Macro Defects in Steel - Glossary of Powder Coatings Terms

Glossary of Powder Coatings Terms

Additive
Materials added in powder production to optimize powder film for certain applications.

Adhesion
Sticking of the powder coating to the work piece; Mechanical anchoring and/or chemical connection between powder coating and substrate surface. Prerequisite is proper pretreatment.

Adhesive remnants
Remnants that are not removable by pretreatment cause these surface defects and adhesion problems.

Agglomeration
Powder which does not adhere to the work piece or does not get recycled, but rather piles in the booth.

Anodizing
Surface treatment for aluminum, establishment of a (colored) aluminum oxide layer and its subsequent solidification.

Application equipment
Equipment necessary for powder application, i.e. guns, charging equipment, nozzles, hoses etc.

Atomized air
To support spray cloud, also to help avoid sintering at the corona needle and deflector.

Atomizing air
Supplemental air to regulate amount of powder in the gun, higher supplemental air – less powder coating, smaller powder cloud.

Automation
Powder application in connection with automatic guns (permanently mounted on reciprocator or robotics).

Base material
Substrate.

Bonding agents
Main components of powder coatings, resins like epoxy, polyester, polyurethane or acrylic.

Booths
Cabinet for coating (steel, stainless, glass, plastics).

Bubbles
Elevations in the powder film caused by water, salt and oil remnants etc.

Bubbling
Gassing of the powder itself at high mil thickness (starting at 150 [µm] / 6 [mils]), especially with TIC-free powders and IR ovens).

Buchholz hardness
Test procedure to measure the resistance of powder coating surfaces against pointed pressure demands; DIN 53 153/ISO 2815.

Carbon
Burnt oil or grease on the work piece, burnt in through welding.

Chalking
Decomposition of the resin and bleaching of the pigments through UV light or chemical influence.

Charging
Electrostatic charging of the powder through corona or tribo method.

Chemical resistance
Resistance of the powder coat surface against various chemicals.

Cleaning
Cleaning of powder application unit during color change. A necessary evil of powder coating.

Coating system maintenance
Necessary regular servicing of the coating system by the system manufacturer.

Color
Perception transmitted by the eye, caused by light sources and light reflexes.

Color deviation
Difference in color from original sample to test part (color chart to work piece or work piece I to work piece II).

Color standard
Official color charts, which represent industry standards (RAL, Pantone).

Contamination
Dirt.

Conveyor halt
Materials added in powder production to optimize powder film for certain applications.

Corona charging
See e-static.

Corrosion
The reaction of a metallic work piece with its surrounding environment, which causes measurable changes affecting the function.

Crater
Surface defects, which reach through the powder film to the surface.

Cratering of Hammertone effects
Through insufficient grounding, development of star shaped voltage craters that expose the underlying surface.

Crosslinking
The setting up of chemical links between the molecular chains of a resin to form a three-dimensional network polymer system.

Curing
Complete fusing of the powder coat. Minimum time and temperature are required Cyclone
Device to return and circulate oversprayed powder. Always requires a final filter.

De-ionized water rinse
Final stage of pretreatment with salt free water (0 – 15 tds).

Development of stripes
Uneven film thickness caused by uneven sinus curve.

Dip pretreatment
Pretreatment for parts, not suitable for scoop shaped parts.

Dirt
Mainly contributes to reduce quality of coating (dust, fibers, shavings etc).

Distance I
Distance from gun to work piece.

Distance II
Distance between work pieces.

Dry-off oven
Oven (chamber) for drying parts after liquid chemical pretreatment.

Duration time
Time a coated part remains in the curing oven.

Edge deposits
Powder accumulation at the work piece edge.

Environmental conditions
Existing climate and environmental conditions in the coating area.

E-Static
Electrostatic charging of the powder particles in the area of corona discharge, whose voltage is produced by the electrode inside the gun or co conveyed by cable.

Faraday cage
A physical phenomenon – the area of a part where the electric field does not penetrate.

Filiform corrosion
Thread like development of metal hydroxides (not Al2O3)on aluminum surface, shows as thin threads with sharp edges under the powder coating.

Film (float)
Surfacing of additives in the powder coating, example OGF additive.

Film (haze)
Undesirable haze on powder coat surface.

Film thickness
Thickness of the powder coat.

Filter
Used to separate the powder-air-mixture (overspray) in reclaim system (plate, pocket or cartridge filters).

Final filter (purification filter)
Final filter in the coating system for micro particles, which are not eliminated by the reclaim system.

Fish eyes
Same as craters.

Flow
Smoothness of the powder coat film.

Fluidizing
Stirring of powder coating in the fluid container or powder storage box via pressurized air.

Fluidizing base
Air permeable sinter material in the powder storage container. Powder is fluidized through incoming air (0.3 – 0.5 bar).

Fresh water rinse
Rinse stage in the pretreatment system to rinse cleaning chemicals with fresh water.

Friction charging
See Tribo Charging.

Galvanized zinc plating
Application of an approximately 5 – 15 [µm] / 0.2 – 0.6 [mils] layer of corrosion protection (zinc) via electrolytical separation of watery, acidy or alkaline zinc electrodes.

Gas quality
Gas used to heat the dry-off oven and powder curing (natural gas, city gas, butane, propane). Heating value and blend are of essence.

Gassing
Ingredients in the substrate, which through melting of the powder on the surface escape (evaporation, air, gases etc.) can cause irregularities in the powder film.

Gel particles
Unopened resin particles in the powder coating.

Glass point
Transition phase of the powder – gelling.

Gloss
Reflection capacity of a surface, with powder coatings ranging from glossy to flat mat..

Graininess
Ingredients in the substrate, which Surface defects, elevations in powder film.

Grounding
Contact by work piece and coating system component with earth/ground.

Gun
Necessary for charging and application of powder coat (Corona charging and Tribo).

Hanging devices
For suspension of work pieces during the coating process.

Heat up speed
Time required to heat an object to required temperature.

Heater
For pretreatment and powder drying; gas and oil, direct/indirect, electric, IR.

Hiding power
Ability of the powder, given appropriate film thickness, to sufficiently hide the color of the substrate.

Hose
Comp. Transport hose.

Hot dip galvanizing (H.D.G.)
Corrosion protection- application of an approx. 30 – 80 [µm] / 1 – 3.2 [mils] thick zinc layer by dipping at high temperatures (approx. 400 [°C] / 752 [°F]).

Incompatibility
Condition of the surface through uncontrollable chemical reactions.

Infiltration
Development of corrosion through moisture and salts (osmosis) between powder coating and part.

Injector
Venturi pump for powder transportation.

Insulation of work pieces
Insufficient grounding, caused by excessive film thickness on parts and hanging devices.

Intercoat adhesion
Adhesion between first and second powder coat layer.

Ionization
Comp. e-static.

Lifting
Cured powder coating lifts from substrate under various types of mechanical stain (i.e. during deburring, cutting, milling).

Lubricants
Oils and greases used to help in gliding during forming of profiles in the manufacturing process.

Lumps
Clustering of powder coating in the box due to transportation, moisture influence, Corona charging or heat.

Material selection (powder coating)
Suitable powder coating (exterior vs. interior coating, special effects etc) for an application.

Material selection (substrate)
Suitable, coatable materials (steel, aluminum, glass) for the application.

Matting
Reduction of the gloss level, powder coating surface appears lower in gloss level.

Mechanical properties
Necessary properties of the powder coating (test according to ASTM, example: Conical bending or impact test, Erichsen cupping etc).

Metal shavings
Machining residues on parts (cutting, polishing, drilling etc).

Metallic pigments
Conductive or non-conductive effect producers in powder coatings.

Metallic powder coatings
Effect powder coatings with metallic appearing surface (pearl, glitter, Glimmer etc).

Metamerism
Color difference at varying light conditions.

Moisture
Absolute moisture content in a powder coating.

Movement of reciprocator
Spray pattern with reciprocating guns, influenced by conveyor speed and lift.

Nozzles
Various end pieces on the gun (powder bells, finger nozzles, round and flat type nozzles).

OGF-Additive
(OGF = Out-gassing Forgiving) Additive to help reduce out-gassing of the substrate in the powder film.

Oil remnants
Remnants of oil on parts, which were not removed by pretreatment (Lanolin, extrusion oil etc.).

Oil residues
Residues not removed by pretreatment.

Orange peel
Short or long ripple effect on the powder surface.

Oven types
Oven differences through construction and heating unit, i.e. chamber oven, conveyor oven, radiation oven, IR oven (comparable to heating, gas quality).

Over coating
A second layer of powder is applied.

Over curing
Temperature in the curing unit is too high, or time in the oven is too long..

Oversize particles
Powder particles that are larger than the screen size and are separated during straining.

Overspray
Powder coat that does not adhere to the surface during application.

Oxide layer
Corrosion residues on the work piece surface.

Particle distribution
Distribution of powder coat particles according to size and percentage.

Penetration
Ability to coat in to the corners, recesses and hollow areas.

Pickling
Caustic, watery cleaning procedure, which removes oxide layers, rust, ground in dirt and foreign materials.

Picture framing effect
Higher film thickness of the powder coating on the edges of the work piece, caused when current is too high at the edges, e.g. noticeable with fine textures and metallics.

Pigments
Coloring agents in the powder coating.

Pimple
Elevation in the powder surface.

Pin holes
Surface defect. Development of small pores in powder coating.

Polishing marks
Mechanical surface treatment. Can be visible through powder coats.

Powder
Dry, dust like thermosetting coatings.

Powder adhesion
See adhesion.

Powder center
Compact device for powder transportation, made of thread with integrated cleaning unit.

Powder circulation
Transport of unapplied powder through reclaim for re-use (comp. to over spray).

Powder clusters
I.e. powder puffs.

Powder dryer
Necessary device for gelling and drying of the powder coating film(see oven types).

Powder film
Desired surface development of the gelled powder coating.

Powder hose
Comp. To transport hose.

Powder puffs
Agglomeration of powder coat on the coated surface.

Powder transport Device
For transport of powder coating from storage container to gun.

Pressure points
Visible notches in the powder coat surface, caused by too much pressure strain, especially at high film build.

Pretreatment
Cleaning and conversion layer development with liquid chemicals (dipping, spraying).

Reclaim
Device to reclaim over spray.

Release agent 1
Sprays used in the metal fabrication industry, to reduce the adhesion of welding residues.

Release agent II
Liquid used for castings, to reduce the adhesion between cast part and casting mold.

Remnant powder 1
Contaminated powder from reclaim.

Remnant powder II
Economically not usable powder coating in carton or warehouse.

Retracted areas
Areas unreachable with powder (i.e. faraday cage), example: form tubing, welded parts.

Return point
Up and down end points in automatic reciprocating powder coating equipment.

Rinse
Removal of pretreatment residues via fresh or de-ionized water.

Run
Running of the powder coating film from the work piece (synonymous with liquid paint) Rust
During corrosion of iron or steel.

Salt residues
Unremoved residues after pretreatment.

Scratch resistance
Durability of the powder coating surface (i.e. abrasion resistance).

Screen tear
Defective screen used to qualify powder, oversize particles may cause flow problems.

Screening analysis
Determination of particle size.

Screening equipment
Integrated in reclaim system to strain powder. External straining possible (min. mesh size approx. 200 [µm] / 8 [mils]).

Scuff resistance
Powder film resistance against abrasive media, i.e. sand, scouring liquid, cardboard, wood, paper.

Security standards
Security standards published by equipment manufacturers and OSHA must be observed.

Shavings
Fine manufacturing contaminations (metal, wood or plastic).

Short circuit
Uncontrolled (electric) contact between high voltage and ground.

Sintering
Depositing of powder in the powder feed system, application equipment or reclaim system.

Snowboard effect
Powder does not adhere to work piece, slides off in sheets, drizzles off.

Softener
Additive used in plastics production.

Softening
Softening of the powder coat film through use of solvents.

Spikes
Elevations.

Spray wash system
Pretreatment of work piece via spray washer(approx. 1.5 bar) mechanical cleaning power.

Spraying
Application of powder coat to part with spray equipment.

Stability
Continuous resistance depending on requirement, for example against chemicals, weather or UV influence.

Substrate
Work piece, to be coated material (steel, aluminum, stainless steel, glass, plastics, MDF).

Super fines
Spectrum of particle size distribution of the powder coating ( 10 [µm]).

Surface defects
Damages to the surface properties of the powder coating.

Sweeping
Light blasting of parts. Mechanical removal of corrosion layer, especially for hot dipped galvanized parts.

Tears
Surface defects, tearing/breaking during insufficient gelling, after mechanical strain.

Temperature curve

Elevating and dropping of substrate temperature during the curing process.

Textures
Surface developments.

TGIC
Triglycidylisocyanurate - Popular hardening system for polyester.

TGIC-Free
Alternative hardener.

Thermoplastics
Re-formable plastics that can be reshaped with re-heating.

Thermosetting coatings
Irreversibly fused film, not changeable by re-heating.

Transport hose
Hose used to transport powder and air mixture from powder container to gun.

Transportation air
Necessary air to transport air to the powder gun. Increasing of air = increased powder consumption.

Tribo charging
Through charging separation (PTFE –rod) powder particles are positively charged and transported to the part.

Use of adhesives
Large selection, check suitability before use.

Voltage
Necessary electrical voltage for charging.

Wall thickness
Material thickness of the work piece.

Welding points
Surface treatment. May be visible through powder coat. Problems with carbon.

Work piece
See substrate.

Wrapping
Accumulation of powder on the backside and/or edge of a work piece.

Yellowing
Color change caused by excessive temperatures or time in direct fired gas ovens.

Zinc coating
Application of a corrosion protection layer (Zn) on steel (galvanizing).

Reference: TIGER Drylac Powder Coatings, TIGER Drylac U.S.A., Inc., 2012.