Scales, sludges, inorganic deposits, and foulants

Corrosion takes many forms but is always an electrochemical process, whereas deposition and fouling are often combinations of both chemical and physical processes, involving inorganic and organic contaminants, the effective control of which tends to be much more of an art than a science. 

The development and ready availability in recent years of a wide range of modem polymeric deposit control agents (often with novel, multifunctional 

This term refers to the crystalline growth of a variety of insoluble salts or metal oxides, which are usually deposited as a hard adherent layer, or layers, on heat-transfer surfaces. This is extremely undesirable because all crystalline scales reduce the rate of heat transfer and therefore seriously reduce the efficiency of the overall cooling system. 

Scales from individual salts vary in their heat-transfer insulating effects, but most adherent deposits found on heat-transfer surfaces consist of one or two predominant salts (such as calcium carbonate or calcium phosphate) intimately combined with a variety of lesser amounts and types of scales, together with some corrosion debris and other fouling matter. 

Suffice it to say that a small buildup of scale generally produces a detrimentally large reduction in heat transfer. 

---