Water hardness and cleaning processes - Pola & Massa - Machines for PCBs surface preparation

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Water hardness and cleaning processes

Water hardness, in common acceptations, means a value able to measure the content of soluble salts, basically calcium and magnesium, and possible existing heavy metals in the water. Hardness salts are usually existing in the water as sulfates, chlorides, nitrates, carbonates or hydrogen carbonates; they are normally soluble but by heating or by evaporation can be precipitated generating lime scale deposits or other.
After this brief introduction, that allows us to well understand how water chemical composition is a primary element that have to be well evaluated in the washing processes, it is crystal clear that we do not have to underestimate this aspect: it can be one of the most important reason for efficiency losses in the washing process. Let’s try to better understand negative underlying reasons behind this aspect.
Calcium and Magnesium presence, in high percentages in the water, could significantly reduce washing process efficiency, especially in case detergents are part of the process, because are making insoluble salts in combination with surfactants. This is what is happening when you try to wash your hands with soap and sea water or what it is happening in the mountains, where usually water has a low quantity of salts, and hands rinsing takes a lot of time. Furthermore, Calcium and Magnesium, can concretely contribute to reinforce existing dirt on the cleaned surfaces and obviously inside the industrial washing machine, especially in the heating and/or cooling coils, dramatically reducing both their efficiency and lifetime, damaging the washing machine. For this reason many ingredients used in making detergents should be focus on minimize or neutralize water hardness, so that other ingredients can properly act during washing process. Even detergent quantity used during washing process should change according water hardness because, when this parameter is high, a quantity of the detergent is rendered ineffective by it and consequently more detergent is necessary.
Ad additional issue is coming up in case washing is followed by an high temperature drying process. Also in such a case water hardness is playing an important role. In order to avoid encrustations and lime scale deposits on pieces treated after drying, highly undesirable for aesthetic and/or functional reasons (i.e. pieces have to be painted and so a perfectly cleaned surface is requested to guarantee a proper adherence during painting process), water hardness have to be restricted to acceptable percentages. Requested water hardness features, if not existing in the water used in the process, can be reached by dedicated centralized filtering systems or using, in addition to the washing machine, a suitable water softener. This softener allows, at least during last phases of the washing process and using water without or with a limited content in salts, to remove above mentioned aspects getting perfectly cleaned pieces.
Water hardness can be measured using different parameters, country by country. Just to give some examples, in Germany water hardness is measured using German degrees (°dH) while in the United States of America water hardness is measured using grains per gallon (gr/gal).

For further details to optimize your washing process do not hesitate to contact Pola e Massa engineers.