1. Internal Treatment: 3) Carbonate Conditioning :
Scale formation can be avoided by adding sodium carbonate to boiler water.
CaSO4 + Na2CO CaCO3 + Na2SO4

2. Internal Treatment: 4) Calgon Conditioning :
It involves the addition of calgon or sodium hexametaphosphate to boiler water.
This substance reacts with calcium ions and forms highly soluble complex and thus prevents the precipitation of scale forming salt.
2CaSO Na2[Ca2(PO3) 6]
Na2[Na4(PO3) 6] Na2SO4

3. Internal Treatment: 4) Treatment with sodium aluminate :
When sodium aluminate is treated with boiler water, it gets hydrolyzed give sodium hydroxide and a gelatinous precipitate of aluminum hydroxide.
NaAlO2 + 2H2O NaOH + Al(OH)3
2NaOH + MgCl Mg(OH)2 + 2NaCl
Al(OH)3 and Mg(OH)2 entrap finely suspended and colloidal impurities like sand, oil drops and settle to the bottom and can be removed easily.