Scale and deposit formation

In areas of deposit formation, dissolved solids, specifically Calcium and magnesium hardness constituents can precipitate from cooling water as the temperature increases. Deposits accumulate on the heat transfer surfaces as sulphates and carbonates, the magnitude of which is dependent on the water hardness, the dissolved solid content, local temperatures and local flow characteristics. Scales can reduce heat transfer rates and lead to loss of mechanical strength of component parts, this can be exacerbated by the presence of oils and metal oxides.

Calcium Carbonate

Appears as a pale cream, yellow deposit formed by the thermal decomposition of calcium bi-carbonate ;
Ca(HCO3)2 + Heat becomes CaCO3 + H2O + CO2

Magnesium Silicate

A rough textured off-white deposit found where sufficient amounts of Magnesium are present in conjunction with adequate amounts of silicate ions.Silicate deposit is a particular problem for systems which utilize silicate additives for corrosion protection. This is typical of system with aluminum metal in the cooling system. The silicate forms a protective barrier on the metal surface. A high pH (9.5 - 10.5) is required to keep the silicate in solution. In the event of sea water contamination or some other mechanism that reduces the pH the silicate is rapidly precipitated and gross fouling can occur.

Copper

The presence of copper within a cooling system is very serious and it can lead to aggressive corrosion through galvanic action. Specific corrosion inhibitors are contained with cooling water system corrosion inhibitors.