Ductile iron pipes are one of the materials used in modern urban water supply, property fire protection, and natural gas transportation. In practical applications, in order to improve corrosion resistance and extend the service life of products, galvanizing is quite important for them. Through galvanizing, a protective layer can be added to ductile iron pipes.
After years of repeated experiments on several materials, a cost-effective and suitable anti-corrosion material for ductile iron pipes has been found, which is zinc. The zinc spray layer of ductile iron pipes can actively maintain the pipeline through the electrochemical effect of zinc and iron, forming a stable maintenance layer.
During the process of touching the soil, the metal zinc on the surface of ductile iron pipes gradually transforms into a tight, adhesive, and continuous zinc salt layer. The asphalt paint coating on the outer layer appears to be the same as a thin film, making zinc an insoluble zinc salt instead of a soluble zinc hydroxide. One of the primary characteristics of the zinc spraying layer is the ability to actively repair and maintain the integrity of the maintenance layer at the damaged area, Zinc ions migrate to the damaged area through sealed pores to repair the wound and become a stable and insoluble spray.
In fact, besides galvanizing, there are many other anti-corrosion treatment methods for ductile iron pipes, such as asphalt paint coating, cement mortar lining+special coating, epoxy coal tar coating, epoxy ceramic lining, aluminate cement coating and sulfate cement coating, polyurethane coating, etc.
Different anti-corrosion treatment methods are suitable for ductile iron pipes in different situations. For example, asphalt paint coating is used for transporting gas pipelines. Preheating the pipes before painting can improve the adhesion of asphalt paint and accelerate drying. The internal anti-corrosion method of cement mortar lining+special coating is suitable for pipelines transporting sewage, which can improve the corrosion resistance of the lining.
Epoxy coal tar coating is suitable for both gas pipelines and sewage pipelines. It is a two-component coating that has high adhesion and a very lubricating appearance; Epoxy ceramics are only used when ductile iron pipes are used in sewage and gas pipelines, but due to the difficulty of production technology and high cost, there are certain limitations in their application.
If the surface of ductile iron pipes is coated with aluminate cement and sulfate cement, both are suitable for the internal anti-corrosion of ductile iron pipes used in sewage pipelines, improving their ability to resist the corrosion of acid and alkali components in sewage. Polyurethane coating is also a special type of coating, with the same anti-corrosion effect.
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