Main types & applications of acid-resistant bricks

Acid-resistant bricks are a type of special ceramic brick with excellent acid corrosion resistance. Both their composition and applications are designed to meet the requirement of “resisting the erosion of acidic media”, and they are widely used in industrial high-temperature anti-corrosion fields.

I. Raw Materials of Acid-Resistant Bricks

Acid-resistant bricks are products with a dense structure and low porosity, formed through high-temperature sintering, with their core components consisting of “acid-resistant matrix + acid-resistant binder”.

1. Main Raw Materials of Acid-Resistant Bricks

Raw materials are the core determinant of the acid resistance of acid-resistant bricks, accounting for more than 80% of the total composition. They are mainly composed of natural acid-resistant minerals and artificial acid-resistant materials.

• Silica Raw Materials: The most common raw materials for acid-resistant bricks, such as quartz sand, quartzite, and fused quartz, with silicon dioxide (SiO₂) as the main component. SiO₂ has stable chemical properties; except for hydrofluoric acid (HF) and hot phosphoric acid, it can resist the erosion of most acidic media (sulfuric acid, hydrochloric acid, nitric acid). Additionally, it is low in cost, making it the main raw material for mid-to-low-end acid-resistant bricks.
• Alumina Raw Materials: Materials such as high-alumina bauxite and corundum (α-Al₂O₃), with aluminum trioxide (Al₂O₃) as the main component. Al₂O₃ has better acid resistance than SiO₂, and also features high temperature resistance (able to withstand temperatures above 1000°C) and high mechanical strength. It is often used in mid-to-high-end acid-resistant bricks (high-alumina acid-resistant bricks) and is suitable for harsh conditions with strong corrosion and high temperatures.
• Other Acid-Resistant Minerals: For example, feldspar (used to adjust the sintering temperature and reduce brick shrinkage) and zircon sand (ZrSiO₄, which enhances resistance to hydrofluoric acid and high temperatures and is used in special acid-resistant bricks).

2. Binders of Acid-Resistant Bricks

Binders are used to bond the particles of acid-resistant framework raw materials into an integral structure. Meanwhile, they must possess acid resistance to avoid being damaged by acidic media themselves.

• Inorganic Binders: The mainstream choice for industrial acid-resistant bricks, such as sodium silicate (water glass), aluminum phosphate, and aluminum sulfate. After reacting with raw materials, these binders form acid-resistant vitreous bodies or ceramic phases, and contain no volatile harmful substances. They are suitable for scenarios where long-term contact with acidic media is required.
• Organic Binders: Materials like phenolic resin and epoxy resin, which are only used in special scenarios (anti-corrosion surfaces under low temperatures or non-long-term immersion conditions). The acid resistance of organic binders is limited by temperature (usually not exceeding 150°C), and they may age after long-term use. Therefore, organic binders are rarely used in industrial anti-corrosion applications.

3. Auxiliary Materials of Acid-Resistant Bricks

Auxiliary materials are added in small amounts to optimize the performance of acid-resistant bricks, usually accounting for less than 5% of the total composition.

• Sintering Aids: Such as talc powder and boric acid. They reduce the sintering temperature of acid-resistant bricks, minimize brick deformation, and ensure structural compactness.
• Anti-Cracking Agents: Such as silicon carbide and silicon nitride. They enhance the thermal stability and impact resistance of acid-resistant bricks, preventing cracking caused by temperature fluctuations or external forces.

II. Main Applications of Acid-Resistant Bricks

The core value of acid-resistant bricks lies in their “anti-corrosion + wear resistance + easy maintenance” properties. They are mainly used in industrial scenarios where contact with acidic media is involved, as well as in some special civil scenarios.

1. Chemical and Metallurgical Industries

• Application: Acid-resistant bricks are used for floors/walls of chemical workshops, linings of acid-base storage tank facilities, anti-corrosion layers around reaction kettles, pickling tanks in metallurgical plants, and linings of electrolytic cells.
• Functions: Acid-resistant bricks can resist long-term immersion or spraying of highly corrosive media such as sulfuric acid, hydrochloric acid, nitric acid, and chromic acid. Meanwhile, they can bear the heavy load of equipment and foot traffic (featuring wear resistance).
• Typical Cases: Chemical fertilizer plants (ammonium sulfate production workshops), electroplating plants (pickling and derusting stations), and iron and steel plants (cold-rolled steel plate pickling lines).

2. Environmental Protection and Water Treatment Industries

• Application: Acid-resistant bricks are used in sewage treatment plants (linings of acidic wastewater treatment tanks and neutralization tanks), waste incineration plants (inner walls of flue gas desulfurization towers and desulfurization slurry tanks), and electronics factories (acid-containing wastewater discharge ditches).
• Functions: Acid-resistant bricks can resist long-term erosion by low-concentration acidic wastewater and have a certain degree of impermeability (to prevent sewage from seeping and polluting the soil). Additionally, their smooth surface allows for easy cleaning (to prevent dirt accumulation and bacterial growth).
• Typical Cases: Municipal sewage treatment plants (pH adjustment tanks), and semiconductor factories (acidic fluoride-containing wastewater treatment systems, which require special acid-resistant bricks that are resistant to hydrofluoric acid).

3. Pharmaceutical and Food Industries

• Application: Acid-resistant bricks are used in pharmaceutical factories (floors of acidic bulk drug production workshops, cleaning tanks) and food processing plants (acidic food processing areas, such as around fermentation tanks in vinegar factories and fruit juice factories).
• Functions: In addition to acid resistance, they must comply with food-grade/pharmaceutical-grade hygiene standards (no heavy metal leaching, non-porous surface for easy disinfection) to prevent product contamination.
• Typical Cases: Vitamin C production workshops (sections using sulfuric acid as a raw material), and fruit vinegar brewing factories (anti-corrosion layers at the bottom of fermentation tanks).

4. Laboratories and Scientific Research Institutions

• Application: Acid-resistant bricks are used for the floors of chemical laboratories, linings of fume hoods, countertops of acid-base reagent storage cabinets, and corrosion test platforms in universities/scientific research institutes.
• Functions: They can withstand the mixed erosion of various acid-base media (such as acid mist and spills commonly encountered in experiments). Additionally, they have a uniform color (facilitating the observation of whether there is reagent residue) and impact resistance (preventing damage caused by the collision of experimental instruments).
• Typical Cases: Chemical laboratories in universities (floors of inorganic chemistry experimental benches) and quality inspection institutions (acid corrosion test platforms for materials).

5. Other Special Applications

• Civil Scenarios: Acid-resistant bricks are used for exterior walls of buildings in some areas with acidic soil (to prevent acidic substances in the soil from seeping and corroding the wall) and swimming pools (tiles in contact with acidic disinfectants, requiring both chlorine resistance and acid resistance).
• High-Temperature Application: Special acid-resistant bricks are used in glass factories (around molten glass pools, requiring both acid resistance and high-temperature resistance) and power plants (linings of flues in desulfurization and denitrification systems, featuring acid resistance and resistance to flue gas scouring).

III. Precautions for the Use of Acid-Resistant Bricks

• Medium: Ordinary silica acid-resistant bricks are not resistant to hydrofluoric acid (HF) or hot phosphoric acid (＞150℃). It is necessary to select the corresponding material according to the specific acidic medium (zircon sand acid-resistant bricks are resistant to hydrofluoric acid).
• Construction: When laying acid-resistant bricks, acid-resistant mortar must be used (such as epoxy acid-resistant mortar and water glass mortar). The use of ordinary cement should be avoided, as the alkaline components in cement will be corroded by acid, leading to brick detachment.
• Maintenance: If there is residual acidic medium on the surface of acid-resistant bricks, it should be rinsed with clean water in a timely manner (to avoid intensified corrosion caused by long-term accumulation). Impact from sharp objects should be prevented (to avoid brick cracking and loss of anti-corrosion effect).