Critical Pitting Temperature (CPT)

Definition - What does Critical Pitting Temperature (CPT) mean?

Critical pitting temperature (CPT) refers to the degree of hotness or coldness of an environment that prompts the onset of pitting and/or crevice corrosion in a metallic substrate. Pitting corrosion is a form of localized corrosion that attacks in the form of spots or pits.

Corrosionpedia explains Critical Pitting Temperature (CPT)

The susceptibility of a metal, particularly steels, to undergo pitting corrosion increases with a corresponding increase in temperature. Metal applications in oil & gas and seawater industries are particularly prone to severe localized corrosion like pitting and crevice corrosion.

Critical pitting temperatures (CPTs) are widely determined by the use of the following international standard guidelines:

  • ASTM G48-03
  • ASTM G150-99

Other ways to determine CPT are:

  • The use of electrochemical noise (ECN) testing techniques; however, these may result in a false CPT
  • Cyclic potentiodynamic polarization
  • Potentiostatic techniques
  • High temperature tests in autoclaves simulating production conditions
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