A coating is a covering that is applied to the surface of an object, usually referred to as the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached **Substrate (locomotion), the surface over which an organism loco ...

. The purpose of applying the coating may be decorative, functional, or both.

Paint Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned wi ...

Paint

s and

lacquer Lacquer is a type of hard and potentially shiny coating A coating is a covering that is applied to the surface of an object, usually referred to as the substrate Substrate may refer to: Physical layers *Substrate (biology), the natural e ...

lacquer

s are coatings that mostly have dual uses of protecting the substrate and being decorative, although some artists paints are only for decoration, and the paint on large industrial pipes is for preventing corrosion and identification e.g. blue for process water, red for fire-fighting control etc. Functional coatings may be applied to change the surface properties of the substrate, such as

adhesion Adhesion is the tendency of dissimilar particles In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physic ...

wettability

corrosion resistance Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide An oxide () is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecu ...

, or wear resistance. In other cases, e.g.

semiconductor device fabrication Semiconductor device fabrication is the process used to manufacture semiconductor devices A semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a El ...

(where the substrate is a

wafer A wafer is a crisp, often sweet, very thin, flat, light and dry cookie A cookie is a baked Baking is a method of preparing food that uses dry heat, typically in an oven, but can also be done in hot ashes, or on hot stones. The most comm ...

), the coating adds a completely new property, such as a magnetic response or electrical conductivity, and forms an essential part of the finished product. A major consideration for most coating processes is that the coating is to be applied at a controlled thickness, and a number of different processes are in use to achieve this control, ranging from a simple brush for painting a wall, to some very expensive machinery applying coatings in the electronics industry. A further consideration for 'non-all-over' coatings is that control is needed as to where the coating is to be applied. A number of these non-all-over coating processes are

printing Printing is a process for mass reproducing text and images An Synthetic aperture radar, SAR radar imaging, radar image acquired by the SIR-C/X-SAR radar on board the Space Shuttle Endeavour shows the Teide volcano. The city of Santa Cru ...

processes. Many industrial coating processes involve the application of a thin film of functional material to a substrate, such as paper,

fabric A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibre Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, ...

fabric

, film, foil, or sheet stock. If the substrate starts and ends the process wound up in a roll, the process may be termed "roll-to-roll" or "web-based" coating. A roll of substrate, when wound through the coating machine, is typically called a web. Coatings may be applied as

liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical objects, ...

liquid

gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas

es or

solid Solid is one of the four fundamental states of matter 4 (four) is a number A number is a mathematical object A mathematical object is an abstract concept arising in mathematics. In the usual language of mathematics, an ''object'' is an ...

solid

Functions of coatings

Adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advantag ...

–

adhesive tape Adhesive tape refers to any one of a variety of combinations of backing materials coated with an adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate ...

, pressure-sensitive labels,

iron-on Iron-on transfers are images that can be imprinted on Textile, fabric. They are frequently used to print onto T-shirts. On one side is paper, and on the other is the image that will be transferred in reverse. The image is printed with iron-on tra ...

fabric * Changing adhesion properties **

Non-stick A non-stick surface is a surface engineered to reduce the ability of other materials to stick to it. Non-stick cookware is a common application, where the non-stick coating allows food to brown without sticking to the pan. Non-stick is often used ...

PTFE Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer A fluoropolymer is a fluorocarbon Fluorocarbons, sometimes referred to as perfluorocarbons or PFCs, are organofluorine B: isoflurane Isoflurane, sold under the brand name Foran ...

PTFE

coated- cooking pans ** Release coatings for example silicone-coated

release liner A release liner is a paper or plastic-based film sheet (usually applied during the manufacturing process) used to prevent a sticky surface from prematurely adhering. It is coated A coating is a covering that is applied to the surface of an object ...

s for many self-adhesive products ** primers encourage subsequent coatings to adhere well (also sometimes have anti-corrosive properties) *

Optical coating An optical coating is one or more thin layers of material deposited on an optical component such as a lens A lens is a transmissive optical Optics is the branch of physics Physics is the natural science that studies matter, its ...

s ** Reflective coatings for

mirror A mirror is an object that reflects an image An image (from la, imago) is an artifact that depicts visual perception Visual perception is the ability to interpret the surrounding environment Environment most often refers t ...

mirror

s **

Anti-reflective coating An antireflective or anti-reflection (AR) coating is a type of optical coating An optical coating is one or more thin layers of material deposited on an optical component such as a lens A lens is a transmissive optical device that focus ...

s example on spectacles ** UV- absorbent coatings for protection of eyes or increasing the life of the substrate ** Tinted as used in some coloured lighting, tinted glazing, or

sunglass Sunglasses or sun glasses (informally called shades or sunnies; more names below Below may refer to: *Earth *Ground (disambiguation) *Soil *Floor *Bottom (disambiguation) *Less than *Temperatures below freezing *Hell or underworld People wit ...

es * Catalytic e.g. some

self-cleaning glass Self-cleaning glass is a specific type of glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, table ...

* Light-sensitive as previously used to make

photographic film Photographic film is a strip or sheet of transparent film baseA film base is a transparent substrate which acts as a support medium for the photosensitive emulsion An emulsion is a mixture of two or more liquids that are normally Miscibil ...

* Protective coatings ** Most surface coatings or

paint Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned wi ...

paint

s are to some extent protecting the substrate e.g. *** Sealing and waterproofing wood *** Sealing the surface of concrete **** Film-forming sealers and floor paint ****

Seamless polymer/resin flooring

**** Bund wall/containment lining ***

Waterproofing Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...

and

damp proofing Damp proofing or a Damp-Proof in construction Construction is a general term meaning the art and science to form Physical object, objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second ...

of concrete walls *** Roof coating *** Concrete

bridge deck A deck is the surface of a bridge A bridge is a structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements ...

membranes *** Sealing and waterproofing of

masonry Masonry is the building of structures from individual units, which are often laid in and bound together by mortar Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps betwe ...

masonry

*** Preserving machinery, equipment and structures **** Maintenance coatings/paints for metals, alloys and concrete **** Chemical resistant coatings ****

UV coating A UV coating (or more generally a radiation cured coating) is a surface treatment which either is cured A cure is a completely effective treatment for a disease. Cure, or similar, may also refer to: Places * Cure (river), a river in France * C ...

***

Wear resistance Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion In earth science, erosion is the action of surface processes (such as Surface runoff, water flow or wind) tha ...

**** Anti-Friction, Wear and Scuffing Resistance Coatings for Rolling-element bearings **** Hard

anti-scratch coating An anti-scratch or scratch-resistant coating is a film or coating that can be applied to optical surfaces, such as the faces of a lens or photographic film, intended to mitigate scratch effects. Usage Anti-scratch coating does not interfere with ...

plastics Plastics are a wide range of syntheticA synthetic is an artificial material produced by organic chemistry, organic chemical synthesis. Synthetic may also refer to: In the sense of both "combination" and "artificial" * Synthetic chemical or s ...

and other materials e.g. of

titanium nitride Titanium nitride (TiN; sometimes known as Tinite) is an extremely hard ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant Corrosion is a Erosion, natural process that converts a refined metal i ...

to reduce scratching and abrasion loss **** Barrier coatings on concrete, metals and alloys subject to erosion/abrasive attack **

Anti-corrosionA corrosion inhibitor is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together b ...

,- ensure metal components have the longest possible lifespan by preventing substrates from external environmental parameters *** Underbody sealant for cars *** Many

plating Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve ...

plating

products *** Preserving equipment and structural steel from degradation *** Under thermal insulation and under protective fireproofing for structural steel *** Adding glass flakes and zinc flakes to improve resistant of water and chemicals permeating ** Passive

fire protection Fire protection is the study and practice of mitigating the unwanted effects of potentially destructive fires. It involves the study of the behaviour, compartmentalisation, suppression and investigation of fire BBQ. Fire is the rapid oxid ...

** Insulation **

Waterproof fabric Waterproof fabrics are fabrics that are, inherently, or have been treated to become, resistant to penetration by water and wetting. The term "waterproof" refers to conformance to a governing specification A specification often refers to a set of ...

and waterproof paper ** Anti-graffiti ** Antimicrobial surface ** Foul release,

anti-fouling Biofouling or biological fouling is the accumulation of microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any ...

and

Biomimetic antifouling coatingBiomimetic antifouling coatings are special coatings that prevent the accumulation of marine organisms on a surface. Typical antifouling coatings are not Biomimicry, biomimetic but are based on synthetic chemical compounds that can have deleterious ...

* Magnetic properties such as for magnetic media like

cassette tape The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape Magnetic tape is a medium for , made of a thin, magnetizable coating ...

floppy disk A floppy disk or floppy diskette (sometimes casually referred to as a floppy or diskette) is a type of disk storage Disk storage (also sometimes called drive storage) is a general category of storage mechanisms where data is recorded by vario ...

s, and some mass transit tickets * Electrical or electronic properties ** Conformal Antenna, e.g., metal coatings on plastic airframes ** Conductive coatings e.g. to manufacture some types of

resistor A resistor is a passive Passive may refer to: * Passive voice, a grammatical voice common in many languages, see also Pseudopassive (disambiguation), Pseudopassive * Passive language, a language from which an interpreter works * Passivity (b ...

s ** Insulating coatings e.g. on

magnet wire Magnet wire or enameled wire is a copper Copper is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consi ...

s used in transformers * Scent properties such as scratch and sniff stickers and labels * Decorative- often to impart a specific colour, but also to create a particular reflective property such as gloss or matt.

Coating Analysis

Numerous methods exist for evaluating coatings, including both destructive and non-destructive methods. The most common destructive method is microscopy of a mounted cross-section of the coating and substrate. The most common non-destructive techniques include ultrasonic thickness measurement, XRF (

X-ray fluorescence X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation In physics Physics is th ...

) coatings thickness measurement, and ultra-micro hardness testing.

Coating formulation

The formulation of the coating depends primarily on the function of the coating and also on aesthetics required such as color and gloss. The four primary ingredients are the

resin In polymer chemistry Polymer chemistry is a sub-discipline of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, stru ...

resin

(or binder),

solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent

which maybe

water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water

(or solventless),

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compound , CH4; is among the simplest organic compou ...

(s) and additives.

Coating processes

Coating processes may be classified as follows:

Vapor deposition

Chemical vapor deposition

Metalorganic vapour phase epitaxy Metalorganic vapour-phase epitaxy (MOVPE), also known as organometallic Organometallic chemistry is the study of organometallic compounds, chemical compound A chemical compound is a chemical substance A chemical substance is a form of m ...

* Electrostatic spray assisted vapour deposition (ESAVD) * Sherardizing * Some forms of

Epitaxy Epitaxy refers to a type of crystal growth or material deposition in which new crystal A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nea ...

Molecular beam epitaxy Molecular-beam epitaxy (MBE) is an epitaxy Epitaxy refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. Th ...

Physical vapor deposition

Cathodic arc depositionCathodic arc deposition or Arc-PVD is a physical vapor deposition technique in which an electric arc is used to vaporize material from a cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. T ...

Electron beam physical vapor deposition Electron-beam physical vapor deposition, or EBPVD, is a form of physical vapor deposition Physical vapor deposition (PVD), sometimes (especially in single-crystal A single-crystal, or monocrystalline, solid Solid is one of the four ...

(EBPVD) *

Ion plating Ion plating (IP) is a physical vapor deposition File:PVD process.svg, PVD process flow diagram Physical vapor deposition (PVD), sometimes (especially in single crystal, single-crystal growth contexts) called physical vapor transport (PVT), ...

Ion beam assisted deposition Ion beam assisted deposition or IBAD or IAD (not to be confused with ion beam induced deposition, IBID) is a materials engineering technique which combines ion implantation with simultaneous sputter deposition, sputtering or another physical vapor ...

(IBAD) *

Magnetron sputtering Sputter deposition is a physical vapor deposition Physical vapor deposition (PVD), sometimes (especially in single-crystal A single-crystal, or monocrystalline, solid Solid is one of the four fundamental states of matter (the othe ...

* Pulsed laser deposition *

Sputter deposition Sputter deposition is a physical vapor deposition Physical vapor deposition (PVD), sometimes (especially in single-crystal A single-crystal, or monocrystalline, solid Solid is one of the four fundamental states of matter (the othe ...

Vacuum deposition Vacuum deposition is a group of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes operate at pressures well below atmospheric pressure Atmospheric pressure, also known as baro ...

Vacuum evaporation Vacuum evaporation is the process of causing the pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''ph� ...

evaporation (deposition) Evaporation is a common method of thin-film deposition. The source material is evaporated in a vacuum A vacuum is space devoid of matter In classical physics and general chemistry, matter is any substance that has mass and takes up spa ...

* Pulsed electron deposition (PED)

Chemical and electrochemical techniques

Conversion coating A Conversion coating is a chemistry, chemical or electrochemistry, electro-chemical treatment applied to manufactured parts that superficially converts the material into a thin adhering coating of an insoluble compound. These coatings are commonly ...

** Autophoretic, the registered trade name of a proprietary series of autodepositing coatings specifically for ferrous metal substrates ** Anodising **

Chromate conversion coating Chromate conversion coating or alodine coating is a type of conversion coating A Conversion coating is a chemistry, chemical or electrochemistry, electro-chemical treatment applied to manufactured parts that superficially converts the material i ...

Plasma electrolytic oxidation Plasma electrolytic oxidation (PEO), also known as electrolytic plasma oxidation (EPO) or microarc oxidation (MAO), is an electrochemical Electrochemistry is the branch of physical chemistry Physical chemistry is the study of macroscopic The ...

** Phosphate (coating) *

Ion beam mixing Ion beam mixing is the atomic intermixing and alloying that can occur at the interface separating two different materials during ion irradiation. It is applied as a process for adhering two multilayers, especially a substrate Substrate may refer t ...

* Pickled and oiled, a type of plate

steel Steel is an alloy An alloy is an admixture of metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appe ...

steel

coating *

Plating Plating is a surface covering in which a metal is deposited on a conductive surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve ...

Plating

Electroless plating Electroless plating, also known as chemical plating or autocatalytic plating, is a class of industrial chemical processes that create metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material ...

Electroplating Electroplating is a general name for processes that produce a metal A metal (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Repu ...

Spraying

Spray painting Spray painting is a painting Painting is the practice of applying paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is ...

* High velocity oxygen fuel (HVOF) *

Plasma spraying Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame). Thermal sprayin ...

Thermal spray Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame). Thermal sprayin ...

ing * Kinetic metallization (KM) * Plasma transferred wire arc thermal spraying * The common forms of

Powder coating Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat or ...

Roll-to-roll coating processes

Common

roll-to-roll In the field of electronic devices, roll-to-roll processing, also known as web processing, reel-to-reel processing or R2R, is the process of creating electronic devices on a roll of flexible plastic, metal foil, or flexible glass. In other fields ...

coating processes include: *

Air knife An air knife is a tool used to blow off liquid or debris from products as they travel on conveyors. Air knives are normally used in manufacturing or as the first step in a recursive recycling process to separate lighter or smaller particles from o ...

coating *

Anilox In printing Printing is a process for mass reproducing text and images An Synthetic aperture radar, SAR radar imaging, radar image acquired by the SIR-C/X-SAR radar on board the Space Shuttle Endeavour shows the Teide volcano. The cit ...

coater *

Flexo Flexography (often abbreviated to flexo) is a form of printing Printing is a process for mass reproducing text and images An Synthetic aperture radar, SAR radar imaging, radar image acquired by the SIR-C/X-SAR radar on board the S ...

Flexo

coater * Gap Coating ** Knife-over-roll coating *

Gravure Rotogravure (or gravure for short) is a type of intaglio Intaglio, the process of cutting a design into a surface, may refer to: * Intaglio, a type of engraved gem or metal signet ring * Intaglio (printmaking), a group of printmaking technique ...

Gravure

coating * Hot melt coating- when the necessary coating viscosity is achieved by temperature rather than solution of the polymers etc. This method commonly implies slot-die coating above room temperature, but it also is possible to have hot-melt roller coating; hot-melt metering-rod coating, etc. * Immersion

dip coating image:Dip coating.svg, A schematic of the continuous dip coating process. Roll of coarse cloth Cloth Bath Liquid material Rollers Oven Scrapers Excess liquid falls back A coating remains on the fabric cloth. Dip coating is an industrial ...

* Kiss coating * Metering rod (Meyer bar) coating * Roller coating ** Forward roller coating ** Reverse roll coating * Screen-printing, Silk Screen coater ** Rotary screen *Slot-die coating, Slot Die coating - Slot die coating was originally developed in the 1950s. Slot die coating has a low operational cost and is easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste. Slot die coating technology is used to deposit a variety of liquid chemistries onto substrates of various materials such as glass, metal, and polymers by precisely metering the process fluid and dispensing it at a controlled rate while the coating die is precisely moved relative to the substrate. The complex inner geometry of conventional slot dies require machining or can be accomplished with 3-D printing. *Extrusion coating - generally high pressure, often high temperature, and with the web travelling much faster than the speed of the extruded polymer **Curtain coating- low viscosity, with the slot vertically above the web and a gap between slotdie and web. ** Slide coating- bead coating with an angled slide between the slotdie and the bead. Commonly used for multilayer coating in the photographic industry. ** Slot die bead coating- typically with the web backed by a roller and a very small gap between slotdie and web. ** Tensioned-web slotdie coating- with no backing for the web. * Inkjet printing * Lithography * Flexography

Physical coating processes

* Langmuir–Blodgett film, Langmuir-Blodgett * Spin coating * Dip coating

References

* ''Titanium and titanium alloys'', edited by C. Leyens and M. Peters, Wiley-VCH, , table 6.2: ''overview of several coating systems and fabriction processes for titanium alloys and titanium aluminides'' (amended) * Coating Materials for Electronic Applications: Polymers, Processes, Reliability, Testing by James J. Licari; William Andrew Publishing, Elsevier, * High-Performance Organic Coatings, ed. AS Khanna, Elsevier BV, 2015, {{Authority control Coatings, Corrosion Materials science Printing