The natural corrosiveness of water varies with the impurities found in the raw water supply. One common indicator of corrosiveness is the level of pH. The more acidic the pH, the more corrosive the water. Other factors that can affect the corrosiveness of water are the quantity of dissolved minerals and gases, temperature, and velocity. Galvanic corrosion occurs when two dissimilar metals or alloys are connected and exposed to a corrosive environment. Pitting corrosion, or oxygen pitting, is a randomly occurring, highly localized form of attack on the metal surface and often is most destructive to the boiler or cooling system.
Corrosion also can be the result of microbiological organisms such as bacteria, fungus, and algae.
The growth of microbiological organisms in industrial and commercial cooling systems also can foul heat exchangers and cause odor problems. Cooling System Problems Power, process, and refrigeration systems all develop a sizable byproduct heat. Whether generated from a centrifugal or reciprocating refrigeration machine or an absorption machine, heat needs to be dissipated. Typically, this is accomplished by recirculating water through a cooling tower. Scale deposition, corrosion, microbiological growth, and fouling can cause problems in the cooling system's heat exchangers, water-carrying lines, and other system components.