Processes for Applying Coatings 140

air spray gun

A type of spray gun that uses compressed air at high pressures to apply a coating. Air spray guns use very high pressures, so the efficiency of the process is low.

air-assisted airless spray gun

A type of spray gun that uses compressed air along with hydraulic pressure to spray the coating. Air-assisted airless spray guns speed the process of atomizing liquid into a mist, which speeds the application process.

airless spray gun

A type of spray gun that forces the coating through a tiny hole with hydraulic pressure. The hydraulic pump in these guns drastically increases speed and pressure when spraying a coating.

anode

A positive electrode. Anodic electrocoating systems deposit a negatively charged coating onto a positively charged surface.

anodic electrocoating

Type of electrocoating process in which the surface serves as the anode and the coating material as the cathode. Anodic electrocoating systems deposit a negatively charged coating onto a positively charged surface.

application

The process of spreading a coating onto a surface. Application follows surface preparation.

autodeposition

Electroless coating. A coating process during which a part is immersed in a coating solution, which in turn becomes attracted and adheres to the part surfaces through oxidation reduction.

barrel coating

Also called tumble coating, a method that involves placing a large batch of parts inside a rolling hopper that contains coating material. After the parts are tumbled, the hopper opens to allow the part surfaces to dry.

cathode

A negative electrode. Cathodic electrocoating systems deposit a positively charged coating onto a negatively charged surface.

cathodic electrocoating

Type of electrocoating process during which the coating material serves as the anode, and the surface as the cathode. Cathodic electrocoating systems deposit a positively charged coating onto a negatively charged surface.

circuit

The controlled path for electricity. Voltage is the electrical force that causes current to flow into a circuit.

coil coating system

An automated coating system that uses mechanical rollers to apply coatings.

conductive

Able to act as a path for the movement of electricity. A part must be sufficiently conductive for electrocoating to be a viable coating method.

current

The flow of electricity into a circuit. An electromechanical cell generates current.

curtain coating

An automated method of applying liquid industrial coatings to planar surfaces. During the curtain coating process, a horizontally flat surface passes on a conveyor underneath a steady stream of coating material.

deionized water

A form of purified water that has mineral ions removed. An electrocoat bath usually consists of 90% deionized water and 10% coating material.

dip coating

An application method that involves immersing and then removing a part or part surface at a steady rate from a container holding coating material.

dip-spin coating

An application method that involves placing a large batch of parts into a wire basket and immersing them into a large reservoir of coating material.

electrochemical cell

A device that facilitates chemical reactions by the introduction of electrical energy throughvoltage and current. Electrocoating requires an electrochemical cell to properly function.

electrocoat bath

The conductive coating material into which the coating surface is immersed during electrocoating.

electrocoating

A sophisticated form of dip coating that involves immersing a conductive part into a conductive waterborne coating solution. Electrocoating is also called electrodeposition coating and electrophoretic coating.

electrode

A device within a circuit that conducts electricity. An electromechanical cell contains a positive and negative electrode.

electrodeposition coating

A sophisticated form of dip coating that involves immersing a conductive part into a conductive waterborne coating solution. Electrodeposition coating is also called electrocoating and electrophoretic coating.

electroless coating

Autodeposition. A coating process during which a part is immersed in a coating solution, which in turn becomes attracted and adheres to the part surfaces through oxidation reduction.

electrophoretic coating

A sophisticated form of dip coating that involves immersing a conductive part into a conductive waterborne coating solution. Electrophoretic coating is also called electrodeposition coating and electrocoating.

electrostatic field

An area around the electrical charge that exhibits strong, magnet-like force.

electrostatic fluidized bed

An application process that involves suspending powder particles in an electrically charged air stream. The electrically charged air stream charges the powder particles, which then stick to the part as it enters the container.

electrostatic spraying

An application process that involves a spray gun that adds an electrical charge to powder particles while the part to be coated is grounded.

EPA

Environmental Protection Agency. The governmental agency responsible for administrating laws to control and reduce pollution of air, water, and land systems.

feed rate

The rate at which the coating substrate is passed underneath the coating material during automated coating operations. During the curtain coating process, the feed rate helps to determine the amount and thickness of the coating.

flame spraying

A thermoplastic coating application method that uses a propane flame to propel the coating powder out of a spray gun.

flow coating

An automated method of applying industrial liquid coatings that involves directing numerous individual streams of coating over one or multiple parts that move horizontally on a conveyor. Flow coating can be used to cover multi-dimensional surfaces of a variety of shapes.

fluidized bed

An application process that involves suspending powder particles in an air stream inside a container. The part is preheated and placed in the container, where the powder melts onto the part.

grounded

Connected to an electrically neutral body that can absorb an electrical force. Electrostatic spraying involves using a spray gun to apply an electrical charge to powder particles while the part being coated is grounded.

high volume low pressure gun

A type of spray gun that uses reduced air pressure to spray large amounts of coating. This reduced pressure reduces spray speed, which enables greater control when spraying higher volumes of coating.

hopper

A large, funnel-shaped device. A hopper is used to hold a large batch of parts during the tumble coating process.

hydraulic pressure

Force exerted by liquid under pressure. Hydraulic pressure forces coating material through a tiny hole in an airless spray gun.

ion

A charged molecule. When a metal part is immersed in a coating solution during autodeposition, acids etch the surfaces of the metal part, which releases ions.

manual roller

A hand-held instrument consisting of a foam or fiber cylindrical device and a handle.

manual rolling

A process that involves using a hand-held instrument consisting of a foam or fiber cylindrical device and a handle to apply a coating.

mechanical roller

A device typically made of a pick-up roll and transfer roll used in a coil coating system. Mechanical rollers are often implemented into an automated coating system.

mechanical rolling

A process of using a device typically made of a pick-up roll and transfer roll used in a coil coating system to apply a coating.

phosphating

The process of converting a steel surface to iron phosphate. Preparing a surface for electrocoating often involves phosphating the metal surface.

pick-up roll

A rotating roll with a hardened surface that takes prepared coating material from its storage tray and transfers it to the transfer roll.

planar

Having the character of a flat surface. Manual rollers are often used to apply coatings to planar surfaces.

polarity

In electricity, having two oppositely charged poles, one positive and one negative. During electrocoating, the difference in polarity between the part and the coating causes the coating to adhere.

post-rinse

The step in the electrocoating process that involves submerging the part in a bath after the coating has been applied. Post-rinse is performed to remove the excess coating material.

pouring head

A device that contains a storage reservoir with a slit from which coating material exits. A pouring head is part of a curtain coating system.

preparation

The process of ridding a surface substrate of any contaminants, making it more susceptible to coating adhesion.

redox

Reduction oxidation. A chemical reaction in which electrons are transferred from one compound to another, causing one compound to lose electrons and the other to gain electrons. Electroless coating works by this process.

reduction oxidation

Redox. A chemical reaction in which electrons are transferred from one compound to another, causing one compound to lose electrons and the other to gain electrons. Electroless coating works by this process.

resin

The mixture of ingredients that form the film that covers the surface of an object. Powder coating methods are determined based on the resin of the coating.

solvent

Also known as a carrier. The substance that enables application by lowering a coating's viscosity. Whether a carrier is used depends on the technology used to apply the coating.

spray gun

A device that diffuses coating material through the air and onto a surface.

spraying

A coating application method that involves separating a liquid into fine particles to form a mist that is directed at the surface. Spraying is usually done using a spray gun.

substrate

Also called a surface, the material onto which a coating is applied. A substrate must be prepared prior to the application of a coating.

substrate immersion

A method of coating a surface that involves submerging the surface completely in the coating. Traditional substrate immersion processes include dip coating, dip-spin coating, and tumble coating.

sump

A low-lying resevoir. During flow coating, excess coating material falls off part surfaces and into a sump.

surface preparation

The process of preparing a surface for a coating application. A surface must first be cleaned and protected in order for successful coating performance.

thermoplastic

A plastic that may be heated, shaped, and cooled without damage.

thermoset

A type of plastic that requires heat to cure and is permanently hardened by cooling.

transfer roll

A rubber-coated rotating roll that receives the coating material from the pick-up roll and applies the coating directly to the part surface. Transfer rolls that turn in the same direction as the conveyor are usually used to apply smooth coatings, while an opposite rotation is often used to apply very thick coatings.

tumble coating

Also called barrel coating, a method that involves placing a large batch of parts inside a rolling hopper that contains coating material. After the parts are tumbled, the hopper opens to allow the part surfaces to dry.

venturi

A stream of compressed air. Traditionally, coatings were sprayed by introducing the liquid to a venturi.

viscosity

A fluid's resistance to flow. Carriers reduce the viscosity of a coating enough that the coating can be easily applied to a surface.

VOC

Volatile organic compound. A harmful gas or vapor released into the atmosphere when a liquid solvent volatilizes, or vaporizes. Electrocoating significantly reduces the release of VOCs.

volatile organic compound

VOC. A harmful gas or vapor released into the atmosphere when a liquid solvent volatilizes, or vaporizes. Electrocoating significantly reduces the release of volatile organic compounds.

voltage

Electrical force or pressure that causes current to flow into a circuit. An electromechanical cell generates voltage.

waterborne coating

A coating solution that uses water as part of the solvent. Waterborne coatings are used for electrocoating processes.

wetting

The behavior of a liquid when the liquid contacts a solid surface. Coating with a brush improves a coating's wetting ability.