Problems Inherent to Water Contaminants

In addition to the first four problems, which are of water origin, oil leakage into the water also causes problems. Oil will interfere with other treatments employed. It is therefore desirable to eliminate oil leakage as much as possible by repairing leaks as soon as they develop. 

Oxygen, carbon dioxide and various chemicals used to reduce scaling can cause corrosion. Corrosion control is provided largely by the use of inhibitors such as chromates, polyphosphates, silicates and alkalies. 

Corrosion within the tower itself is due mainly to the particular conditions existing therein (air, humidity and temperature) and also to the chemical treatment of the water. All construction materials exposed to these conditions must be selected carefully. Hardware and piping for distribution headers have been successfully made with hot-dipped galvanized steel, cadmium-coated steel, stainless steel and silicon bronze. 

Scaling and corrosion are related phenomena. The properties of water influencing both are the calcium hardness, alkalinity, total dissolved solids, pH and temperature. Theoretically, the above conditions can be controlled so that the water is in equilibrium and neither corrosion nor scaling results. In practice, however, this equilibrium is difficult to achieve since it is a border condition, and a delicate balance must be maintained. 

The principal scale-forming material in cooling systems is calcium carbonate, which has a solubility of about 15 ppm and is formed by the decomposition of calcium bicarbonate. 

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