Basic principles for corrosion protection of standby boilers

Thread Content

There are many methods for preventing corrosion in boilers that are out of service, but the basic principles are essentially as follows: (l) Prevent air from entering the water and steam system of boilers that are not in use. Such as maintaining a certain steam pressure or feedwater pressure inside the boiler. (2) Keep the metal surface of the boiler equipment that is on standby fully dry. If hot, pressurized water drainage is used, drying can be achieved by utilizing the residual heat in the furnace or by using hot air from an adjacent operating boiler. Practice has shown that corrosion can be prevented when the relative humidity inside standby boiler equipment is below 20%. (3) Form a protective or adsorptive film on the metal surface that provides corrosion resistance. Corrosion protection can be achieved by using vapor-phase corrosion inhibitors such as cyclohexylamine carbonate after shutting down the furnace and draining water. (4) Immerse the metal surface in an aqueous solution containing a deoxidizer or other protective agent. Such as immersion in hydrazine or ammonia solutions. (5) Fill the standby boiler equipment with inert gas. Such as filling with high-purity nitrogen or ammonia. In fact, the aforementioned principles can be summarized as preventing electrochemical corrosion by eliminating cathode depolarizers to cause cathode polarization, forming stable protective or adsorptive films to cause anode polarization, or ensuring that there is no electrolyte solution on the metal surface.