How to maintain and prevent corrosion of plate heat exchanger in application?
Knowing the causes of various corrosion of heat exchanger and reasonably selecting anti-corrosion measures can achieve the purpose of efficient utilization of equipment. According to the relevant corrosion conditions, the following anti-corrosion methods are proposed: corrosion inhibitors and electrochemical protection are mainly introduced here.
- Corrosion inhibitor
The corrosion inhibitor with chromate as the main component is commonly used in cooling water system. Chromate ion is an anode (process) inhibitor. When combined with appropriate cathode inhibitor, it can obtain satisfactory and economic anti-corrosion effect.
Chromate zinc polyphosphate: polyphosphate is used because it can clean the metal surface and has corrosion inhibition ability. Polyphosphate can be partially converted into orthophosphate. They can also form large colloidal cations with calcium to inhibit the cathode process.
Chromate zinc phosphonate: this method uses sodium phosphonate instead of polyphosphate. Similar to the previous method, carbamate can also be used in occasions with higher pH than that specified for polyphosphate. Dimethylaminophosphonate can prevent scale and control the precipitation of calcium salt even if the pH value is 9.
Chromate zinc hydrolyzed polyacrylamide: due to the dispersion of cationic copolymer hydrolyzed polyacrylamide, it can prevent or inhibit the generation of scale.
- Electrochemical protection
Cathodic protection and anodic protection are adopted. Cathodic protection uses an external DC power supply to turn the metal surface into a cathode to achieve protection. This method consumes a lot of power and costs a lot. Anode protection is to connect the protected heat exchanger to the anode of external power supply, so as to form a passive film on the metal surface, so as to be protected.
The above content is the electrochemical protection method of plate heat exchanger, which is of great help to the maintenance and anti-corrosion of plate heat exchanger.