Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Non-Carbonate Hardness

Last updated: June 29, 2019

What Does Non-Carbonate Hardness Mean?

Non-carbonate hardness is the part of water total hardness that is not generated by carbonates, but mainly by anions of sulfate.

It is also the measure of magnesium and calcium salts apart from bicarbonate and carbonate salts like magnesium chloride and calcium sulfate. It is one of the components of total hardness along with carbonate hardness.


Corrosionpedia Explains Non-Carbonate Hardness

Non-carbonate hardness is the measure of magnesium and calcium salts aside from bicarbonate and carbonate salts, such as:

  • Calcium sulfate
  • Magnesium chloride

Water turns hard when it comes in contact with divalent, soluble and metallic cations. The two major cations that make the water hard are magnesium and calcium. The total hardness of water is the sum of the non-carbonate and carbonate hardness. The level of both these hardness measurements relies on water’s alkalinity.

Hardness is the ability of water to precipitate soap. Both magnesium and calcium can precipitate soap, which in turn forms curd that results in rings in bathtubs and similar fixtures as well as graying, yellowing or brightness loss in washable fabrics. To fight these issues, synthetic detergents have been manufactured which can tie up water’s hardness ions.

Hard water can form scale, which leads to various problems like water spots when water is left to dry on plumbing fixtures, glassware, metal ware and other materials. Scaling in valves, pumps, water meters and other materials can cause corrosion, especially on movable parts.

Removing the total hardness in water is known as softening. Although this is not a mandatory part of water treatment, hard water, as mentioned, can cause negative consequences. Therefore, industries usually require softer water in their operations and for consumption by the public.


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