Ductile Iron is a high-performance material widely used in the pipe industry, distinct from traditional cast iron due to a specific metallurgical structure.
Structure and Properties
Ductile iron is produced by adding a small amount of magnesium to molten iron, which causes the carbon (graphite) within the material to solidify into spherical nodules or spheres, rather than the sharp, flaky structure found in gray cast iron.
This unique spheroidal graphite structure provides the material with its exceptional properties:
Ductility and Flexibility: Unlike brittle gray iron, ductile iron can be bent, twisted, or deformed significantly without fracturing, allowing it to withstand earth shifting, high impact, and water hammer.
High Strength: It possesses tensile and yield strengths comparable to certain grades of steel.
Relevance to Galvanizing
While ductile iron pipes are generally used for large-scale water, sewage, and gas transmission and typically feature internal linings (like cement mortar) and external coatings (like asphalt or loose polyethylene sleeving), zinc coating is a standard external corrosion protection measure specified in international standards (e.g., ISO 8179)
The zinc is applied to the ductile iron pipe surface to provide cathodic protection, ensuring the longevity and reliability of buried pipelines.