Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers



Last updated: June 7, 2018

What Does Postchlorination Mean?

Postchlorination is the final step in the treatment of water. It is a method of adding a minimum level of chlorine into the water mainstream down to distribution. The purpose of it is to remove pathogenic microorganisms, which can cause a variety of diseases, and also to prevent the growth of harmful microorganisms by maintaining low levels of chlorine in pipelines and home plumbing.


Corrosionpedia Explains Postchlorination

Postchlorination is a treatment process that occurs before water leaves the treatment plant. It is the addition of chlorine to the water in order to prevent microbial growth. Ideally, there should be 0.2 to 0.1 parts of chlorine per million parts of water.

There is also a need to add lime to the treated water prior to its distribution to the water system. As a part of postchlorination, calcium oxide or lime is added to raise the pH of the water. This makes the water less likely to corrode, and therefore less likely to damage metals such as copper, lead and brass.

High levels of these metals in the water can lead to health hazards as well as economic and aesthetic problems. Corrosion is an electrochemical oxidation of metals in reaction to its environment. This event results in:

  • Destruction of metals
  • Leaks
  • Rusty red water
  • Damage to:
    • Pipelines
    • Storage tanks
    • Home plumbing fixtures

In order for water to be potable, it needs to be stable. Stable water means it is not corrosive. Corrosion control is important and included in water treatment for consumers to have safe water. This is done by chemical treatment or physical protection.


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