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Corrosion Glossary - U

  • U-bend specimen: horseshoe-shaped test piece used to detect the susceptibility of a material to stress corrosion cracking.
  • Ultimate strength: the maximum stress a material can sustain without fracture, determined by dividing maximum load by the original cross-sectional area of the specimen.
  • Ultrasonic: an NDE technique which relies on an ultrasonic beam passing through a coating and substrate and providing a signal from the back wall which is then detected. The height of this backwall echo depends on the discontinuity in impedance from the sprayed coating to the substrate. Bonding flaws can be easily seen by the weakening of the back wall echo.
  • Undercutting: a step in the sequence of surface preparation involving the removal of substrate material. Undercutting corrosion of a scribed surface during a testing program is also an indication of poor paint performance.
  • Unfired pressure vessel: a vessel designed to withstand internal pressure, neither subjected to heat from products of combustion nor an integral part of a fired pressure vessel system.
  • Uniform corrosion: corrosion that proceeds at about the same rate over a metal surface.
  • Urethane: an important resin in the coatings industry. A true urethane coating is a two-component product that cures when an isocyanate (the catalyst) prompts a chemical reaction that unites the components.
  • Utility: company that provides a public service or product such as electricity, water, or telephone.
  • UV stabilizers: chemicals added to paint to absorb the ultraviolet radiation present in sunlight.

Link to glossary of corrosion and materials maintenance terms