Factors Making Corrosion in Cooling Towers

As you know, the cooling tower is used to cool the circulating water of HVAC equipment such as chillers, mini chillers, etc., and to cool industrial equipment and processes. Cooling towers are produced and supplied in different shapes and capacities, and in terms of cooling performance, they are divided into two categories: open circuit (water-cooled or water-cooled) and closed circuit (air-cooled or air-cooled), each of which has its characteristics. They are special to themselves.

In the open circuit cooling tower, the water flowing on the packings and tower boards is cooled by spraying water from the top of the tower and its direct contact with the air; But the temperature of the water in the closed circuit cooling tower or air cooling is indirectly reduced by spraying the cooling water on the coil containing the hot fluid.

Each type of open-circuit and closed-circuit cooling tower is suitable for its conditions. You can contact the specialized group of heating equipment to identify and choose each type of cooling tower and get advice from the experts of the air conditioning unit.

As mentioned, the activity of cooling towers is based on the use of water; For this reason, the metal surfaces and pipes of the cooling tower are constantly in contact with water and are subject to corrosion depending on the quality of the water. Corrosion, especially in the type of galvanized cooling tower, causes damage to various parts of the device and reduces its efficiency; Also, corrosion in the cooling tower requires spending a lot of money for repairs, that's why it is very important to pay attention and control it.

As mentioned, corrosion in the cooling tower is caused by water, and for this reason, its amount depends on the properties of the water. These characteristics include things such as water TDS, water hardness, water pH, residual chlorine concentration, accumulation of aggressive ions, etc., which we will explain in the rest of the article, please stay with us until the end of the article.

Effect of water TDS on cooling tower corrosion

TDS is an indicator for measuring the total dissolved solids in water and represents the total hardness of the water. Also, TDS represents the electrical conductivity of water, and its value is measured by an electrical conductivity meter (TDS meter), with units of milligrams per liter. As this number increases, the percentage of corrosion in the cooling tower will increase, so to prevent corrosion in the cooling tower, the TDS value of the water should be minimized.

For this purpose, it should be solved by using methods such as filtration methods (generally RO method), using softeners (in resin and electromagnetic types), adding chemicals, and using anti-scaling agents.

The effect of water hardness on cooling tower corrosion

Water hardness is the amount of calcium and magnesium in water, which is the cause of sedimentation in the cooling tower, and is measured using a hardness kit in a TDS meter. The difference between water hardness and TDS is in the amount of its salts; In this way, TDS represents the total hardness of water, but hardness only shows the amount of calcium and magnesium ions in water. To reduce water hardness, resin softeners or inhibitors should be used to prevent the accumulation of sediments and corrosion in the cooling tower.

Effect of Water pH on Cooling Tower Corrosion

The pH of the water shows the acidity or alkalinity of the water and is one of the most effective parameters for corrosion in the cooling tower. The pH of water is measured by a pH meter and its range is between 0 and 14. If the number indicating the pH meter is less than 7, the water is acidic, and when it is in the range of 7 to 14, the water is alkaline. If the water in the cooling tower has a pH below 7 and is acidic, the cooling tower will be more exposed to corrosion; Therefore, paying attention to this issue and controlling the acidity or alkalinity of cooling tower water is of great importance.

Effect of Residual Chlorine Concentration in Cooling Tower Corrosion

To disinfect and remove sludge and algae, chlorine compounds such as sodium hypochlorite, chlorine gas, liquid chlorine, etc. are used in cooling tower water.

Normally, the concentration of chlorine added to the cooling tower water is 0.3 to 1 ppm, but if the chlorination process is not properly controlled, the concentration of chlorine increases to several ppm; If the chlorine concentration exceeds 2 ppm, the corrosion rate of the cooling tower, especially the carbon steel material, increases effectively. Therefore, in this situation, corrosion inhibitors should be used to control the corrosion of the cooling tower so that it is not subject to serious damage.

The effect of the accumulation of aggressive water ions on the corrosion of the cooling tower

Aggressive ions are ions such as chloride ions and sulfate ions, which weaken and destroy the barrier protective layer in high concentrations. The inhibitor with zinc salt structure is less affected by attacking ions than other inhibitors.

Effect of water temperature on cooling tower corrosion

The temperature parameter is one of the factors affecting the corrosion of the inner surfaces of copper pipes in the closed circuit cooling tower. If the inhibitors are not used, the corrosion in the closed circuit cooling tower increases in proportion to the increase in water temperature in the range of 25 to 50 degrees Celsius and then remains almost constant at temperatures above 50 degrees Celsius (polyphosphate inhibitors at temperatures More than 40 degrees Celsius, it almost loses its inhibitory properties.

The use of bivalent metal salts of phosphates in the temperature range of 30 to 50 degrees Celsius can be a suitable inhibitor to control corrosion and sediment formation.

Effect of water flow rate on cooling tower corrosion

The speed of water flow is one of the factors affecting the corrosion of the inner surfaces of the closed circuit cooling tower coil; The reason is the increase in water solubility with oxygen, which happens due to the high speed of water flow. Also, with the presence of inhibitors in the cooling tower, increasing the speed increases the effect of the inhibitor on the metal surface and increases the corrosion rate.

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Final word

In this article, we talked about the factors affecting corrosion in the cooling tower and we saw that parameters such as TDS, water hardness, PH, residual chlorine concentration, accumulation of aggressive ions, temperature, and water flow rate in the corrosion rate of cooling towers. are effective and by controlling each of them, the corrosion of the cooling tower can be prevented; We hope that we have provided you with useful information in this article.

To view and compare the types of cooling towers with different brands and capacities, as well as to know the updated prices of the products, go to the site of Dematheheez specialized collection (the first and most reliable specialized collection in the field of building installation equipment and all air conditioning devices since 1383 and has 3 valid business licenses) refer to; To get additional information during office hours, call 021-88822550 and get advice from the experts of the air conditioning unit of the specialized group of DamaTajhiz HVAC.

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