C

Can coating
Coating of tin cans, lids and tubes or the sheets they are made of. The stove enamel coats are applied one after the other onto tin plate, steel (black plate), or aluminium and baked separately.

Catalyst
Additive used to increase the rate of a chemical reaction. Not chemically consumed in the reaction (different from curing agent).
Syn. Accelerator

Caustic
Strong base or alkaline material.

Cellulosic resin
Resin based on a complex carbohydrate (C₆H₁₀O₅)_n formed of microfibrils of glucose molecules.

Cellulosic thickener
Rheological additive for water-based paints based on cellulosic derivatives.

Centipoise
One hundredth of a poise. Unit of measurement for viscosity. (1.0 centipoise = viscosity of water at room temperature).

Chalking (extended definition)
Coating defect: formation of a powdery surface condition due to the disintegration of the surface binder or elastomer caused by weathering, fuel, or other destructive environmental factors (exposure to ultraviolet radiation...). Results on a loss of gloss.

Checking
Coating defect: cracks in the surface of a paint film.

Chelating agent
Additive that can form several bonds to a metal ion, in order to deactivate them.
Examples of chelating agents are: EDTA, ethylenediamine, phosphite.
Syn. Complexing agent

Chemical resistance
Coating's resistance to solvents, acids, and alkali testing done under watch glass for 24 hours.

Chemisorption
Irreversible adsorption due to the formation of chemical bonds between the molecules of sorbat and sorbent across the interface. Chemisorption is employed in the surface modification of pigments and substrates as more efficient than the physical adsorption.

Chlorinated rubber
Resin formed by the reaction of rubber with chlorine gas. Often used for chemical or water resistant properties.
Syn. Chlorobutadiene, Neoprene, Polychloroprene

Cleaner
Contamination removing material (detergent, alkali, acid...). Usually water borne.

Coagulant
Reagent inducing chemical coagulation capable of destroying dispersions, including pigment preparations and dispersion-type paints.
Some examples of coagulants are: salts, acids and some other electrolytes, polar solvents...
Syn. Coagulating reagent

Coagulation
Irreversible particle aggregation that occurs in pigment suspensions, latexes, emulsions and dispersions. Can be caused by various destabilizing factors such as addition of electrolytes, mechanical shear, heat, freezing/thawing cycles, etc... .

Coalescence
Formation of resinous or polymeric material when water evaporates from an emulsion or a latex

Coalescing agent
Additive which improves particle coalescence. Facilitates the formation of coherent films from latexes and latex paints by temporarily plasticizing (softening) the vehicle system. Coalescing agents reduce Tg value, but evaporate from a drying film during the film forming process.

Coal tar
Dark brown to black bituminous material produced by the destructive distillation of coal.

Coat
Coating applied to a surface in a single application to form a film when dry.

Coating
Liquid, liquifiable or mastic composition that is converted to a solid protective, decorative or functional adherent film after application as a thin layer.

Coating defects
Defects of wet and consequent dry coating films, affecting coating appearance and sometimes performance.
Examples of coating defects: bubbles, craters, pinholes, orange peel, Benard Cells... .

Coating system
Number of coats separately applied, in a predetermined order, at suitable intervals to allow for drying and curing, resulting in a completed job.

Cobwebbing
Premature drying of a coating during spraying causing a spider web effect.

Cohesion
State in which the particles of a paint film are held together into a continuous film by primary or secondary valence forces.

Coil coating
Process by which paint is deposited by a series of rubber rollers which meter a thin film of coating onto a continuous web of metal or plastic. After coating, the sheets are rolled up to form so-called coils.

Colloid (extended definition)
Suspension and dispersion of submicron particles in a liquid medium without their dissolution in the medium.

Colloid stability
Ability of colloids to keep their dispersion, uniformity and associated properties despite the excess of interfacial energy and a possible difference in the density between the disperse phases and medium phase. Loss of colloid stability can result in sedimentation.

Color
Aspect of paint film that depends upon the spectral composition of the incident light, the spectral reflectance or transmittance of the film, and the spectral response of the observer, as well as the illuminating and viewing geometry.

Colorant
Dye, pigment, or other agent used to impart a color to a coating.

Color retention
Ability of a coating to retain its original color during weathering or chemical exposure.

Combination drier
Drier based on a combination of primary driers and secondary driers.

Compatibility
Ability of two or more coating components to mix with each other in a wet or dry state to form a homogeneous composition without specific interactions. Compatibility of the binder with other components (additives, other resins, solvents etc.) is considered a major principle for formulating stable, quality paints.

Compatibilizer
Substance of coating formulations (additive, co-solvent ...) which improves the compatibility between resins.

Conductivity improver
Compound which improves the mobility of electrical charges in the paint.

Conical Mandrel
Instrument used to evaluate a coating's resistance to cracking when bent over a specified radius.

Copolymer
Large molecules obtained by simultaneous polymerization of different monomers, as in vinyl copolymers.

Corrosion
Decay, oxidative decomposition, or deterioration of a metal in contact with its environment.

Corrosion inhibitor
Additive used to protect lubricated metal surfaces against chemical attack by water or other contaminants. Two different types of corrosion inhibitors are available: flash-rust inhibitors and inhibitors for long-term corrosion protection.

Coupling agent
Substance which promotes or establishes a stronger bond at the resin matrix/reinforcement interface.
See also Adhesion promoter
Syn. Compatibilizer

Cracking
Coating defect: splitting of a coating film as a result of aging, formation of internal stresses or deformation of substrates.
See Crazing

Cratering (extended definition)
Coating defect: small, shallow, bowl-shaped depressions in a coating film. These depressions frequently have drops, particles or bands of material at their centers and raised circular edges. Some common causes of cratering are: gel particles, oil droplets from air lines, and substrate contamination.

Crawling
Coating defect: tendency of a wet paint film to recede from certain areas of a painted surface. This substrate de-wetting can be induced by a substrate contamination.

Crazing (extended definition)
Coating defect: formation of surface cracks (similar to cracking) that change the properties of the film. However, it is much less severe and does not penetrate to the underlaying surface.

Creaming
Coating defect: separation of emulsions. Particles of the disperse phase concentrate in the upper layer, forming a cream-like highly concentrated emulsion.

Crosslinking
Formation of chemical bonds between polymer chains leading to the formation of a three dimensional network. This kind of process has the effect of producing gel in a thermoplastic polymer or converting it into a thermoset polymer.

Crosslinking agent
Catalytic or reactive agent which when added to resin causes crosslinking of chains.
Syn. Curing agent, Hardener

Cross spraying
Coating application consisting in spraying the first pass in one direction and the second at a right angle to the first, providing more even film distribution.

Cure
Process by which a coating is converted from the liquid to the solid state by changement of the properties of the resin by chemical reaction. Enamels cure. Lacquers do not cure.
Syn. Crosslinking

Curing agent
Functional component of coating formulation, which reacts with liquid resins during the film forming process to give hard, insoluble films.
Syn. Crosslinking agent

Curtains
Coating defect: long horizontal runs in a coating film that occur on vertical surfaces when a coating is applied too heavily.