Corrosion Terminology - T's

tackcoat—athin wet coat applied to the surface that is allowed to dry just until it istacky before application of a thicker wet coat. (Use of a tack coat allowsapplication of thicker coats without sags or runs.)

Tafelplot—aplot of the relationship between the change in potential (E) and the logarithmof the current density (log i) of an electrode when it is polarized in the anodicor cathodic direction, or both, from its open-circuit potential.

Tafelslope—theslope of the nonvertical, nonhorizontal straight-line portion of the E log icurve on a Tafel plot.

tapeadhesion test—a test in which an adhesive tape is applied to a curedcoating, generally after making cuts through the coating to the substrate, andrapidly removed to evaluate the adhesive bond of the coating to the substrate.

tarnish—surfacediscoloration of a metal resulting from formation of a film of corrosion product.

tempering—heat treatmentby heating to a temperature below the lower critical temperature for thepurpose of decreasing the hardness and increasing the toughness of hardenedsteel, hardened cast iron, and sometimes normalized steel.


thermalspraying—ahigh-temperature process by which finely divided metallic or nonmetallicmaterials are deposited in a molten or semimolten condition to form a coatingon a surface when cooled.

thermogalvaniccorrosion—corrosionresulting from an electrochemical cell caused by a thermal gradient.

thermoplastic—a polymericmaterial (typically a resin) capable of being (a) repeatedly softened by heatand hardened by cooling or (b) [not a preferred term, but used for coatings]dissolved by solvent and reformed upon solvent evaporation. [contrast with thermoset]

thermoplastic coating—a coating with a thermoplastic binder.

thermoset—a polymeric material (typically a resin) that undergoes a chemical cross-linking reaction(by mechanisms involving heat, oxidation, catalysis, light [often ultraviolet],electron beam, or chemical additive) leading to a relatively infusible state.[contrast with thermoplastic]

thermoset coating—a coating with a thermoset binder.

throwing power—the relationship between the current density at a point on a surface and its distance from the counter electrode. The greater the ratio of the surface resistivity shown by the electrode reaction to the volume resistivity of the electrolyte, the better is the throwing power of the process.

tidal zone—that portion of a marine structure that is intermittently wetted by tidal action.

top coat—the final coat of a coating system. [also referred to as finishcoat]

touch potential—the potential difference between a metallic structure and a point on the earth’s surface separated by a distance equal to the normal maximum horizontal reach of a human (approximately 1.0 m [3.3 ft]). 

toughness—the ability of a material to absorb energy and deform plastically before fracturing.

transpassive region—the region of an anodic polarization curve, more positive than the passive potential range, in which there is a significant increase in current density(increased metal oxidation) as the potential becomes more positive.

tubercle—a mound ofcorrosion product and deposit capping a region of localized metal loss.

tuberculation—the formation of localized corrosion products scattered over the surface in the form of knob-like mounds called tubercles.