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Joel Hawkins
Quarry engineer
Asked a question last year

Why are Chrome Corundum Bricks Red in Color?

Why are Chrome Corundum Bricks Red?

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Why are Chrome Corundum Bricks Red in Color?


Chrome corundum brick :

let’s discuss some introductory part of Chrome corundum brick.

Introduction :

A brick which is a solid synthesized by high temperature melting and it is made up of a certain proportion of Alumina and Chrome oxide.

Chemicals in Chrome corundum brick :

  • Chrome oxide + Alumina

The colour of the above special type of brick depends upon the percentage of Chrome oxide in it.

  • 3% Chromium oxide – light red colour
  • 8% chromium oxide – purplish-red colour
  • More than 20% chromium oxide: black and red colour
  • Higher the percentage of chromium oxide then the colour of the above brick is very dark
Lillian Holmes
Director of Public Works


I am unable to understand what your point is, can you elaborate.

Manuel Mason
Purchasing Coordinator

Chrome corundum brick is initially formed in green colour. If the Cr2O3 content of chrome corundum brick is about 3%, the colour it will take is light red and the purplish-red colour is formed at about 8%. If the Cr2O3 content is more than 20%, the colour of the chrome corundum brick will appear black and red, higher the chromium content darker is the colour.

Henry Newman
Water resource engineer

“will not only not reduce the fire resistance of the material, but will increase the fire resistance of the material”.

This sounds like rubbish, please explain.

Dean Richards
Building control officer

Chrome Corundum Bricks are popular for having high temperature resistant and slag corrosion resistant, especially the corrosion resistant of molten cinders is more effective than low silicon corundum bricks. Chrome Corundum bricks generally contains Cr2O3 and the main mineral composition is Al2O3-Cr2O3 solid solution.

The appearence color of chrome corundum brick is green at initial stage of molding because it is made of corundum with chrome green. But due to high temperature sintering, its appearence color becomes red or sometimes even purple-red after reaction with CO. And the color change is determined by the level of chromium content plus the load-resistant softening temperature of these bricks are very high.

Chrome corundum bricks get a Ruby color (close to red) due to the hight content of chromium oxide as compared to alumina and other metals. If chromium oxide is present in a large amount and so are oxides of metals other than aluminium, the color will be a more deeper red. Else, it could be even grey or black depending on the composition.

Steve Mendoza
General practice surveyor

Chrome corundum brakes are composed of Cr2O3 and an Al2O3 which are heated at high temperature to form a solid solution which is red in colour. Chrome Corundum bricks composed of 9 % to 15% Cr2O3 which imparts high strength and durability to the bricks.

Terry Collins
Sustainability consultant
Why are Chrome Corundum Bricks Red in Color?


I added some technical points about Chrome corundum bricks

  • It is a new excellent grade refractory materials with a very high-temperature performance with strong corrosion resistance and high strength which is made up of chromium oxide and for corundum as a raw material which is mixed with some other additives.

Chemical composition:

Al2O3 —.   >92

CaO.        <1.2

SiO.          <1.0

Fe2O3.     <0.3

Cr2O7.     >3

ZrO2.        >3


Cold crushing strength >180 MPa

porosity.        >15%

Bulk density. > 3.25 g/cm^3

Modulus of rupture. > 9.5 MPa


  1. It is fire-resistant properties
  2. Strength in the range between 70 to 100 MPa.
  3. High resistance against thermal shocks
  4. Resistance against slag erosion