum Oxide: A particulate blasting medium used to clean and roughen surfaces that are to be coated.
Average Particle Size: The average diameter of powder particles as determined by various test methods.

Back Ionization: A condition occurring during electrostatic powder application in which an excessive buildup of charged powder particles prevents additional powder from being deposited on the substrate. It may also be referred to as electrostatic rejection. (See Faraday Cage Effect.)
Base Material: The surface being coated (See Substrate).
Binder: A polymer that acts as an adhesive to join elements of matrix coatings.
Blasting: A method of surface preparation involving cleaning or surface texturing by a projected stream of airborne abrasive particles.
Bond Coat: A preliminary layer of applied material that improves adherence of the subsequent spray deposit; a primer.
Bond Strength: The force required to pull a coating free of the substrate it is applied to.
BTU: British Thermal Unit, a unit of measure for heat energy that is commonly used when discussing the output of a curing oven’s heat system.
Burn-Off: A method used to remove existing powder coating that has already been cured in place. The substrate’s temperature is elevated above the degradation point of the coating and maintained until the coating breaks down.

Cartridge Filter: A cylindrical air filter unit used to separate powder coating media overspray from the air for recovery and possible reuse.
CFM: Cubic Feet per Minute, a unit of measurement for air volume that is commonly used when discussing the airflow of a blasting device, curing oven, fluidized bed, powder gun, spray booth, or other devices that rely on air movement.
Coating: The act of applying and building a deposit of coating media on a substrate. This term can also be used to describe the applied deposit itself.
Code Compliant: The term used to describe a device or process that meets the standards set forth by a particular organization. Code compliance is critical for safe, successful operations.
Code Inspector: An individual who is tasked with making sure that devices or processes meet set standards and has been granted certain enforcement powers within the area of his or her jurisdiction. Formally known as an AHJ (Authority Having Jurisdiction).
Conductor: Material that can support the flow of electrical current
Corona Charge: An electrostatic charge induced on powder coating media by passing the powder particles through an electrostatic field generated by a high-voltage device such as a powder gun.
Corrosion: The process of metal decomposition in which metal ions join with oxygen to form metal oxides. Also known as oxidation.
Crosslinking: A quality of thermosetting plastic resins in which polymer chains combine during the curing process. Typically, the greater the crosslinking, the tougher and more chemically resistant the coating will be after curing.
Cyclonic Exhaust: A type of media recovery unit that relies on a centrifugal process to separate airborne particles from the air.
Curing: The process of bonding or fusing a coating to a substrate with heat. Also used to describe the process of developing specified properties in the coating material as a result of exposure to heat.
Curing Schedule: The combination of curing temperature and curing time required to cure a coating.
Curing End Point: The point that occurs during or following the curing process at which the coating media is determined to have developed specified properties.

Defect: An unintentional feature or features that, alone or by accumulated effect, will render a component unable to meet set minimum acceptance standards or specifications.
Degrease: To remove oil, grease or wet lubricants from the surface of the substrate.
Dip & Spin: A coating application technique in which parts are placed in a basket that is placed in a coating bath, then removed and spun to remove excess coating media.
Dry Blending: A powder coating media manufacturing process in which materials are blended without melting.

Edge Coverage: A coating’s ability to flow over, build on and adhere to sharp angles, corners and edges.
Elastomers: A class of elastic substances resembling rubber.
Electrostatic Fluidized Bed: A device that charges fluidized powder so that it is deposited onto a substrate (usually grounded) that is placed in or passed over the device’s workspace.
Electrostatic Spray: Using a device to charge and propel a coating so that it is deposited on a substrate (usually grounded). A spray application process in which the coating media and the part to be coated are oppositely charged.
Environmental Regulations: Federal, state or local laws, statutes or regulations (such as the Clean Air Act) designed to protect human health and the environment.
Epoxy: A flexible resin used in coatings and that is created by the polymerization of an epoxide.
Exhaust Booth: An enclosure in which air flows across the workspace before being exhausted to the outside atmosphere. The airflow is used to remove fumes, gases, or solid particles such as powder coating overspray. Usually called a spray booth or paint booth.
Exhaust Plenum: A box-shaped device that draws air across the workspace before exhausting it to the outside atmosphere. The airflow is used to remove fumes, gases, or solid particles such as powder coating overspray.
Extruder: A device used in the production of powder coating media that raises a powder mixture to its melting point and squeezes it out in a flat ribbon.

Faraday Cage Effect: The repulsion of charged powder particles because of a corner or other concave feature of the substrate. A charge builds at the entry area, preventing penetration by powder into the back of the cavity.
Fillers: Pigments and other solids used to alter the properties of a coating media or reduce its per-pound cost.
Film Formation: The formation of a continuous film of coating media over the substrate due to heated particles melting together.
Fines: The term used to describe material that has a smaller particle size than the primary material being discussed.
Flash Point: The lowest temperature at which a solvent will generate sufficient vapors to ignite in the presence of an open flame.
Flashing: A brief pre-curing process (often at lower temperatures than the final cure) evacuate solvents or liquid components prior to full cure. This helps prevent bubbling within the finished coating.
Fluidized Bed Coating: A method of applying powder coating media to an object by immersing it in a fluidized bed (a container in which powder is aerated until it takes on fluid-like properties) of coating media. Preheated objects may be coated by dipping them directly into the fluidized powder. In electrostatic fluidized bed coating, the object is usually unheated but charged and passed over a fluidized bed of powder media which has the opposite charge.
Fluidizing: The process of suspending powder coating media in a continuous stream of air, giving it “fluid” characteristics. With gun-based systems, this process is used to facilitate the uniform transfer of the powder to the application device.
Flocking: A deposition method where powder coating media is applied by spray to a substrate that has been heated above the melting point of the powder.
Fusion: The act of melting and flowing by heated polymer particles until they form a continuous film.

Gel Time: The amount of time required at a given temperature for a powder to be transformed from a dry solid to a gel.
Grit Size: The particle size and distribution of abrasive grains in blasting media. Typically described using Society of Automotive Engineers’ reference numbers, such as SAE G25.
Grounding: Being electrically connected to earth (such as by a conductive rod driven into the ground through the shop floor) or a consistent negative charge.
Gun: The common non-technical term for a powder spray application device, or powder gun.-
Gun Extension: The common non-technical term for the extension tube attached to the front of a powder gun to permit spraying within confined spaces or deep recesses. Also known as a lance.

Hot Coating: See Flocking
HVLP: High Volume, Low Pressure, a popular wet painting spray technique that uses low air velocity to increase transfer efficiency and reduce air pollution.
Hybrid Resin: A combination of two or more common resins that benefits from characteristics of each component.

Impact Fusion: When powder particles combine to form a solid mass during the delivery and application process.
Intercoat Adhesion: A coating material’s ability to adhere to previously applied coatings, such as primers or previously applied coating films.

Jamming Booth: An open-faced spray booth. Small parts can be “jammed through” without being placed inside an actual enclosure. They are moved in front of the filter area and an exhaust fan draws air over the part as it is sprayed. Also known as a spray wall or exhaust plenum.

KISS: Keep It Simple Stupid, a term used when a system or process could become overly complicated for no beneficial reason. For example, when a purchasing agent wants to buy a conveyorized coating line instead of just using a simple batch system that is more than adequate.

Liquid: When talking about wet painting, people sometimes refer to it simply as “liquid.” This differentiates it from powder coating, which uses a dry powder.

Matrix Coating: A coating media where some (usually soft) ingredients are enveloped in other ingredients (such as harder, more wear-resistant binders). Also known as resin bonded coating.
Melting Point: The temperature at which polymer particles will begin to melt and flow together.
Micron: As commonly used in the coating industry, is equivalent to 1/25th of a mil, i.e., 25 microns are equivalent to one mil of coating thickness, or one mil of coating thickness is equivalent to 25 microns.
Mil: A unit of measure, often used to describe the thickness of a coating, which is equal to one thousandth (0.001) of one inch.
Mill: A device used for the production of powder coating media that breaks up the melt-mix extrusion into powder particles of a determined average particle size.

Non-Electrostatic Deposition: Depositing powder onto a substrate that is heated above the melting point of the powder material. Two non-electrostatic methods are flocking and fluidized bed coating.
Nozzle: The discharge end of a powder coating gun or blasting system.
Nozzle Accumulation: When powder coating, this term describes when powder coating media becomes deposited on the inner surface and/or on the exit end of the nozzle, reducing the gun’s effectiveness.

Overcure: When the curing time, curing temperature or combination of both exceeds the parameters recommended by the coating media manufacturer.
Overcure Protection: When a coating media has been engineered so that it can withstand some degree of excessive curing time, excessive curing temperature, or a combination of both without a significant degradation of the finished coating.
Overspray: With powder coating or painting, this describes the excess spray material that is not deposited on the part being sprayed.

Partial Cure: A process that is sometimes utilized when multiple layers of coatings are to be applied. The first coat is incompletely cured, and then the second coat is applied and both are fully cured together. See “Flashing.”
Particle Size: The average diameter of a given powder or grit granule.
Particle Size Distribution: An evaluation of powder coating media determined by defining the particle sizes and quantities in a given sample.
Pass: A single progression of a spraying or blasting device across the surface of the substrate.
Pencil Hardness: A value based upon the ability of an applied coating to resist penetration and gouging by pencil lead of varying hardness. The hardness rating of the coating is equal to the classification of the first pencil that does not gouge the coating (such as 2B).
Pigment: Fine, insoluble substances used to impart color to coating media.
Plate flow: The distance a powder coating flows in the molten state prior to becoming a gel.
Plenum: A term used to describe a component of ovens and spray booths where pressurized air is held before being introduced to the workspace (such as the enclosure that feeds heated air into the ductwork of an oven) or exhausted air is held before being routed back to the shop or ducted to the outside atmosphere.
Post Cure: A secondary application of high temperature curing designed to enhance specific properties of the finished coating.
Powder Coatings: Finely divided particles of organic polymers, pigments and additives that are combined to make a dry coating media that forms a seamless film over the substrate it has been applied to after being exposed to heated curing.
Preheat: When heat is applied to the substrate before spraying it with paint or powder coating media. Often used in humid operating conditions to enhance performance.
Preheat Temperature: A specified temperature that the substrate should attain immediately before paint or powder deposition.
Pressure Spraying: Coating technique where the coating is delivered from a pressurized container to the spray nozzle under positive pressure.
Pretreatment: A general term for processes utilized for cleaning and conditioning of a substrate before it is coated. Appropriate pretreatment is critical for proper coating performance.

QC: Quality Control, the process of inspecting samples to evaluate the quality of a process, substance or device (with the intention of improving overall quality).

Reclaim: The collection and reuse of oversprayed powder coating media or spent blasting media.
Recovery: The process of removing non-deposited powder coating media from the air or spent blasting media from the ground prior to reclaiming it for reuse.
Resistance (electrical): The opposition offered by a coating to the passage of an electric current through it.

Salt Test: A test procedure that simulates the corrosive environment caused by exposure to road salt or marine spray.
Sand Blasting: The process of surface cleaning and roughening that provides texturing of the substrate’s surface to aid coating adhesion. Blasting media includes a variety of substances such as walnut shells. The medium must be chosen to match the substrate’s properties and the nature of any material on the substrate to be removed.
Siphon Spraying: A common technique for applying coatings, also known as “conventional air spraying.” The coating is drawn from a reservoir into an atomizing air nozzle and propelled toward the surface to be coated.
Solvent Degreasing: The removal of oil, grease, and other soluble contaminants from the surface of the workpiece by exposure to suitable cleaners.
Spalling: The unintentional flaking or separation of a coating after it has been applied.
Spray Booth: A specially designed enclosure in which paint or powder coating media is introduced, contained and possibly recovered during the coating process.
Spray Rate: The rate at which paint or powder coating media passes through a gun.
Spraying Sequence: The order in which different layers of coating materials are applied in a planned relationship, such as overlapped, superimposed, or at set angles.
Static Electricity: The buildup of a stationary electrical charge, particularly on powder coating media or a coated surface.
Step Mounting: The intentional overlapping of several workpieces so that one protects or masks one or more adjacent pieces during a blasting or spraying process.
Storage Stability: An assessment of the ability of a coating material to maintain uniform physical and chemical properties while in storage over an extended period of time.
Substrate: Any surface to be coated. This can include metals such as steel, cast iron, bronze, brass, aluminum, and stainless steel, as well as other materials that can be coated.
Surface Treatment: Conditioning the substrate to prepare it for coating by blasting, phosphate pretreatment, etc. May include the removal of previously applied coatings.
System Efficiency: The measurement of the combined efficiencies of all components in the powder coating system, resulting in a comparison of total material usage against the total amount of material entered into the system.

Thermoplastic: Plastic resin that softens when reheated after production and hardens when cooled.
Thermosetting Resin (Thermoset): A resin designed to undergo an irreversible chemical and physical change when exposed to heated curing. A plastic resin that cross links during the curing process so that it does not soften when reheated.
Transfer Efficiency: The amount of coating deposited on a substrate compared to the total amount directed at the part to be coated, typically expressed as a percentage (such as 58%).
Transportability: An assessment of a powder coating media’s ability to be moved in the air stream through tubing and ducts without incident.

Upper Explosive Limit (UEL): The highest point at which particles suspended in air will ignite if a source of direct ignition is introduced.

Virgin Powder: Powder coating media in its original package as shipped by the powder coating manufacturer. “Non-virgin” powder is powder that has been reclaimed or otherwise handled.
Volatile Content: The quantity of material, expressed as a percentage of the weight of a coating material, which is lost under specified conditions of temperature and time.
Volatility: The characteristics associated with vaporizing. The rate of volatility varies among substances.

Water Wash: Forcing exhaust air and fumes (typically from a spraying booth) through water so that the vented air is essentially free of oversprayed particles or fumes.
Workpiece: The object or surface to be coated.
Wrap: A characteristic of liquid and powder coatings in electrostatic application to adhere to areas of the substrate not in direct line of sight of the delivery–C system end point.term substrate.