① Corrosion inhibitors Corrosion inhibitors containing chromate as the main ingredient are commonly used in cooling water systems. Chromate ions are an anodic (process) inhibitor that, when combined with a suitable cathodic inhibitor, Satisfactory and economical anti-corrosion effect. Chromate-Zinc-Polyphosphate: The use of polyphosphate is due to its role in cleaning the surface of the metal, corrosion resistance, polyphosphate can be partially converted to orthophosphate, they can also be produced with calcium Of colloidal cations that inhibit the cathodic process. Chromate-Zinc-Phosphonate: This method uses sodium phosphonate instead of polyphosphate. Similar to the previous method, aminomethylene phosphate can also be used for the pH value of the polyphosphate High occasion. Amino methylene phosphonates can prevent scale, even if the pH value of 9 can control the precipitation of calcium salt. Chromate-Zinc-Hydrolyzed Polyacrylamide: It is possible to prevent or inhibit the generation of fouling into scale due to the dispersion of the polyacrylamide hydrolyzed by the cationic copolymer. ② electrochemical protection using cathodic protection and anode protection. Cathodic protection is the use of external DC power supply, so that the metal surface into the cathode to achieve protection, this method power consumption, high cost. Anode protection is the protection of the heat exchanger connected to the external power supply anode, so that the metal surface to generate passivation film, which is protected.