Corrosion Resistance of Alumina Ceramic Lining Bricks
Alumina ceramic lining bricks possess excellent corrosion resistance with extremely strong chemical stability, and can maintain good corrosion resistance in most acid, alkali, salt media and chemical corrosion environments. However, their corrosion resistance effect varies with the alumina content, medium type and service temperature, with specific performances as follows:
Corrosion Resistance to Acid Media
Alumina ceramic lining bricks have good corrosion resistance to non-oxidizing acids (such as hydrochloric acid, dilute sulfuric acid, phosphoric acid) at room temperature, and almost no chemical reaction occurs. But in high-temperature or concentrated oxidizing acid environments (such as concentrated sulfuric acid, concentrated nitric acid, aqua regia), their surface will be corroded slowly, especially for lining bricks with alumina content lower than 95%, the corrosion rate will accelerate. For example, in dilute hydrochloric acid at room temperature, the corrosion rate of 99% alumina ceramics is less than 0.01mm/year, while in concentrated sulfuric acid at 100℃, the corrosion rate rises to 0.1-0.5mm/year.
Corrosion Resistance to Alkaline Media
Alumina ceramics have good stability in weak alkalis at room temperature (such as dilute sodium hydroxide solution, ammonia water), but in high-temperature and strong alkali environments (such as molten sodium hydroxide, concentrated potassium hydroxide solution), alumina will react chemically with alkalis to form aluminate, leading to gradual erosion of the lining brick surface. Therefore, alumina ceramic lining bricks should be used cautiously in working conditions with strong alkali and high temperature, or more alkali-resistant materials such as silicon carbide ceramics should be selected.
Corrosion Resistance to Salt Media
For common salt solutions (such as sodium chloride, calcium chloride, magnesium sulfate, etc.), alumina ceramic lining bricks can fully resist them at both room temperature and medium-low temperature (≤100℃), without problems such as dissolution, oxidation or electrochemical corrosion. This is also an important reason for their wide application in salt spray or salt solution working conditions in mining, chemical and other industries.
Influence of Alumina Content on Corrosion Resistance
The higher the alumina content, the stronger the compactness and chemical stability of the ceramic, and the better the corrosion resistance. 92% alumina ceramic lining bricks can meet the requirements of conventional weak acid, weak alkali and salt working conditions; 95%-99% alumina ceramic lining bricks can cope with more severe corrosion environments, such as higher concentration acid and salt media; high-purity alumina ceramics with more than 99.5% alumina can even be used for a short time in some high-temperature acid working conditions.
