Ductile iron pipes have become one of the materials currently unavailable. These pipes are indispensable for projects like urban water supply and natural gas transportation. To enhance the corrosion resistance of ductile iron pipes in practical applications, a series of measures will be taken. Here's an explanation that can be given to the manufacturers: On one hand, galvanized ductile iron pipes can extend the product's lifespan by actively repairing the damaged layer and maintaining the integrity of the repair. Moreover, zinc ions migrate to the damaged area after closing the pores, healing the wound, and then transform into a stable, insoluble spray. Of course, in addition to galvanized ductile iron pipes, there are many other corrosion prevention methods, such as asphalt coatings and epoxy coal tar coatings, which are also effective. The corrosion prevention methods for ductile iron pipes vary depending on the application. The asphalt coatings mentioned above are primarily for gas pipelines. It is also important to emphasize that epoxy coal tar coatings are a two-component coating, suitable not only for gas pipelines but also for sewage pipelines!
The gas pipeline is coated with asphalt. Preheating the pipeline after spraying enhances the adhesion of the asphalt paint and accelerates drying. A special cement mortar coating is suitable for sewage pipelines, improving the corrosion resistance of the material. Epoxy coal asphalt coatings are used for gas and sewage pipelines. It is a two-component coating with high adhesion and a very smooth surface. Epoxy ceramic coatings are suitable for both sewage and gas pipelines. However, due to the high manufacturing difficulty and cost, there are certain limitations in its application. Epoxy ceramic coatings have high adhesion and a smooth surface, while spheroidal cast iron pipes are an excellent corrosion-resistant coating. Aluminate cement coatings and sulfate cement coatings are both suitable for the internal corrosion protection of spheroidal cast iron pipes used in sewage pipelines, enhancing the resistance to acidic and alkaline components in the sewage. Polyurethane coatings are a new type of green special coating developed to meet environmental protection requirements, offering good wear and corrosion resistance.
In daily production and operation, how can we enhance the anti-corrosion properties of ductile iron pipes? To fundamentally improve the performance of the pipelines, we must understand their inherent structural characteristics. A survey of ductile iron pipes in over a dozen typical Chinese cities revealed that the static leakage rate of urban water supply networks reaches 12-13%, far exceeding the national standard of keeping the leakage rate below 6%. Therefore, the anti-corrosion of ductile iron pipes has always been a pressing issue that needs to be addressed.
To enhance the anticorrosion properties of ductile iron pipes, it is crucial to apply an anticorrosive layer externally over the zinc coating. This effectively reduces corrosion. For ductile iron pipes, to date, the external protection using zinc and asphalt should be the best and most fundamental material. For pipeline installations in areas with strong corrosivity, additional protective measures can be taken by applying methods such as polyethylene sheathing or polyurethane coating, or polyethylene coating over the fundamental protective layer for special maintenance.
