Corundum is considered to be the most important synthetic abrasive and does not contain iron. It consists, among other things, of aluminium oxide and silicon dioxide. Silicic acid only exists in bounded form. Because it can be produced with different Al2O3–contents – by this the hardness can be varied – it can be used for different kinds of work. Furthermore, corundum is supplied in various qualities. Difference is made between an inexpensive regenerate, electro corundum and expensive high grade corundum.
Corundum can be used for recycling uses. Due to its hardness normal corundum of medium quality can be used about 20 – 25 times in rotation. This reduces the necessary amount of abrasives to about 1/20 compared to slag abrasives. Also after several runs the angular corundum does not lose its shape. Due to its geometry it is not suitable for applications in shot-blasting wheels.