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  • What is Porosity?

What is Porosity? - an explanation by Impregnation Services Ltd

Porosity

Porosity is a sponge-like area in an otherwise sound metal part. There are three basic types of porosity: enclosed, blind or through porosity.

• Enclosed porosity is completely isolated within the wall thickness of a part.
• Blind porosity is connected to only one side of the part wall.
• Through porosity completely extends through the wall thickness of a metal part, causing a leakage path.
• Size - what you see on the surface isn't always what you get.

When castings are machined, both blind and enclosed porosity are often opened-up, becoming continuous porosity and allowing leakage.

Porosity can be found in any type of metal casting or part and is a particular problem in castings made from aluminium, zinc, bronze, iron, magnesium and other alloys.  Porosity is always present in powdered or sintered metal parts.

In recent years the metal casting process has been greatly advanced, however, porosity, folds, inclusions and gas bubbles remain an inherent by-product of the casting process.  These by-products, while not detrimental to the structural integrity of a casting, may lead to product failures based upon the components inability to retain gas or fluids under pressure.