Powder Coatings Glossary of Terms

2nd February 2011

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A

Abrasive A coarse material used in blast cleaning, such as sand, steel shot, glass beads or plastics.

Absorption Process of soaking up or assimilation of one substance by another.

AC Current Alternating electrical current.

Accelerator Catalyst. Material that accelerates the curing or crosslinking, a mixture of crosslinkers or resins.

Acicular Pigments Pigments whose particles are needle shaped.

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

Acrylic Resin A clear resin derived from polymerised esters of various acrylic monomers. Acrylics are used for automotive topcoats and in other applications where resistance to chalking with exposure to sunlight is important.

Additive Chemicals added to a powder coating to improve some properties, such as flow, gloss and texture control.

Adhesion Bonding strength. Molecular attraction to the substrate surface to which a powder coating 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 the 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.

Adsorption Process of attraction to a surface. Attachment. Retaining foreign molecules on the surface of a substance.

Aerosol Dispersing of a liquid into a gas, for spraying.

Agglomeration A clump of powder particles bound loosely together into clusters containing trapped air.

Air Classification Device used in powder coating manufacture to aid in particle size management.

Air, Compressed Air at any pressure greater than atmospheric pressure.

Air Hose A section of non-metallic tubing used to deliver compressed air for paint or powder application.

Air Receivers Tanks into which compressed air is stored from the air compressor. Receivers help eliminate pulsing in the discharge lines and also act as storage capacity during intervals when demand exceeds the capacity of the compressor.

Air Valve Control valve in an air system for setting volume and pressure.

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

Air Volume Measurement of air volume, in cubic feet or meters per minute.

Alkali Caustic, inorganic substances that share the characteristic of being strongly basic (high pH)(examples are Sodium Hydroxide or Caustic Soda).

Ambient Surrounding environmental conditions.

Amides Organic compounds. A structure sometimes used in curing agents in Epoxy powder coatings.

Amp (Ampere) A unit of electrical current flow. The current produced by one volt applied across a resistance of one ohm.

Anti Foam agent Material used in pre-treatment systems to reduce the tendency of the chemicals to foam.

Anti oxidant An organic compound added to coatings to retard oxidation and deterioration.

Application Process of applying a coating to a substrate.

Aqueous A water based material.

Arcing A discharge of built up electrical charge, often forming a spark to a point of lower charge or earth.

ASTM The American Society for Testing Materials

Atom The smallest unit of an element that still possesses the properties of that element.

 

Atomisation The distribution of powder particles with air to form a fine pattern during the spraying application process.

Atomising Air Air injected into the powder path to atomise it into a pattern.

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B

Back Ionisation A condition, which may occur during electrostatic application of powder coating where excessive build up of charged powder particles limits further powder to be deposited onto the substrate. A pockmarking pattern usually occurs on the powder surface.

Bell Electrostatic spray device whose applicator is bell shaped. Centrifugal force throws the powder off its edge into a fine pattern. The charged particles are then attracted to the work surface.

Binder The portion of the powder formulation that forms the primary strength of the film. It binds pigments and additives into a solid film and to the substrate.

Blast Cleaning Removal of surface contamination and corrosion products by use of air and mechanical abrasives.

Blistering Bubbles formed under the cured powder film, usually caused by the expansion of trapped air, moisture or corrosion.

Blooming A hazy appearance on the surface of a coating.

Bridging The ability of a finish to cover cracks, voids or small gaps without a break in the film.

BTU British Thermal Unit. The amount of heat required raising the temperature of 1 pound of water 1 degree F.

Bulk Density Mass per unit of volume in powder form, including the air trapped between the particles.

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C

Caking Agglomerations of powder on fluid bed walls or components of the powder delivery system.

Calorie Quantity of heat that will raise the temperature of 1 gram of water from 14.5 to 15.5oC.

Cartridge Booths A type of recovery booth that incorporates a cartridge filter system to collect overspray powder.

Catalyst A special chemical that promotes the curing reaction.

Cavitation Failure of a powder to flow into the intake of a feed system.

CFM Cubic Feet per Minute.

Chalking Surface loss of colour and gloss in a coating from degradation of the binder by the UV components in sunlight.

Chipping The breaking away of small portions of a paint film due to the inability of that film to flex under impact, thermal expansion or the contraction of the surface.

Cissing Crating, round imperfections in the surface of the film, often caused by oil or silicone contamination.

Cleaner Detergent, alkali, acid, solvent or any other material used to clean and degrease before the application of a coating.

Clearcoat An un-pigmented coating. Can be a protective coating over a coloured or metallic basecoat or metal (example – brass).

Colour Fast Non fading. The ability to maintain colour under specified conditions.

Compatibility The capacity of powder coatings to be mixed and applied so as to show no visible, mechanical or any other detectable effect.

Composition Formula, make up, analysis. A specific combination of ingredients.

Compressor Machine design for compressing air or gas from an initial intake pressure to a higher discharge pressure.

Condensation A formation of water molecules due to drastic temperature difference between two surfaces.

Contaminants Foreign materials such as dirt, dust or oil that can be detected in the cured powder film.

Continuity Pinhole free film. A surface free from any defects.

Contrast Ratio A value related to the hiding power of a coating. The ratio of reflectance of the coating over black and white backgrounds at equal film thickness.

Conversion Coating Inorganic pre-treatment for metal substrates that prepare the surface for coating.

Co-polymer Large molecules resulting from the simultaneous polymerisation of two or more monomer units.

Corona An area of ionised air formed by a discharge of electricity.

Corona Charging The process of introducing a static electrical charge on powder particles by passing the powder through an electrical field generated by high voltage.

Corrosion Decomposition or reaction of metal with oxygen, water or other chemicals.

Cracking Splitting or disintegration of a powder film with breaks penetrating through to the substrate.

Cratering Small round depressions in a powder film.

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

Cross Contamination A condition when two or more powders are mixed by accident usually reducing quality.

Cross Hatch Test to determine adhesion.

Cure The reaction between resin and hardener to form the final film properties.

Cure Agent Hardener or crosslinkers.

Cure Oven Heated chambers for the purpose of stoving the powder coating.

Cyclone A cylindrical devise that separates powder particles from air. The system works by centrifugal spinning the particles around its perimeter, the powder is collected at the bottom and the air extracted from the top.

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D

DC Current Direct electrical current.

Decorative Coating A coating designed primarily for cosmetic and secondary for protection.

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

De-ionised Water Water containing no ions other than hydrogen, oxygen and hydroxyl ions. Usually produced through the use of ion exchange resins and used for the final rinse in pre-treatment processes.

Delamination Separation between two layers of coatings or between coatings and substrate.

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

Detergent An alkali or ionised cleaning or emulsified agent.

Dew Point Temperature at which water condenses from air at atmospheric pressure. Dew point varies with relative humidity.

Diffuser A porous material used in an airline to evenly distributes the air.

Dispersion Suspension of one substance in another.

Dry Blend Material generally added into the final coating as a dry additive without any melting.

DFT Dry Film Thickness. Depth of applied coating before curing.

Dry Flow The properties of a coating powder that relates to the ease of movement or transportation with air or vibration.

Dry Flow Additive An additive that improves the properties of the coating in the powder state. It improves the free flowing characteristics along with the sieving.

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E

Edge Coverage The ability to flow over, build and adhere to the sharp corners, angles and edges of components.

Elasticity The ability to recover from stretching.

Electrode A metal filament within or at the end of a powder spray gun used to create air ions at high voltage to produce charged particles.

Electrostatic Deposition A technique of moving and charging powder so that it is deposited on an earthed substrate.

Electrostatic Fluid Bed A fluid bed equipped with an electrode grid to charge powder so that it is deposited on an earthed component.

Epoxy A type of powder coating manufactured using epoxy resins, generally having high mechanical strength and corrosion resistance. But limited in gloss and colour retention when exposed to sunlight.

Epoxy Resin Film forming binder usually made from Biphenyl-A and Epichlorohydrin. Characterised as a Polyether.

Erosion Wearing away of a coating to expose the substrate.

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

Explosion Vent Pressure relief membrane to prevent damage to a confined dust collection device.

Explosion Limit Range of the ratio of powder particles to air which the mixture will explode or ignite.

Extender Pigment that can contribute specific properties to a coating, but usually does not substantially affect the colour.

Extruate Molten powder coating formulation as it exits the extruder during the manufacture process.

Extruder Device used to melt mix plastics and powder coatings. An extruder utilises heat and mixing to mechanically knead the formulation to achieve a homogeneous mixture.

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F

Fading Gradual Loss of colour, due to a chemical or physical change, usually caused by UV light.

Fan Pattern Geometry or shape of the spray pattern.

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

Fatty Edge Thick film sometimes found on heavy coated work, resulting in a rounded thicker coating on (usually) the lower edge.

FDA Federal Food and Drug Administration.

Feed Hopper A container that holds the powder for the supply to the guns. Often designed to be fluidised.

Ferrous Contains iron.

Filiform Corrosion Corrosion or crepe resembling a tread like structure under the coating, usually from a point of film breakdown or damage. Caused by poor or lack of pre-treatment.

Filler Extender, bulking agent or inert pigment.

Film Integrity Degree of continuity of a paint film.

Film Thickness Depth of cured coatings, usually in microns or thousands of an inch.

Film Thickness Gauge Instrument for measuring film thickness.

Filter Extender, bulk agent or inert pigment.

Fines Small powder particles. Usually under 10 microns.

Fish Eyes A large surface depression in a coating film often caused by contamination such as oil or silicone oil.

Flammable Easy to ignite, capable of burning with ease.

Flexibility Ability of a film to be bent without damage or cracking after application to a substrate.

Flip – Flop A characteristic of metallic coatings to change colour when viewed at different angles.

Flow Measurement of self-levelling. Characteristic of a coating allowing it to level into a smooth film of uniform thickness during the cure process.

Flow Additive Substance added to a formulation to minimise defects and produce a uniform film.

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

Fluidised Bed A container in which powder is suspended in a continuous stream of air.

Fusion The melting and flow of individual powder particles under the influence of heat to form a continuous film.

Fusion Point The temperature at which the powder is melted to form a liquid film.

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G

Galvanised Steel Steel coated with a layer of zinc.

Gassing Air or gas that escapes from a sub surface beneath a coating and causes blisters, eruptions or bubbles in the coating.

Gel Time Interval of time required at a given temperature for a powder coating to be transformed from dry solid to a gel like state. Measured in seconds.

Gloss The degree of reflection of light from the cured film.

Gloss Retention The ability of a coating to retain its original gloss.

Gravity Hopper A powder container, typically cone shaped design to force powder by gravity to feed a gun or transfer system.

Grinder Device used to crush or pulverise plastic or solid coating to powder form.

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H

Hardener Curing agent for thermosetting powder coatings.

Hardness The ability to withstand indentation and damage.

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

High Voltage Cable A specially designed cable that carries high voltage from generator to gun.

High Voltage Generator An electrical power transformer that converts 220 – 250 volts AC current to high voltage DC.

Hoes Flexible tube used to convey either powder from hopper to gun or compressed air to gun.

Humidity A measure of the amount of moisture in the air.

Hybrid An epoxy polyester powder coating product.

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I

Immiscible Incapable of being blended.

Impact Fusion The tendency of finely divided powder to combine with other particles in the application equipment creating a hard crust.

Incompatibility Inability to mix two powders without getting a different surface appearance, such as gloss reduction or craters.

Infrared Cure A method of curing powder using direct exposure to light energy.

Inhibitor Pigments Pigments that retard to corrosion process in the substrate.

Insoluble A substance that will not dissolve in water or solvent.

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

Intercoat Adhesion The ability of a powder coating to adhere to a previously applied film.

Iron Phosphating Conversion coating. Chemical deposition on steel for promoting corrosion protection and improve adhesion.

Isocyanate Resin Urethane resins. Isocyanate curing agents which when heated or reacted with hydroxy functional polymers giving urethane coatings.

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L

Levelling Ability of a film to flow out to a smooth uniform thickness.

Low Film Build Thin coating of powder.

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M

Mandrel Bend Test Physical bending test for evaluating flexibility of a coating.

Masking Covered area of a part to prevent coverage by powder during application.

Masking Tape An adhesive tape made for easy application and removal to mask areas where coating is not to be applied.

MSDS Material Safety Data Sheet.

Material Utilisation The percentage of powder that actually is deposited on the parts.

Maximum Loading Density The maximum number of parts that can be loaded onto a conveyor to ensure maximum powder utilisation.

Melt Mixing A predominant process for the manufacture of powder coatings involving continuous compounding of pigment, resin, fillers, additives and hardeners, mixing at elevated temperature.

Melting Point The temperature at which a finely divided powder will begin to melt and flow.

Metamerism A visual characteristic that describes a coating that appears different in colour when viewed under different lights.

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

Mileage A Term used to describe the area covered by a given amount of powder, usually measured in Meters per Kilo.

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

Miscible Capable of mixing or blending.

Misses Voids in the cured coating.

Molecule The smallest particle of a substance that can exist and still retain the properties of that substance. Molecules consist of two or more atoms.

Monomer A molecule that can be chemically bound as a unit of polymer.

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N

Non-ferrous A material containing no iron.

Non-flammable Will not burn.

Non-volatile Solid. Will not evaporate.

Nylon Thermoplastic powders coating that contains long chain polymers consisting of recurring amine groups (CONH). These coatings are tough, abrasive resistant and exhibit good chemical resistance.

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O

OEM Original Equipment Manufacturer.

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

Ohm A unit of electrical resistance.

Opacity Ability to hide the substrate at a given film thickness.

Orange Peel A wavy irregularity in the surface of a coating film created by the flow characteristics. Orange peel appears as an uneven or rough surface to the eye, but usually feels smooth to the tough.

Organic Substance containing carbon components.

Oscillator Device for moving automatic guns in a vertical plane to provide uniform and increased powder coverage.

Oven Chamber or enclosed area for the purpose of curing by heat or energy the coating.

Overbake Applying more heat or energy than is required to fully cure the powder coating. Overbaking can result in discolouration, loss of gloss or deterioration on mechanical properties.

Overspray Material that does not deposit on the component and goes to the recovery system.

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P

Particle Size The average diameter / size of particles supplied as a powder coating, following the grinding process.

PSD Particle Size Distribution.

Pass The motion of a spray gun in one direction only.

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

pH Value Measurement of acidity or alkalinity. pH 7 is neutral, Values greater than 7 are alkali less than 7 acid.

Phosphate To form a thin film of inert phosphate on the metal surface. Process to reduce the rate of corrosion.

Pigment Particles in a powder coating formulation that provides the colour, corrosion resistance and other properties.

Pinholes Formation of small holes through to the substrate. The appearance of fine pimply defects in a cured film.

Pinpoint Diffuser Powder gun tip, which yields a concentrated pattern.

Plastic One of many high polymeric substances, including both natural a synthetic rubber. At some stage in its manufacture or refinement every plastic is capable of flowing under heat and pressure to form its final shape.

Plastisol Film former containing resin and plasticiser with no solvents that forms a tough resistant thermoplastic coating.

Polyester A resin or powder containing the grouping R-COOC-R. The powder having excellent resistance to UV light.

Polyethylene Resin with the formulation CH2CH2 used in thick film thermoplastic powder coatings.

Polymers Poly = many: mer = units, Polymers are very large molecules built up by the combination of many smaller molecules, often having many thousand molecules.

Polymerisation Chemical reaction in which smaller molecules combine to form a high molecular weight polymer.

Polypropylene One of many polyolefin thermoplastics. Usually in exterior quality thermoplastic powder coating.

PVC Polyvinyl Chloride. Synthetic resin used in both liquid and thermoplastic powder systems.

Porosity Degree of integrity or continuity. A porous material will allow liquid or air to pass through.

Post Cure Heating of an object after application of the powder coating.

Post Heat Heating of an object after application of the powder coating.

Pourability The ability of a dry powder to flow uniformly or to be continuously poured from container at a steady flow.

Powder Booth An enclosure used for containment of powder coatings during the spray application.

Powder Segregation Stratification. Separation of powder particles (due to size) during the spray operation and recovery system. Due mainly to the forces of gravity, speed and electrostatic deposition.

Preheat Heating the component before the application of the powder coating.

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

Pressure Drop Loss in pressure usually due to length or diameter of piping or hose. Can be caused by blocked filters.

Pressure Gauge A gauge to determine the delivered pressure of a gas or fluid.

Pre-treatment The preparation of a part (component / substrate) prior to the coating to improve adhesion and corrosion resistance.

Primer A type of coating applied to the substrate surface to improve adhesion of a subsequent topcoat. To improve corrosion resistance, hiding power, surface smoothness.

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

Purging Cleaning one colour or powder formulation from all areas that come in contact with the powder coating before introducing a mew powder.

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R

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

Ratio Relationship in quantity or size between 2 things.

Reciprocator Device used to move automatic guns in a vertical plane. A reversing or reciprocating drive system provides motion.

Reclaim The process used to recycle non-deposited powder through the gun for reuse (after mixing and sieving).

Reclaim Powder Powder that has been oversprayed and collected for reuse.

Recoat The process of refinishing parts that have a surface defect from the first coat. Application of a second coat after correction of the defect in the first coating.

Recovery The process of removing non-deposited powder from air prior to re-cycling the powder through the delivery system.

Recovery System A filtration system that separates powder from the air stream to capture the overspray powder. Most common types are the cyclone or filter (cartridge) system.

Reflectance Degree of light reflected.

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

Resistivity The resistance to the flow of electrical current through a substance.

Respirator Safety breathing facemask.

Rework Process to correct imperfections or defects.

Robbing When powder is effectively redirected due to another earthed surface nearby.

Runs Sags in the coating. Can occur when objects are pre-heated.

Rust Corrosion on iron, Red oxide deposits on the surface of the metal.

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S

Sagging The downward flow of a paint or powder that is applied too heavy or onto a hot surface.

Salt Spray Test Corrosion test using salt laden moist air in an enclosed chamber, the air can be acidic.

Sand Blast Blast cleaning using sand or an abrasive to remove corrosion by impact.

Saponification * Alkaline hydrolysis of fats to make soaps.

* Test for coating resistance to an alkaline environment.
*
Hydrolysis of an ester by an alkali.

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 or the wire.

Soils Foreign matter on a part of the substrate to be cleaned in a pre-treatment system.

Solids Non-volatile portion of the coating material.

Solution Mixture formed when one material is dissolved into a liquid.

Solvent Liquid or blend of liquids used to dissolve or disperse paint. A true solvent is a liquid that can dissolve the paint resin.

Solvent Wash Cleaning using a degreasing solvent or mixture of solvents (often referred to as "gun wash")

Specific Gravity Sg. An expression of density of a material relative to the density of water (always classed as 1)

Specular Gloss Mirror like reflectance, gloss measured at a specific angle.

Spray Chamber An enclosure that surrounds the pre-treatment process and contains the spray cloud.

Spray Pattern Configuration of the spray leaving the powder gun.

Storage Stability The ability of the coating to maintain uniform physical and chemical properties subject to the manufacturers specification (time and temperature).

Stripper Chemical or mechanical method of removing the coating from the substrate.

Stroke A single pass with a spray gun in one direction.

Substrate The part being coated.

Surface Appearance Generally refers to the smoothness and gloss of the final cured film, and/or the presence of defects or contamination.

Surface Defects Flaws in the surface of the coated parts.

Surface Preparation Operations necessary to prepare the surface or parts prior to the application of the coating.

Surface Tension Cohesive force between liquid and solid (or Liquid and gas) surfaces.

Surfactant A chemical used to adjust the surface tension between two mediums.

Surge * A rise in pressure in an electrical circuit.

* A sudden burst of powder from a spray gun.

Suspension Mixture of fine particles of any solid with a liquid or gas.

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T

Tape Adhesion Test used to check for adhesion of a coating to the surface usually following a mechanical test.

Telegraphing Phenomenon that occurs when a surface defect on an un-coated part is visible in the final cured film.

TGIC Triglycidyl Isocyanurate. Hardener used in exterior quality polyester powder systems.

Theoretical Coverage The capacities of a given mass of a specific powder to coat in a cured state an area of substrate at a determined film thickness.

Thermocouple A pair of dissimilar metal wires that generates an electrical force at a point of contact that varies in proportion to temperature.

Thermoplastic A powder coating that will repeatedly melt when subjected to heat and solidifies when cooled.

Thermosetting A powder coating designed to undergo an irreversible chemical change during heating and will not revert to the liquid stage when reheated.

Threshold Limit Value Air concentration of chemical substances to which workers may be exposed to daily without adverse effect.

Throughput The production output or a system at a given line speed using a predetermined part or hanging pattern.

Tote Bins Large containers for shipping bulk powder coatings.

Toxic Poisonous.

Transportability A coatings ability to be carried in an air stream and passed through tubing and ducts designed to transport powder coatings.

Tribocharging The process of creating static charge on powder coating particles by friction against a non-conductive materials.

Triggering Intermitting squeezing and releasing of a spray gun trigger. Can cause surging in the powder equipment.

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U

Ultraviolet Radiation Light energy having a wavelength of about 0.4 – 80 milimicrons. Such energy can break certain chemical bonds and thus contribute to the fading and wearing away of a coating.

Undercured A coating that has not had sufficient exposure to the combination of heat and time to completely cure.

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V

Venturi A constriction in a powder pump that uses compressed air to lift and transport powder from feed system to the spray gun.

Virgin Powder Powder that has not passed through the recovery system.

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W – Z

Water Spotting Whitish spots on a pre-treated part where minerals in the water have been deposited.

Weather Resistance Capacity of a coating surface to resist the effects of weathering (UV light and water erosion)

Weld Splatter Beads of metal or flux left after welding.

Wrap A characteristic of a powder coating in electrostatic application to seek out and adhere to areas of the substrate not in direct line of sight.

Yellowing Development of yellow colour in pale colours when subjected to heat and/or light.

Zinc Phosphate Conversion coating used on steel and galvanised steel parts to improve adhesion and corrosion resistance.

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