Classify Ductile Iron Products Based On Internal And External Coatings

Classify ductile iron products based on internal and external coatings as follows:

1. Common coating

Ordinary portland cement mortar is coated internally while zinc and bituminous paint is painted externally.

2. The internal coating of sulfate cement mortar

Sulfate cement, also known as high sulfate-resistant cement, has a good sulfate corrosion resistance and a wide application in transporting some highly corrosive mediums such as seawater.

 3.The internal coating of aluminate cement mortar

The ductile iron pipe for sewer line complying with ISO7186, EN598 and GB/T26081 is coated with aluminate cement (also known as high-alumina cement) internally, with a result of excellent resistance to chemical corrosion and abrasive resistance which is much more suitable for transporting rainwater, sanitary sewage and some kinds of industrial sewerage water.

4.Zinc-Aluminum coating

The outside surface of cast iron pipe is coated with Zinc- Aluminum coating (85%Zn+15%Al) weighed 400g/m2, which is suitable for soil with higher corrosivity.

5. The internal coating of epoxy ceramic

The interior of epoxy ceramic is made of epoxy resin, quartz powder and others with a dry film thickness of more than 1000μm, and the excellent corrosion resistance electrical insulating property makes it be a preferential position in transporting municipal sewage, reclaimed water, etc.

6. Epoxy resin seal coating

The cast pipe with epoxy resin sealing coating is equal to a cement inner-lining coated by a layer of epoxy resin sealing, whose thickness is determined in accordance with the characteristics of transmission medium, and has wonderful abrasive resistance and corrosion resistance. Thanks to the seal coating, the precipitation of hazardous substance is effectively resisted, commendably avoiding the pollution to transmission medium and more suitable for the direct delivery of drinking water.

7. Polyurethane coating

Polyurethane coating is made of bi-component polyurethane materials to a scale, and not only does it serve as the inner- lining material of nodular cast iron pipe, but as related outer erosion resistant coating. Polyurethane coating has many advantages such as wonderful abrasive resistance, excellent corrosion resistance, non- permeation, smooth surface, small resistance coefficient, few volatile organic compound, remarkable environmental protection property, etc. Some polyurethane coatings with a thickness above 900μm are mainly applied to transporting corrosive mediums or the mediums with high sanitary condition, including soft water, desalination seawater, municipal waste water, industrial waste water, and others; and some with thickness above 700μm are mainly applied to the soil environment with strong corrosivity such as the soil polluted by industrial waste water or with low specific resistance.