Two Anti-corrosion Measures Used in General Industrial Boilers

There are two commonly used anti-corrosion measures for industrial boilers: dry method and wet method.

01 Dry Maintenance

The principle of dry maintenance is to keep the pot free of moisture. The specific method is first to clean the scale, mud and rust in the pot, open the manholes and hand holes, dry the inside of the boiler, or light a minimal flame with a wooden stick on the grate to dry the inside of the boiler. Then place the uncovered non-metallic container containing the desiccant into the pot, and then tightly close all valves, water doors, manholes, and hand holes to prevent air from entering and keep the internal surface of the boiler dry for a long time. In order to prevent external corrosion due to condensation of water vapor on the outer surface of the pot, you can bake it with minimal heat (or put a desiccant) at intervals. Desiccant generally uses anhydrous calcium argon, quicklime or silica gel. Each cubic meter of volume needs to add (1~2)kg anhydrous calcium oxide, (2~3)kg quicklime or (1.5~3.0)kg silica gel. After the desiccant is put into the pot, it should be checked every three months or so and the failed drying chips should be replaced in time. Before starting the fire, just remove the container containing the desiccant. Close the manhole, fill in water according to regulations, and start the fire. Dry maintenance is suitable for boilers that have been out of service for a long time.

02 Wet Maintenance

The principle of wet maintenance is to prevent the oxygen in the water in the pot from interacting with the metal surface.

When the pot is filled with an alkaline solution of a certain concentration, a protective layer of alkaline bubbles will be generated on the metal surface to protect the metal from corrosion. The specific method of wet maintenance is the same as that of dry maintenance. The scale and iron in the pot should also be cleaned, and then the attenuating solution should be added. Before adding liquid, all relevant valves should be checked and closed tightly to prevent alkaline solution from entering the operating system. Raise low heat, keep the outside of the boiler dry, and heat the water in the pot to (80~100)°C. As the solution is heated, convection occurs, so that the concentration of the solution in the pot can be equalized. Check the pH value of the pot water every 5 days, and control it to be 10 to 12. If the alkalinity is low, add more alkali solution. Warm maintenance is suitable for boilers that are out of service for a short period of time. Wet maintenance is not suitable in areas with low temperatures.