Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers



Last updated: November 16, 2016

What Does Deionization Mean?

Deionization is the process by which both positively charged and negatively charged ions (cations and anions, respectively) are removed from water. These ions are considered contaminants and provide false results in scientific testing, and are also corrosive to metals and metal alloys. Although the name suggests completely ridding water of ions, there are inevitably some that remain.


Corrosionpedia Explains Deionization

Ions are molecules that have differing numbers of protons and electrons. If a molecule has more electrons than protons, it is a negatively charged ion. Likewise, if a molecule has more protons than electrons, it is a positively charged ion. There are three ways to remove these ions from water, effectively deionizing it:

  • Ion exchange: using small plastic cation and anion resin beads to exchange unwanted ions with pure hydrogen and hydroxide molecules to form pure water
  • Separate bed system: using a cation resin in one container to exchange negative ions first, then moving the water to the second container, which has anion resin beads to exchange positive ions
  • Mixed bed system: using both cation and anion resin beads intermixed in the same container to more efficiently attract and exchange the contaminant ions

The applications of deionized water to prevent corrosion are potentially endless and include the following, among others:

  • Wood or metalworking machinery
  • Pipes that transport materials
  • Hulls of ships, particularly Naval warships
  • Automobiles, planes and trains
  • Metal fences

Deionized water is still being tested for its efficiency in reducing corrosion in metal products. The contaminants in non-deionized water are salts in nature which react with the metal to cause rust and rupture. Theoretically, with far fewer of these contaminants, deionized water should be useful in preventing corrosion. Practically, results vary widely depending on a number of variables, and more conclusive testing is needed.

Much work is still needed to conclude the best way to physically apply this deionized water to said items. Perhaps the deionized water needs to be mixed in a different solution to physically seal the metal from the elements, or simply a spray for maintenance applied by the consumer.


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