Heat exchanger corrosion protection
Corrosion inhibitors based on chromate are commonly used in cooling water systems. Chromate ions are an anode (process) inhibitor, when combined with a suitable cathode inhibitor, is satisfactory and economical Anti-corrosion effect.
Chromate-zinc-polyphosphate: Polyphosphate is used because it has a clean metal surface and has corrosion inhibition ability. Polyphosphate can be partially converted into orthophosphate, which can also form colloidal cation with calcium and inhibits the cathode process.
Chromate-zinc-phosphonate: This method is similar to the previous method except that sodium phosphonate is used instead of polyphosphate. Carbamyl phosphate can also be used for the pH specified by polyphosphate for high occasions. The carbamate phosphonate prevents scale formation and controls the precipitation of calcium salts even at a pH9.
Chromate-zinc-hydrolyzed polyacrylamide: Due to the dispersion of the polyacrylamide hydrolyzed by the cationic copolymer, it is possible to prevent or inhibit scale formation.
Electrochemical protection: Cathodic protection and anode protection. The cathodic protection uses an external DC power source to make the metal surface become a cathode to achieve protection. This method consumes a large amount of electricity and is expensive. The anode protection is to protect the heat exchanger from the anode of the external power supply to form a passivation film on the metal surface to protect it.