Before spraying, the surface of ductile iron pipes must be dry and free of rust, attached particles, oil, and other foreign matter. Unlike SML pipes, ductile iron pipes do not require sandblasting pretreatment due to the inherent properties of the material. Ductile iron pipes, through a spheroidization process that distributes the graphite in a spherical shape, possess excellent mechanical properties, with tensile strength exceeding 420 MPa and elongation between 7% and 10%, significantly superior to ordinary cast iron pipes. This structure imparts enhanced corrosion resistance, especially after applying a zinc coating (>130 g/m²) and an epoxy resin finish, creating a dual-protection system that eliminates the need for sandblasting.
The socket of the ductile iron pipe is coated with zinc spray and asphalt, and must pass the non-toxic certification. The overall protection structure of the pipeline is a galvanized layer with a finishing coating, as follows:
- Zinc coating: Common specifications are 130g/m² and 200g/m², with a zinc content of 99.9%. Zinc-aluminum alloy coatings offer more stable performance and enhanced corrosion protection, with coating weights up to 400g/m².
Note: Zinc coating thickness affects cost; thicker zinc coatings increase cost and improve corrosion protection.
- Finishing coatings: Mainly include asphalt and synthetic resin.
Asphalt coating thickness is typically around 70µm (asphalt paints are generally expressed by thickness rather than weight per unit area).
Common types of synthetic resin topcoats are PU (polyurethane) and PE (polyethylene).
SML cast iron pipe, ductile iron pipe coating, cement lined ductile iron pipe, PU coating ductile iron pipe, socket ductile iron pipe
Post time: Sep-25-2025
