Addition of ceramics materials to improve the corrosion resistance of alumina refractories

This review shows that adding ceramic materials such as ZrO2, ZrSiO4, TiO2, SiO2, Cr2O3, etc., to abase alumina refractory clay, improves the corrosion resistance under the presence of acid (H2SO4, HCl, HNO3, etc) and/or alkaline (NaOH, KOH, Na2O, Ca(OH)(2), etc) solutions. Characterization techniques, such as SEM, XRD, ICP-MS analysis, and weight loss show individual or correlated properties between apparent porosity, bulk density, mass loss, total number of eluted ions from alumina refractories, and the degree of corrosion resistance obtained by sintering. Static and dynamic (ASTM C-874) slag cup tests are performed by immersion or exposure to a continuous flow stream in acid and/or alkaline solutions. Results show that adding 81.6 mol% Cr2O3, 4 mol% TiO2 to the Al2O3 base reduces corrosion damage depth by SiO2-CaO-Al2O3 molten oxide. Sintered mullite matrix increases its corrosion resistance against alkaline vapors by adding 16% of ZrSiO4 center dot SiO2-Al2O3 refractory ceramics with mixtures of 67-23, 56-38, 25-71%, respectively, have 98% resistance against acid solutions. However, their resistance to alkaline solutions is 58% with 23% alumina and rises up to 88% with 71% of alumina. It is concluded that higher content of corundum (alpha-Al2O3) and mullite phases on refractory ceramic improves its resistance to acid and alkaline solutions and that the attack of degrading solution is preferential over impurities in the phases present near the grain boundaries.