Can fire bricks be used for acid resistance?

No. Fire bricks are porous so that they stay stable at high temperature, and acid soaks into them and attacks the body. For acid service, acid proof bricks to IS 4860 are used.

Can acid proof bricks be used in a furnace?

No. Acid proof bricks are made for chemical resistance, not furnace temperatures. They are used up to 900 C in chimney flues and ducts when laid in potassium silicate mortar, but furnaces need refractory fire bricks.

Which brick should be used for hot acid?

For hot acid service, acid proof bricks laid in potassium silicate mortar are used for temperatures up to 900 C. For hydrofluoric acid or fluorides at any temperature, carbon bricks are used.

What is the difference between acid proof bricks and acid proof tiles?

They have the same dense, vitrified body. Acid proof tiles are 10 mm to 30 mm thick for floors, drains and lighter duty, and acid proof bricks are 38 mm or 75 mm thick for vessels, tanks, pits and heavy duty floors.

Are acid proof bricks refractory bricks?

No. Acid proof bricks have good thermal durability and are used up to 900 C in the right mortar, but they are chemical resistant bricks, not refractory furnace bricks.

Acid Proof Bricks vs Fire Bricks: Differences Explained

Acid Proof Bricks vs Fire Bricks

Acid proof bricks are made to resist chemical attack. Fire bricks, also called refractory bricks, are made to resist high temperature. A fire brick in an acid tank is eaten away, and an acid proof brick in a furnace does not hold up to furnace temperatures. Where heat and acid occur together, acid proof bricks are laid in potassium silicate mortar for service up to 900 C.

Side by Side

	Acid proof bricks	Fire bricks (refractory)
Made to resist	Acids, alkalis and solvents	High temperature and flame
Body	Dense, vitrified, low iron clay	Refractory clay or alumina, usually more open
Water absorption	2% maximum (IS 4860 Class I)	Higher, because the body is more porous
Compressive strength	700 kg/cm² minimum	Varies by grade
Temperature	Up to 900 C when laid in potassium silicate mortar	Furnace temperatures well above 1,000 C
Typical use	Acid tanks, reaction vessels, pickling tanks, pits, process floors, flue ducts	Furnaces, kilns, boilers, ovens
Mortar	Chemical resistant mortar to IS 4832	Refractory mortar or castable

Why a Fire Brick Fails in Acid Service

A fire brick is built to stay stable at very high temperature, which needs an open, porous structure. That porosity lets acid soak into the brick, where it attacks the body from inside. A lining built from fire bricks in an acid tank loses strength quickly and starts leaking at the joints and through the brick itself.

Why an Acid Proof Brick Is Not a Furnace Brick

An acid proof brick is fired to a dense, vitrified body so that liquid cannot enter it. That density is what makes it chemically resistant, but it is not designed for direct flame or furnace temperatures. In chimney flues, scrubbers and ducts where hot acid gas is present, acid proof bricks are laid in potassium silicate mortar, which carries the system up to 900 C.

Acid Refractory Bricks: a Common Confusion

Some buyers search for "acid refractory bricks" or "acid resistant fire bricks". In most cases what they need is an acid proof brick to IS 4860 for a chemical duty, laid in the right mortar. If the service involves both very high temperature and acid, send us the temperature and the chemistry and we will recommend the combination.

Acid Proof Bricks vs Acid Proof Tiles

Both are made from the same type of dense, vitrified body. The difference is thickness and duty:

Acid proof tiles are 10 mm to 30 mm thick, used for process floors, drains, walls and lighter duty tank lining. See acid proof tiles.
Acid proof bricks are 38 mm and 75 mm thick, used for vessels, tanks, pits, chimneys and floors under heavy load, impact or thermal shock. See acid resistant bricks.

For hydrofluoric acid and fluorides, neither is suitable, and carbon bricks are used.