Why is sea water not used in boilers?

Explanation

Sea water is hard water. It contains Mg`(HCO_(3))_(2)` and `Ca("HCO"_(3))_(2)`, which on boiling , form a hard heat insulating thick layer or scale of `"MgCO"_(3) and "CaCO"_(3)` on the inner surface of the boiler. Consequently, much heat is required to raise the temperature of the boiler and thus, fuel economy is adversely affected.
(2) Again at much higher temperatures, the boiler scales and the metal of the boiler expand unequally. Due to such uneven expansion, cracks are formed on the scales. When not water comes in contact with hot metal surface of the boiler through these cracks, it is suddenly converted into steam. Due to the high pressure, thus developed , the boiler may burst leading to accidents. Again, Mg`Cl_(2) and "MgSO"_(4)` present in sea water undergo hydrolysis to form HCl and `H_(2)SO_(4)` which degrade the metallic component of boiler. So, sea water is not used in boilers.