ConceptsTechnology

What is Corrosion Control?

It refers to the corrosion control of steel water pipes

The metal surface undergoes a chemical reaction or an electrochemical reaction under the action of the surrounding medium, and the damage is called corrosion Corrosion makes the inner wall surface of the pipe rough and increases the head loss of the water flow , increasing the cost of water supply Accumulation of corrosion products reduces the cross section of the pipeline, which reduces the water supply capacity of the pipeline In severe cases, the wall of the pipeline is perforated and the section of the pipe is damaged, causing the water to stop for maintenance

The cause of the corrosion is related to the characteristics of the surface material and the nature of the surrounding medium.

Microorganisms that multiply on the metal surface can promote corrosion Factors that affect the corrosion rate of the inner wall of the pipe include dissolved oxygen, carbon dioxide, chloride ions, sulfate ions, total dissolved solids content , pH, temperature, flow rate, etc. The factors that affect the corrosion of the outer wall of the tube are humidity, pH value and electrical conductivity.

The main methods to control corrosion of water pipes are: adding a protective layer or protective film to protect the inner wall of the pipe; adopt cathodic protection to protect the outer wall of underground pipes (see maintenance of the water supply network); Adding corrosion inhibitors in water, commonly used in circulating cooling water system, not only protects the inner wall of the pipeline, but also protects the surface of the heat exchange equipment in contact with water; Use corrosion-resistant pipes, such as galvanized steel pipes, plastic pipes, and fiber cement pipes

In the open type circulating cooling water system, since the dissolved oxygen is replenished when the cooling water passes through the cooling tower or swimming pool, and the dissolved solid concentration of the water is high, the water is very corrosive

Corrosion control has become one of the main contents of circulating cooling water treatment (see Circulating Cooling Water System) The main treatment method is to add corrosion inhibitor Its main function is to inhibit the electrochemical process in corrosion Corrosion inhibitors are divided into anode corrosion inhibitors, cathode corrosion inhibitors and bipolar corrosion inhibitors

Anodic corrosion inhibitor inhibits the anodic reaction of the corrosion process; cathodic corrosion inhibitor inhibits the cathodic reaction of the corrosion process; bipolar corrosion inhibitor simultaneously inhibits the anodic reaction and the cathodic reaction of the corrosion process

Commonly used corrosion inhibitors are chromate, polyphosphate, phosphonate, silicate, molybdate, tungstate, nitrite, zinc salt, benzothiazole, organic amine, tannin, lignin, etc. Adding two or more corrosion inhibitors at the same time can take advantage of their synergistic effect to reduce the amount of medicine

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