Abrasion: Wearing, grinding, or rubbing away by friction.
Additive: A substance added to a formulation
in relatively small amounts to impart or improve desirable
properties or suppress undesirable properties.
Alkaline wash: Cleaning process that employs
a high pH solution (caustic). A good choice for parts with
little buildup of contaminants.
Aluminum oxide: Hard particulate medium
used in grit blasting to clean and roughen surfaces that
are to be coated.
Anodizing: Creating a hard oxide surface
on aluminum parts via an electrolytic process. Unsealed
anodized surfaces have a porosity that makes them excellent
substrates for coatings.
ASTM: American Society of Testing and Materials.
Average particle size: The average diameter
of particles as determined by various test methods.
metal: A soft alloy of tin, copper and antimony.
Back ionization: A condition occurring
during electrostatic application of powder in which an excessive
buildup of charged powder particles limits further powder
from being deposited on the substrate.
Binder: Tough polymer that acts as an adhesive
to join elements of matrix coatings.
Boundary lubrication failure: Condition
in which a lubricating film between sliding surfaces has
lost its hydrodynamic property due to heat, pressure or
Break-in: Initial wear of mechanical components
when large surface asperities can cause high friction and
Breakout: A violent or forceful break from
a restraining condition.
Brinelling: Surface fatigue of steel components
that undergo cyclic stress, which causes minute flexing,
resulting in work-hardening of the surface. Eventually,
brinelling may cause surface cracking or spalling.
Buffing: Process of polishing a cured coating
to improve release and low friction.
Bulk density: The mass per unit of volume
in powder form, including the air trapped between particles
Burn-off: A method of removing a coating.
Temperature is elevated above the degradation point of the
coating and held there until the coating breaks down. (See surface preparation).
Burnishing: Process of polishing a cured
coating to improve release and low friction.
Carrier: The liquid portion of a coating (solvent or water) in which
solids are dissolved or suspended.
Cloud-chamber technique: The method of
moving a charged or uncharged object through a charged or
uncharged cloud of powder in an enclosed chamber.
Coefficient of friction: A number expressing
the amount of frictional effect: static or dynamic.
Cold flow: Tendency of plastic materials
to migrate slowly under heavy loads and/or over time.
Compatibility: The capacity of different
materials from different sources or of different compositions
to be combined and applied so as to yield no visible or
mechanically measurable differences in the cured film or
Conductor: Material that can support flow
of electric current. Fluoropolymer coatings are normally
insulators, but can be modified with certain fillers and
pigments to make them conductive.
Contact angle: A means of quantifying the
nonstick properties of a coating by measuring the ability
of a liquid to wet its surface.
Corona charge: An electrostatic charge
induced on powder particles by passing them through an electrostatic
field generated by a high-voltage device.
Corona gun: A powder gun that uses corona
Corrosion: Process of metal decomposition
(oxidation) in which metal ions are united with oxygen to
form metal oxides. Fluoropolymer coatings provide excellent
barriers against corrosion.
Crosslinking: Quality of thermosetting
plastic resins in which polymer chains combine during the
curing process. In general, the greater the crosslinking,
the tougher and more chemically resistant the coating.
Cryogenic: Relating to very low temperatures.
Cure end point: The point either during
or following the cure schedule at which the coating film
is determined to have developed specified properties.
Cure schedule: The time/temperature relationship
required to cure a coating.
Curing: Process of bonding or fusing a
coating to a substrate with heat and developing specified
properties in the coating.
Cut-through resistance: A coating film's
resistance to penetration resulting from the combined application
of sharp edges, heat and pressure.
DFT: Dry Film Thickness.
Die-casting: Alloy casting process commonly
used to produce high volumes of intricate parts. The process
sometimes entraps small bubbles in the metal that can result
in "blow holes" when the coating is cured.
Dielectric strength: Ability of a coating
to resist the passage of electric current.
Dip/spin: Coating application technique
in which small parts are placed in a basket that is lowered
into a coating bath, then raised and spun to remove excess
coating. An economical system for coating high volumes of
Dry (solid) lubricants: Solid materials
such as PTFE, Moly Disulfide (MoS²) and graphite that
have low coefficients of friction.
Dry blending: A process for powder coating
manufacturing in which materials are blended without melting.
coverage: A coating's ability to flow over, build
and adhere to sharp corners, angles and edges.
Electrostatic spray: A deposition method
of spraying and charging a coating so that it is deposited
on a grounded substrate. A spray application process in
which the coating and part to be coated are oppositely charged;
process provides excellent "wrap" of coating around
the part, even on sides opposite the spray gun. (See Corona
Charge and Tribo Charging).
Engineering plastics: Plastic resins that
have high-performance properties such as high temperature
stability, hot hardness, abrasion resistance and corrosion
Epoxy: A flexible resin, usually thermosetting,
made by polymerization of an epoxide and used chiefly in
coatings and adhesives.
ETFE (ethylene tetrafluoroethylene): A
thermoplastic member of the fluoropolymer family. ETFE is
noted for exceptional chemical resistance, toughness and
cage effect: Repulsion of charged particles because
of the part's concave shape. Charges build at the entry
area, preventing penetration into the cavity.
FEP (fluorinated ethylene propylene): A
thermoplastic member of the fluoropolymer family. FEP has
excellent nonstick and non-wetting properties.
Fillers: Pigments and other solids used
to alter properties of coatings.
Flash point: The lowest temperature at
which a solvent will generate sufficient vapors to ignite
in the presence of flame.
Flashing: A brief sub-cure (at lower temperatures
than the final cure) to drive off solvents or carriers prior
to full cure. This helps prevent bubbling. See Partial cure.
Flocking deposition: A deposition method
of applying powder by spray to a substrate heated above
the melt point of the powder.
Fluidized bed coating: A method of applying
a coating to an article in which the article is immersed
in a dense-phase fluidized bed (a fixed container in which
powder is aerated) of powdered resin. Preheated objects
may be coated by dipping directly into the fluidized powder.
In an electrostatic fluidized bed the part is usually not
heated but is charged and passed through a fluidized bed
of powder which has the opposite charge.
Fluoropolymers: Family of engineering plastics
containing fluorine, characterized by high thermal stability,
almost universal chemical resistance and low friction.
Fretting: Wear or corrosion phenomenon
caused by vibration among tightly clamped or fastened surfaces
Friction (dynamic): Resistance to continued
motion between two surfaces; also known as sliding friction.
Friction (static): Resistance to initial
motion between two surfaces.
Fusion: The melting and flowing of heated
polymer particles to form a continuous film.
Time: The interval required at a given temperature
for a powder to be transformed from a dry solid to a gel.
Graphite: A carbon-based dry lubricant
that is preferred for high-temperature applications.
Grounding: Being electrically connected
to earth or having no charge.
hardness: Ability of a coating to retain hardness
and wear resistance at elevated temperatures. Usually a
characteristic of coatings based on thermosetting resin
HVLP (high volume, low pressure): A spray
technique utilizing high pressure in combination with low
air velocity to increase transfer efficiency and reduce
Hybrid resin: A combination of two or more
Hydrogen embrittlement: Embrittlement of
carbon steel caused by absorption of atomic hydrogen in
plating, pickling or acid cleaning processes.
adhesion: A coating's ability to adhere to previously applied films,
Kesternich: German scientist who developed the Kesternich Cabinet and
test method used for acid rain simulation (DIN 50018).
KN: Kilo-Newton (1 KN = 1,000 Newtons),
a metric measure of force, equivalent to "pounds force"
(lbf), (1 Newton = 0.225 pounds force).
lbf: Pounds force, a measure of force, also expressed
as "Kilo-Newtons" (KN).
Lower Explosive Limit (LEL): The lowest
percentage at which organic particles suspended in air will
ignite if a source of ignition is introduced. It is also
referred to as minimum explosive concentration (MEC).
coating: One in which some ingredients, such as
the lubricant (PTFE), which is soft, are enveloped in others
(the matrix, such as harder, more wear-resistant binders).
Also referred to as "resin bonded coating."
Melt point: The temperature at which a
polymer particle will begin to melt and flow.
Micro-inch: µ inch, a millionth of
Micron: µ, one micron, one millionth
of a meter. Also expressed as µm or micro-meter.
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.
Migration (of lubricant): Characteristic
of any lubricant which is under pressure to move away from
Mil: One thousandth (0.001) of an inch
(25.4 microns). Most common non-metric measurement of coating
Mill: A device that breaks up the melt-mix
extrusion into powder particles of a determined average
Moly, moly disulfide, molybdenum disulfide, MoS²: Four names for the same naturally occurring substance
that has good low friction and high load-bearing properties.
reduction: The absorption of sound vibrations. Fluoropolymer
coatings form good noise dampening surfaces.
Oleophobic: Oil shedding.
cure: Process sometimes utilized when multiple
layers of fluoropolymer coatings are to be applied. The
first coat is incompletely cured; the second coat is applied
and both are fully cured together. See Flashing.
Pencil hardness: A value determined by
measuring the relative hardness of a coating based upon
the ability of the coating to resist penetration and gouging
by pencil lead of varying hardness. The order of pencils
from softest to hardest is 4B, 3B, 2B, B, HB, F, H, 2H,
3H, 4H, 5H, 6H, 7H, and 8H. The hardness rating of the coating
is equal to the first pencil which does not penetrate and
gouge the coating when tested from softest to hardest.
PFA (perfluoroalkoxy): Thermoplastic member
of fluoropolymer family of engineering plastics, one characterized
by excellent release, low friction and toughness.
pH: An expression of the degree of acidity
or alkalinity of a substance expressed as a number from
0 to 14. Neutrality is pH7. Acid solutions are less than
7 and alkaline solutions are greater than 7.
Phenolic: A resin or plastic, usually thermosetting,
made by condensation of a phenol with an aldehyde and used
for molding, insulating, coatings and adhesives.
Phosphating: Surface pretreatment used
on ferrous parts that provide a very thin crystalline film
that enhances both corrosion resistance and adhesion.
Pigment: Finely divided, insoluble colored
substance used to impart color to a coating.
Plasma deposition technique: A method of
applying powder using compressed gas and melting the powder
in a flame before the powder impinges on a surface.
Plate flow: The distance a powder coating
flows in the molten state prior to the gel. Also referred
to as inclined-plate flow, glass-plate flow and pill flow.
PMT: Part Metal Temperature (in coil coating:
Peak Metal Temperature).
Polymer fume fever: An illness characterized
by temporary flu-like symptoms caused by inhaling the products
released during the decomposition of fluoropolymers.
Post-cure: A second cure at high temperature
to enhance specific properties such as release and non-wetting.
Postforming: Process of shaping parts after
a coating has been applied and cured, a technique commonly
used with stamped, blanked or spun parts.
Pourability: The ability of a dry powder
to flow uniformly or to be continuously poured from a container
at a steady rate.
Powder coatings: Finely divided particles
of organic polymers, pigments and additives alloyed to form
Powder metal: Material formed by compressing
particles of metal and heating (sintering) to solidify and
Preheating: Warming of parts prior to application
of a coating, recommended when adhesion is critical and
when parts are being coated in humid atmospheres. In some
cases, this technique can be used to achieve higher-than-normal
Preloads (for fasteners): The "tightness"
of a fastener, equal to the make-up energy applied minus
the energy required to overcome friction at the fastener's
bearing surfaces and threads.
Pressure spraying: Coating technique similar
to siphon spraying, except that the coating is delivered
from a pressurized pot to the spray nozzle under positive
pressure. Generally used for high-volume production.
Pretreatment: Processes for cleaning and
conditioning a substrate to be coated. Next to the choice
of coating, this may be the most important factor in the
use of high-performance coatings.
PTFE (polytetrafluoroethylene): A thermoplastic
member of the fluoropolymer family of plastics. PTFE has
the lowest coefficient of friction of any known solid and
the highest operating temperatures of the fluoropolymers.
PV, limiting PV (LPV) factor: Mathematical
limit of a coating's load-carrying ability and wear resistance
under bearing conditions.
PVDF (Polyvinylidene fluoride): High-molecular
weight thermoplastic of vinylidene fluoride with excellent
strength, wear resistance and creep resistance.
Reclaim: Collection and reuse of overspray powder.
Resistance (electrical): The opposition
offered by a coating to the passage of an electric current
fog: ASTM B-117 test procedure that simulates the
corrosive environment caused by road salt and marine spray.
Sand blasting (also grit blasting): The
process of surface cleaning and roughening that provides
a mechanical "tooth" to aid coating adhesion.
Media include aluminum oxide, even crushed walnut shells.
The medium must be chosen to match the substrate and the
foreign material on the substrate to be removed.
Sintering: A process where the temperature
of PTFE is raised to the point where PTFE particles soften
and form a bond with each other.
Siphon spraying: Most common technique
for applying coatings, also known as "conventional
air spray". The coating is drawn from a reservoir into
an atomizing air nozzle and propelled toward the surface
to be coated.
Static electricity: Buildup of stationary
electrical charge on a coating powder or a coated surface.
Stick-slip (chatter): Unstable sliding
condition in which movement of one part over another starts
and stops, caused by temporary overcoming of static friction.
Storage stability: 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, stainless steel, chromium and, with special precautions,
nickel. Paper, most plastics, wood, leather, fabrics and
glass can also be coated.
Surface appearance: The smoothness, gloss
and presence or lack of surface defects in a coating.
Surface treatment: Conditioning the substrate
before coating through grit blast, phosphate, etc. May include
the removal of a coating (See Burn-off).
(TFE): Monomer used as a chemical feedstock in
the production of PTFE.
Thermoplastic resin: A resin which will
melt when heated and solidifies when cooled, and softens
Thermoplastic: Plastic resin that softens
when reheated and hardens when cooled.
Thermosetting resin (Thermoset): A resin
designed to undergo an irreversible chemical and physical
change during a heat-cure schedule, i.e., a plastic resin
that crosslinks during cure so that it does not soften when
Transfer efficiency: The ratio of the amount
of coating deposited on a substrate compared to the total
amount directed at the part to be coated.
Transportability: A powder coating's ability
to be moved in the air stream through tubing and ducts.
Tribo charging: The process of creating
a positive static electric charge on powder particles by
action against a non-conductive material.
Tribo gun: A powder gun that uses tribo
Explosive Limit (UEL): The highest percentage at
which organic particles suspended in air will ignite if
a source of ignition is introduced.
powder: Powder in its original package as shipped
by the powder coating or resin manufacturer.
Volatile content: The quantity, expressed
as a percent weight of a coating, that is lost under specified
conditions of temperature and time.
Volatility: The readiness of a substance
to change from a solid or liquid form to a vapour.
Wear: Deterioration by friction (abrasion, spalling,
Weight solids: Expressed as a percentage,
it is the amount of a substance which remains relative to
the total weight, after all volatile components of the substance
have been evaporated. The determination is usually hastened
by heating the substance in a controlled environment.
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
system end point.