Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Dielectric Shield

Last updated: March 28, 2019

What Does Dielectric Shield Mean?

A dielectric shield is a material that is electrically nonconductive in nature. It is placed between an anode and cathode in the form of pipe or film to improve current distribution in a cathodic protection (CP) system. This is used to prevent formation of corrosion in the form of electrochemical cells.

Dielectric shield materials include:

  • Epoxy materials
  • Coal-tar epoxy resins
  • Polyurethane coatings
  • Rubber coatings

Corrosionpedia Explains Dielectric Shield

The efficiency of cathodic protection (CP) of steel pipelines can be improved greatly with the use of solid film dielectric shields such as polyethylene tapes. These highly resistive dielectric film materials prevent electric current from reaching the underlying metal. Inner and outer thickness of the dielectric shields ranges from 22 mils to 100 mils.

Air, having a dielectric value of one, is the best dielectric available. However, it is not feasible to build a cable with air as an isolating medium between multiple conductors. By injecting nitrogen into a solid, dielectric values closer to one can be attained.

Materials having dielectric values close to one include:

  • Polyethylene
  • Teflon
  • Polypropylene

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