Hot Water System Corrosion

Visual inspection and the results of metal ion content in water samples, shows internal pipe corrosion in various locations in the hot water distribution system that compromises the quality of hot water. The cause of the internal pipe corrosion can be attributed to the following factors or a combination of the factors. 

Galvanic Cell Formation. When dissimilar metals are in contact and with the presence of electrolyte, a so-called galvanic cell will be established due to the electrochemical potential difference.2 The result of the galvanic cell is corrosion of the metal that is less noble. For instance, when copper is in contact with iron in the presence of electrolyte 

It should be noted that there is a reduction of pH in the anode area, which further accelerates the iron dissolution (corrosion). 

Temperature Difference. The severe corrosion that takes place in the heat exchange and heat circulation pump locations is explained by the temperature effect. Thermodynamically, a potential difference can result in a temperature difference, even within the same 

Large Cathode and Small Anode. Such a situation is known to lead to an acceleration of corrosion of the anode. If a small section of iron or steel pipe is in contact with a large piece of copper pipe, the area effect will accelerate the corrosion of the iron pipe that acts as an anode of a galvanic cell. 

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Hot Water System Corrosion A schematic diagram of the domestic hot water system is given in Figure 5.22. Visual inspection led to the following observations ... 

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