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Effect of cooling medium on corrosion of heat exchanger
Mar 17, 2020

Effect of cooling medium on heat exchanger corrosion the most commonly used cooling medium in industry is a variety of natural water. There are many factors affecting the corrosion of metal, the main factors and their effects on several commonly used metals:


1.Dissolved oxygen dissolved oxygen in water is an oxidant that participates in the cathodic process and therefore generally promotes corrosion. When the concentration of oxygen in water is not uniform, the concentration of oxygen battery will be formed, causing local corrosion. For carbon steels, low-alloy steels, copper alloys, and some grades of stainless steel, melting oxygen is the most important factor affecting their corrosion behavior in water.


2. In the absence of oxygen in water, CO2 will cause corrosion of copper and steel, but will not promote corrosion of aluminum. Trace amounts of ammonia corrode copper alloys, but have no effect on aluminum and steel. H2S promotes corrosion in copper and steel, but has no effect on aluminum. SO2 reduces the pH value of the water and increases the corrosivity of the water to the metal.


3.Hardness generally speaking, the higher the hardness of fresh water, the less the corrosion of copper, zinc, lead and steel. Very soft water is very corrosive, in this water, do not use copper, lead, zinc. In contrast, lead is resistant to corrosion in soft water and produces pore erosion in hard water.


4. The corrosion of steel with pH value is small in water with pH of >11, and the corrosion increases when the pH value is less than 7.


5. The influence of ions chloride ions can destroy the surface of passivated metals such as stainless steel and induce pore erosion or SCC.


6. Influence of scale on CaCO3 scale in fresh water. The CaCO3 scale layer is bad for heat transfer but good for corrosion prevention

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