Orthophosphate

As was mentioned previously, orthophosphate is an anodic inhibitor, which can provide the protection to mild steel surfaces. In certain situations, calcium and/or iron can react with orthophosphate to form calcium phosphate and ferric phosphate sludges, respectively. The solubilities of these compounds are inversely related to pH, orthophosphate concentration, calcium and/or iron concentration, and temperature. Since an increase in temperature induces the precipitation of these materials, the sludges formed are usually found first along heat transfer surfaces thereby, impeding the heat transfer process.