Specifications

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6720649497 SM HP270-1 2012/09 en
6. Maintenance and preventive actions
6.1 Corrosion
Corrosion is the term for a chemical or electrochemical reaction between a material, usually a metal, and its
environment, which produces a deterioration of the material and its properties.
A metal can be exposed to many different kinds of corrosion and below we can see some examples of the ones
applicable to this type of brazed plate heat exchangers.
Pitting and crevice corrosion
They are quite the same, or at least the phenomenon is more or less the same. Pitting may appear on exposed
surfaces, for example attacking the stainless steel if the layer is damaged (this natural layer can be formed when
steel is in contact with air). This kind of defect may cause leakages. Crevices may occur in welds that fail to
penetrate, in flange joints and under deposits on the steel surface.
General corrosion
This is a kind of deterioration, distributed more or less uniformly over a surface. This type of corrosion is more
predictable than pitting.
a) General copper corrosion b) Pitting corrosion in stainless steel
Pict.46 – Examples of corrosion
Unfavourable environment, may lead to the increase of the risk of corrosion and picture 45 shows examples of
corrosion in either stainless steel or copper brazing.
This kind of heat exchangers are sensitive to high concentrations of chloride ions in an oxidizing environment,
because chlorides form a galvanic cell with oxygen and specially stainless steel is too sensitive to this kind of
attack, as well as higher temperatures make chlorides more aggressive.
6.2 Water quality
In order to prevent this kind of phenomena, it’s very important for the installer/technician, to evaluate the water
quality and, warn the end user and prepare the installation accordingly.