Ultrasonic Gauge. Instrument for measuring material thickness by the time sound takes to travel through it.
Ultrasonic Thickness Measurement. Determining thickness of a solid substrate, such as steel, through equipment that applies wave energy above the normal hearing range and then times its retroreflection.
Ultraviolet (UV). A band of electromagnetic radiation between 10 and 400 nanometers in wavelength. The part of the UV spectrum in the actinic region (280 to 315 nanometers) is especially destructive to paint films. Ultraviolet energy also sometimes is used to cure a coating. “Black light” is a popular term for UV radiation. [PCG]
Undercutting. The penetration of a coating and the spread of delamination or corrosion from a break or pinhole in the film or from unprotected edges. [PCG]
Upper Explosive Limit (UEL). The concentration at ordinary ambient temperatures of a compound in air above which an explosion will not occur if the mixture is ignited. UEL is expressed as a percent of the gas vapor in air by volume. When concentrations of a substance in air are below the upper explosive limit and above the lower explosive limit (LEL), the mixture will burn and explode. See also Lower Explosive Limit. [PCG]
V
Vacuum Blasting. Abrasive blast cleaning using a vacuum shroud to capture dust, debris, and other materials while they are being generated and prevent them from escaping into the environment. See Abrasive Blast Cleaning. [PCG]
Vehicle. The liquid portion of paint, in which the pigment is dispersed; it is composed of binder and thinner. [CED]
Viscometer. An instrument for measuring flow properties. [CED]
Viscosity. The quality or property of a fluid (i.e., paint) that causes it to resist flow. A high viscosity coating is thick; a low viscosity coating is thin. [PCG]
Viscosity Cup. A laboratory or field instrument for measuring the viscosity of a liquid by timing the liquid’s flow through an opening in the bottom of a small bowl.
Visual Comparator. One of several systems used to visually estimate the profile of an abrasive blasted steel surface. See Surface Profile Comparator.
Volatile. (1) Easily evaporated. (2) Any liquid that evaporates quickly. [PCG] Volatile Organic Compound (VOC). (1) Any organic compound that reacts in the atmosphere with nitrogen oxides in the presence of heat and sunlight to form ozone. (2) Any organic compound (other than those designated by EPA as having negligible photochemical reactivity) that is emitted into the atmosphere during the application or curing of a coating. It is detected by reference methods such as EPA Method 24 or ASTM D 2369. [PCG]
W
Washability. Ease with which the dirt can be removed from a paint surface by washing; also refers to the ability of the coating to withstand washing without removal or
substantial damage. [CED]
Wash Primer. A carefully balanced one- or two-component system containing an inhibiting chromate pigment, phosphoric acid, and a synthetic resin binder mixed in an alcohol. On clean, light alloy or ferrous surfaces, and on many nonferrous surfaces, such primers provide excellent adhesion, partly due to a chemical reaction with the substrate, and a corrosion-inhibiting film that is a good basis for the application of subsequent coats of paint. [CED]
Water Blast Cleaning. A water cleaning method in which abrasive is injected into the water stream.
Waterborne Coatings. Paint, the vehicle of which is a water emulsion, water dispersion, or ingredients that react chemically with water. Also called water-based and water-
reducible coatings.
Water Break. The appearance of a discontinuous film (beads) of water on a surface, signifying nonuniform wetting and usually associated with a surface contamination. [ASTM, CED]
Water Cleaning. A method of using pressurized water, heated or unheated, with or without detergent, to prepare surfaces for coating. Low-pressure water cleaning uses pressures up to about 34 MPa (5,000 psi); high-pressure water cleaning ranges from 34 MPa (5,000 psi) to 170 MPa (25,000 psi); and ultrahigh-pressure water cleaning uses pressures above 170 MPa (25,000 psi). When pressures exceed 69 MPa (10,000 psi), a jet nozzle is used and the process is called waterjetting.
Waterjetting. The use of water at high or ultrahigh pressure to prepare a surface for recoating. High pressure waterjetting is cleaning performed at pressures from 69 to 170 MPa (10,000 to 25,000 psi). Ultrahigh pressure waterjetting is cleaning performed at pressures above 170 MPa (25,000 psi). [SSPC-SP 12/NACE 5].
Water Trap. A structural feature in which liquid (such as rainwater) may accumulate from the environment.
Weathering. Behavior of coating films when exposed to natural weather or accelerated weathering equipment, characterized by changes in color, texture, strength, chemical composition, or other properties. [CED]
Weathering Topcoats. Exterior finishes designed to resist deterioration from ultraviolet light, rain, and other natural destructive elements in the atmosphere.
Weld Spatter. Beads of metal produced during the welding process that adhere to the surface near the weld. [PCG]
Wet Abrasive Blast Cleaning. Surface preparation method using conventional dry abrasive blasting equipment supplemented with modules to inject water into the abrasive stream. Ideally, the water encapsulates the abrasive particles with a thin film of moisture to suppress and contain the dust generated by the impact of the abrasive with the
substrate.
Wet Bulb Depression t – tw. The difference between the dry-bulb temperature and the wet-bulb temperature. [ASTM]
Wet Bulb Temperature, tw. The temperature recorded on a wet bulb thermometer. See also Dry Bulb Temperature and Psychrometer. [PCG]
Wet Bulb Thermometer. The thermometer on a sling or other psychrometer with a bulb covered by a wet cotton sock. See Psychrometer.
Wet Film Thickness (WFT). Thickness of the liquid coating film immediately after application. [CED]
Wet Film Thickness Gauge, Notch Type. Gauge with one or more faces cut in a series of notches that is used to determine coating wet film thickness as described in ASTM D 4414.
Wetting. Ability of a vehicle to spread uniformly and rapidly over the surface of pigment particles. A vehicle with good wetting properties assists in the grinding or dispersion of pigments and the ability to wet the surface to which the finished coating is applied. [CED] (2) The ability of a coating to come into close contact with the surface over which it is applied. [PCG]
Wetting Agent. Material used in a coating to reduce the surface tension of the vehicle or binder in order to assist in grinding or dispersing pigments or to improve the ability of the coating to wet the surface. [PCG]
White Metal Blast Cleaning. Highest grade of blast cleaning. According to SSPC-SP 5/NACE No. 1, a white metal blast cleaned surface is free of all visible oil, grease, dirt, dust, mill scale, rust, paint, oxides, corrosion products, and other foreign matter. [PCG] Wire Brush Cleaning. Cleaning a surface with a hand or power tool wire brush. [PCG] Work Mix. See Abrasive Mix.
Work Permit. Formal instruction, issued daily or weekly, to allow work to take place in a hazardous environment.
Woven Roving. A cloth consisting of glass fibers woven in a pattern to impart strength when used to reinforce a coating or other composite system.
X
Xylene. An aromatic solvent used in the manufacture of paints. It also is used widely as a thinner and cleanup solvent. The flash point of xylene is about 80°F (27°C). [PCG]
Z
Zinc. A hard, metallic element with a bluish tinge. Zinc or its compounds are used as reinforcing and corrosion-resistant pigments. Zinc dust is used in zinc-rich coatings to provide galvanic protection to steel. It is also the basis for galvanizing and sprayed zinc coatings.
Zinc-Rich. High in zinc dust content; a generic type of coating described in SSPC Paint 20.
Zinc-Rich Coating. Anti-corrosive coating for iron and steel. Zinc-rich coatings use zinc dust in a concentration sufficient to provide electrical conductivity in the dried film. This enables the zinc metal to corrode preferentially to the ferrous substrate, giving galvanic protection. [PCG] See also Galvanic Protection.
Bibliography
ACI: Cement and Concrete Terminology. ACI International: Farmington Hills, MI, 2000. ASM Metals Handbook. ASM International: Metals Park, OH, 1987.
ASTM Annual Book of Standards. ASTM: West Conshohocken, PA, 2003.
Bridge Inspector’s Training Manual/90. U.S. Department of Transportation/Federal
Highway Administration: Washington, DC, 1979.
Coatings Encyclopedic Dictionary (CED). Stanley LeSota, ed., Federation of Societies
for Coatings Technology: Blue Bell, PA, 1995.
Dictionary of Architecture and Construction (DAC). C.M. Harris, ed., McGraw-Hill:
New York, 1975.
EPA: Glossary for Air Pollution of Industrial Coatings Operation. U.S. Environmental
Protection Agency: Washington, DC, 1983.
Industrial Lead Paint Removal Handbook (ILPR). Kenneth A. Trimber, ed., SSPC:
Pittsburgh.
IUPAC Glossary of Atmospheric Chemistry Terms. Atmospheric Chemistry Division,
National Center for Atmospheric Research: Boulder, CO, 1990.
MPDA: The Master Painter’s Painting and Decorating Terminology Glossary. Master
Painters & Decorators Association: Burnaby, B.C., 1997.
PDC: Painting and Decorating Craftman’s Manual and Textbook. Painting and
Decorating Contractors of America: Fairfax, VA, 1975.
Appendix C