Powder Coating Troubleshooting Guide

Glossary of Industry Related Terms

Abrasion Resistance: The resistance of a cured coating to physical damage from scratching, abrasives in cleaners, or rubbing by contact with a hard object.

Achromatic Color: A neutral color with no hue.

Attribute: A distinguishing characteristic of appearance.

Back Ionization, Electrostatic Rejection, or Repelling: During electrostatic application, and excessive buildup of charged powder coating particles may limit further disposition of particles onto the substrate surface through reversal of the surface charge of the previously deposited particles.

Bulk Density: The mass required to occupy a specific unit of volume.

Channeling: Holes formed in the surface of the bulk powder as it is being withdrawn from below in the hopper.

Chemical Resistance: Tendency of a film to resist degradation upon exposure to various chemicals.

Chromatic: Color perception other than white, black, or gray.

Chromaticity: Two dimensional color specification, not involving illuminance, illustrated by pairs of numbers for dominant wavelength reflectance and purity.

CIE: International Commission on Illumination (Commission Internationale de L'Eclairage.

CIE Chromaticity Coordinates (x,y,z): The ratio of each tristimulus value of a color to the summation of the tristimulus values.

CIE Luminosity Function (y): A plot of the magnitude of the visual response as function of the visible light wavelength.

CEI L*A*B Uniform Color Space: Small color differences are measured by the Adams-Nickerson cube root formula.

CEI L*U*V Uniform Color Space: Associated chromaticity is measured through additive mixing of light.

CEI Standard Observer: A field of vision, typically 2 or 10, containing hypothetical tristimulus color-mixture data.

CEI Tristimulus Values: Amount of the tristimulus values required to match a perceived color in a trichromatic system.

Color Attribute: Color of an object defined in terms of lightness and chromaticity.

Color Difference: The difference in lightness and chromaticity of two colors measured under the same conditions.

Colorimeter: An instrument which measures color.

Color Measurement Scale: A numerical system defining the perceived attributes of color.

Color Specification: Numberical values of tristimulus, chromaticity, luminance, etc., defining a color within a particular color system.

Compatibility: The ability of two or more powder coating powders to be combined and applied to a substrate yielding no measurable difference in physical appearance and properties upon cure.

Corona-Charging: Induction of a static charge on powder coating particles by passing the particle through an electrostatic field created by a high voltage device.

Cross Hatch Adhesion: Adhesion of a cured film to a substrate is tested by scribing lines to produce 1/8 inch squares followed by the application of a specified pressure sensitive adhesive tape. After removing the tape, any coating lifted off or other damage to the squares is analyzed. Reference ASTM D-3359.

Cure End Point: The moment at which a powder coating film has developed its specified properties.

Cure Schedule: The temperature and dwell time required for a powder coating to achieve cure end point.

Cut Through Resistance: The ability of a curing powder coating film to resist penetration during application of a sharp edge, heat, and pressure.

Delivery: The system for which a powder coating is applied and cured.

Density: The ability of a material to absorb light (the darker the color, the higher the density).

Dry Blending: A process where materials are blended without the use of solvents or melt mixing.

Edge Coverage: An attribute of melted powder coating to flow and build film thickness at substrate edges, corner, and angles.

Electrostatic Deposition: The application of a charged powder coating onto a substrate with the opposite charge.

Electrostatic Fluidized Bed: The application of charged powder coating onto a grounded substrate as the substrate moves through a charged fluidized bed of the coating.

Faraday Cage Effect: An influence of a substrate's geometry where a field is generated, inhibiting electrostatic application of particle with insufficient mass to penetrate the field.

Flexibility: The ability of a cured film to bend without cracking or loss of adhesion to the substrate.

Flocking Disposition: The application of a powder coating onto a substrate which has been heated above the melt point of the powder coating.

Fluidized Bed: Powder coating particles are suspended, within a receptacle, emanating from continuous evloution of gas through the particles, reducing bulk density.

Fusion: The tendency of powder coating particles to melt, flow, and form a continuous film upon heating.

Gel Time: the time required for a thermoset powder coating to melt and advance to a gelled state at a defined temperature.

Hue: An attribute of color perception where a substrate is considered to be red, orange, blue, green, etc.

Humidity Resistance: The ability of a coating to maintain specified properties after exposure to a pre-designated environment of temperature and humidity.

Impact Fusion: Tendency for finely divided particles to combine with other particles within powder coating application equipment.

Impact Resistance: The ability of a coating to withstand rapid deformation. Also the degree of draw a coating that has been applied to a metal can tolerate.

Intercoat Adhesion: Adhesion which occurs between coating applied at different times.

Lightness: A perception which enables one to distinguish a light colored object from a dark colored object.

Mandrel Bend: A test for rating flexibility and toughness consisting of either cylindrical or conical mandrel. Coated panels are manually bent over mandrels of varying raii until cracking is apparent.

MEK Resistance: A chemical resistance test where a gauze soaked with a solvent, MEK (methylethyl ketone), then the saturated gauze is rubbed back and forth over two inches of the coating.

Melt Mixing: A process by which ingredients are mixed together in a molten state.

Melt Viscosity: The measure of the viscosity of a material or blend of materials at a specified temperature.

Metal Pretreatment: A process of substrate preparation consisting of surface cleaning, rinse, phosphatizing, seal rinsing, and drying. Pretreatment increases coating adhesion and resistance to salt spray and humidity.

Metameric: Colors formulated with different sets of pigments that match under one type of illumination yet do not match under a second type of illumination.

Micron: Unit of length equal to one millionth of an inch.

Nanometer: Unit of length equal to 10 to the -9 power.

Overbake Stability: The ability of a powder coating to withstand an extended bake schedule without the color and gloss deviating from the standard.

Particle Size: A discrete unit of size of powder coating particles created during the milling process. As a rule. the smaller the particle size, the greater the surface area.

Particle Size Distribution: Classification of particles of similar size based on the total population analyzed, i.e. 100%. Graphic or numerical representation relays the quantity of particles of similar size, the distribution.

Pencil Hardness: Abrasion resistance properties of a film are tested by forces applied to a substrate by lead pencils of varying degrees of hardness. Reference ASTM D-3363.

Percent Gloss: The amount of angular selectivity of reflectance responsible for the reflected objects being seen on the coating surface.

Plasma Disposition: Disposition of a powder coating, predominantly thermoplastic, where the powder is carried by a gas through a flame source, allowing disposition of molten powder onto the surface of the substrate.

Plate Flow, Inclined Plate Flow, Glass Plate Flow, and Pill Flow: The distance a molten powder coating composition will travel, due to gravity, prior to gelation.

Pourability: A characteristic of a dry powder to flow uniformly from a container at a constant rate.

Reclaim: A method where applied, non-deposited powder is collected for reapplication through the delivery system.

Recovery: A process where non-deposited powder is removed from the air before recirculating powder through the system.

Salt Spray Resistance: The ability of a coating to protect a substrate against corrosion.

Saturation: An attribute of color perception which differentiates migration from the gray of the same lightness.

Sintering: The tendency of a powder to agglomerate during storage.

Soil: The organic or inorganic contaminates on the surface of a substrate.

Specific Gravity: The ratio of the density of a substance to the density of a reference substance, typically water.

Standard: A reference for comparative measurements of color and other physical attributes.

Storage Stability: The ability of a material to maintain specified properties during recommended storage conditions.

Surface Appearance: The physical attributes which define the surface of a coating.

T-Bend Tests: An evaluation of flexibility where a coated strip of metal is bent around itself in multiple bends of 180°

Taber Abrasion: Abrasion resistance properites of a film are tested by forces applied to a substrate by an abrasive wheel. Reference ASTM D-4060.

Theoretical Coverage: The surface area of a substrate which a specific quantity of powder coating material will coat, as a function of specific gravity and coating thickness.

Thermoplastic: A polymer which repeatedly softens on exposure to heat and returns to its original condition when cooled to room temperature.

Thermoset: A polymer which irreversibly sets upon exposure to heat.

Transfer Efficiency: A ration or percent of powder deposited onto a substrate compared to the total amount of powder directed at the substrate.

Transportability: The ability of a powder to be transported through a system.

Tribo Charging: A deposition method where a powder particle generates a static charge by friction as the particles are transferred through a non-conductive material.

Tristimulus: Color values which indicate the amount of red, green, or blue receptors.

Virgin Powder: Powder which has not been applied through an application system.

Volatile Content: Tendency of amount of components of powder coating to pass into the vapor state at given time and temperature conditions.

Wrap: An electrostatic application phenomenon where charged particles are directed and adhere to the substrate away from the application point.