Cast Iron Material Properties & Maintenance

The Casting Process

Cast iron products are manufactured in sand moulds into which molten iron is poured. The moulds are created by imprinting the shape into a box of sand. Once filled with molten iron at the foundry, the mould is left to cool and solidify.

When cold, the casting is removed by breaking the sand away to reveal the cast item. Each mould can be used only once. Furnitubes manufacture products in two types of cast iron: GREY IRON and S.G. IRON (ductile iron).

4 bell bollards with yellow strips in a row

Grey Cast Iron

The most common general purpose cast iron

Manufacture is straightforward and it can easily be cast into intricate shapes. The graphite is present in large flat flakes within the crystal structure of the iron. These flakes behave like microscopic fault lines allowing cracks to propagate through an item when it is over-loaded. Because of this, grey iron is brittle and will not absorb a great deal of impact energy before failure. Grey iron will be the most economic choice for items that do not need to provide any structural or protective function.

Furnitubes cast iron and timber Eastgate bench in park

S.G. Ductile Iron

Can absorb significant impact energy

Spheroidal Graphite Cast Iron differs from grey iron in that carbon is present in different percentage proportions, in the form of spherical nodules rather than flat flakes. These nodules do not encourage crack propagation. S.G. Iron is ductile; deforming before it fails making it tough; able to absorb significant impact energy. The manufacturing process for S.G. Iron is complex and the casting process more difficult than grey cast iron. Consequently S.G. items are more expensive. S.G. cast iron should be used for structural items or where impact is likely.

Maintenance

Well maintained cast iron products have high corrosion resistance and longevity as demonstrated by early 18th century cast iron street furniture that can still be seen in many provincial towns and cities throughout Europe.

Unlike steel, unprotected cast iron can remain exposed to the elements for several years without undue effect on the products structural integrity. However, if the protective coatings are allowed to deteriorate, oxidation will occur and attempt to spread over the surface and will lift the paint or coating surrounding the damaged area. From a cosmetic point of view, it is therefore best to remove any oxidation with a wire brush and re-paint the damaged area to prevent the oxidation spreading. (Note: oxidation does not constitute a health and safety hazard).

Finish

If supplied as Primed finish:

Interseal 670HS – A low VOC, Two Pack high build, high solids surface tolerant epoxy maintenance coating. Semi-gloss

If supplied as Gloss finish:

Interseal 670HS – Two Pack Primer
Interfine 691 Two Pack epoxy acrylic isocyanate free cosmetic Gloss finish

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Cast iron

The Casting Process

Cast iron products are manufactured in sand moulds into which molten iron is poured. The moulds are created by imprinting the shape into a box of sand. Once filled with molten iron at the foundry, the mould is left to cool and solidify.

Grey Cast Iron

S.G. Ductile Iron

Maintenance

Well maintained cast iron products have high corrosion resistance and longevity as demonstrated by early 18th century cast iron street furniture that can still be seen in many provincial towns and cities throughout Europe.

Finish

Cast iron

The Casting Process

Cast iron products are manufactured in sand moulds into which molten iron is poured. The moulds are created by imprinting the shape into a box of sand. Once filled with molten iron at the foundry, the mould is left to cool and solidify.

Grey Cast Iron

S.G. Ductile Iron

Maintenance

Well maintained cast iron products have high corrosion resistance and longevity as demonstrated by early 18th century cast iron street furniture that can still be seen in many provincial towns and cities throughout Europe.

Finish

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