Coating Faults AA

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Failure Analysis of coating

Transcript of Coating Faults AA


an excerpt from SSPC's Protective Coatings Glossary

AABRASIONThe wearing away of a surface by action such as by rubbing, scraping, erosion, or other frictional process.

ABRASION RESISTANCEThe ability of a coating to resist being worn away and to maintain its original appearance and structure when subjected to rubbing, scraping and wear. [ASTM]

ACCELERATED AGINGAny set of conditions used in an attempt to produce in a short time the results obtained under normal conditions of aging. In accelerated aging tests, the usual factors considered are heat, light, water, and oxygen, either separately or combined. [Painting/Coatings Dictionary]

ADHESION FAILUREA failure between two distinct coating layers or between the substrate and the first layer of coating. See ADHESION TEST, TENSILE (PULL-OFF) in main glossary.

ADULTERATIONThe addition of foreign materials to a manufactured product.

AFTER-TACKFilm defect in which the coated surface, having once reached a tack-free state, subsequently develops a sticky condition. [CED]

AGING(1) Storage of paints, varnishes, etc., under defined conditions of temperature, relative humidity, etc., in suitable containers, or as dry films of these materials for the purpose of subsequent tests [Painting/Coatings Dictionary]; (2) Gradual changing of a coatings chemical and/or physical properties over a period of in-service response time.

AIR BUBBLEDry bubble in coating film caused by entrapped air. [CED]

AIR ENTRAINMENT(1) The process of causing small air bubbles to form in paint or wet paint film; (2) Intentional incorporation of small air bubbles in concrete to improve such physical properties as freezethaw resistance.

AIR ENTRAPMENTInclusion of air bubbles in coating film or other solids such as concrete. [CED] See BUBBLING.

ALLIGATORING(1) A type of crazing or surface cracking of a definite pattern, as indicated by its name. The effect is often caused during weather aging; (2) the cracking of the surface bitumen on a built-up roof, producing a pattern of cracks similar to an alligators hide; the cracks may not extend through the surface bitumen. [CED]; surface cracking of a paint film having the appearance similar to alligator hide. [ASTM]; alligator cracking is the vertical cracking of a coating with a pattern of closed cells or islands of unbroken coating. See also CRACKING.

AMINE BLUSHSurface opalescence (blush) on epoxy films caused by reaction of amine co-reactant with carbon dioxide and water to form an amine carbamate. This can affect adhesion of any subsequent coat if not properly removed.


FAILURE TERMS ANTI-FOAMING AGENTAdditive used to control or prevent foam formation during the manufacture or application of coatings.

ANTI-LIVERING AGENTAdditive used to prevent the livering of a coating. See LIVERING.

ANTI-SAG AGENTAdditive used to control sagging of a coating.

ANTI-SETTLING AGENTSubstance incorporated into a pigmented paint to retard settling and to maintain uniform consistency during storage or painting operations. These additives normally function by altering the rheological properties of the paint.

ANTI-SKINNING AGENTAny material added to a coating to prevent or retard the processes of oxidation or polymerization that result in the formation of an insoluble skin on the surface of the coating in a container. [Painting/Coatings Dictionary]

ANTI-WRINKLING AGENTMaterial added to surface coating compositions to prevent the formation of wrinkles in films during curing.

BBALD SPOTArea or patch, usually in a wrinkle finish film, which has failed to wrinkle or give the desired optical effect. [CED]

BIOCIDEA chemical agent capable of killing organisms such as those responsible for microbiological degradation.

BIODETERIORATIONAny undesirable change in material properties brought about by the activities of microorganisms. [CED]

BIOFOULINGBiological encrustation of surfaces in sea water by flora and fauna, e.g., barnacles. See FOULING.

BIOLOGICAL DEFACEMENTDisfiguring of surfaces by growth of microorganisms.

BLEACHING(1)Bleaching is a uniform loss of color of a paint or varnish. This may be due to internal chemical or physical action in the paint itself, to influences from the surface on which it is applied or to weathering or contamination from the atmosphere; (2) Intentional lightening of the color of a material such as wood, vegetable oils, varnishes, etc. [CED]; removing color. [AM]

BLEEDCoating discoloration by the diffusion of coloring matter from a previously painted or unpainted surface (e.g. asphalt) by the action of the coating solvent.


FAILURE TERMS BLEEDINGThe diffusion of colored matter from a substrate (including a previously applied paint film) into a newly applied finish, resulting in a discoloration of the finish. The solvent carrier of the newly applied finish normally transfers the coloring matter. Examples are bituminous surfaces, wood knots, organic pigments, contaminants.

BLEEDING KNOTUsually circular-shaped discoloration in stained or painted siding. [CED]

BLEED-THROUGHAppearance of color on a newly painted surface by migration of a previously painted substrate beneath it.

BLISTERAn undesirable rounded elevation of the coating resulting from the local loss of adhesion. See also BLISTERING.

BLISTERING(1) Formation of dome-shaped projections (blisters) in paints or varnish films resulting from local loss of adhesion and lifting of the film from an underlying paint film (intercoat blistering) or the base substrate. The standard test method for evaluating the degree of blistering of paints is described in ASTM D 714; (2) The irregular raising of a thin layer at the surface of placed mortar or concrete during or soon after completion of the finishing operation, or in the case of pipe after spinning; also bulging of the finish plaster coat as it separates and draws away from the base coat [ACI]; (3) Formation of blisters in films of paint or varnish. Blistering may be caused by solvent entrapment, moisture diffusion through the coating, or excessive moisture in the substrate.

BLISTERING RESISTANCEA coatings ability to resist the formation of blisters.

BLOCK COATA barrier coat or transition primer/tie coat that prevents incompatible paints from touching. See also BARRIER COAT, TIE COAT in main glossary.

BLOCKING(1) The undesirable sticking together of two painted surfaces when pressed together under normal conditions or under specified conditions of temperature, pressure, and relative humidity; (2) Undesired adhesion between touching layers of material, such as occurs under moderate pressure and sometimes pressure and heat, during storage or fabrication. [CED]

BLOCKING RESISTANCEThe ability of two coated surfaces to resist sticking together during normal handling and storage.

BLOOMINGThe reduction of a coating gloss caused by materials exuding in or from an applied film. Unlike bleeding, the solvent-caused movement of material is from the coating itself and not the substrate.

BODYINGThickening of an oil through thermal processing; (2) An increase in the viscosity or thixotropy of a paint, varnish, or lacquer which occurs during storage. [MPDA]

BOUNCE BACK(1) The rebound of atomized paint particles during spray application. This effect is most pronounced when paint is being applied into corners or boxed areas. The resultant return flow of atomized air carries some of the paint particles away from the surface. See also DRY SPRAY, OVERSPRAY; (2) Rebound of abrasive particles during abrasive blasting.


FAILURE TERMS BRITTLESusceptible and being easily broken, fragile.

BRITTLENESSDegree of susceptibility to cracking or breaking by bending. [AM]

BRONZINGA subjective, descriptive, appearance term applied to metal-like reflectance which sometimes appears at the surface of nonmetallic colored materials. It is perceived at the specular angle, by observing the image of a white light source, for example, and is characterized by a distinct hue of different predominant wavelength than the hue of the paint itself. The origin of the selective specular reflectance is generally considered to be reflectance from very small particle size pigments partially separated from the surrounding vehicle at or near the surface. [CED]

BRUSH MARKS(1) Marks produced in a coating by the bristles of a brush during application. Depending on the leveling characteristics of the paint, brush marks may or may not remain in the dried coating; (2) Small ridges or valleys produced in a paint film by the combing action of the bristle of a brush. [CED]

BUBBLE BUSTERCompound used to control the formation of bubbles in a coating.

BUBBLINGAir bubbles or solvent vapor bubbles found temporarily in the wet film of a coating or permanently in the dry film.

BUG HOLESSmall regular or irregular cavities, usually not exceeding 15 mm in diameter, resulting from entrapment of air bubbles in the surface of formed concrete during placement and compaction.

CCAKINGHard setting of pigment from a liquid paint during storage.

CAN STABILITYResistance to deterioration of liquid paint in original container.

CASE HARDENINGSurface hardening without thorough drying of film.[CED] See SURFACE DRYING, TOP DRYING in main glossary.

CATASTROPHIC COATING FAILUREA coating failure that is sudden, very dramatic, and serious.

CATASTROPHIC CORROSIONMetallic degradation resulting in substantial loss of metal.

CAT EYE(S)Hole or holiday shaped like a cats eye; cratering. [AM] See CRATERING.

CATHODIC DISBONDINGMechanical lifting of a coating caused by hydrogen bubbles formed when cathodic protec