Ceramics-Silikáty

Glass flakes are an important filler in coatings for protecting metallic substrates or equipment from corrosion. Theoretically, Al₂O₃ can increase the performance of Na₂O-CaO-SiO₂ glass flakes, but also increase both energy consumption and difficulty in the production of glass flakes. In the literature, there is a lack of detailed experimental studies directly showing the influence of Al₂O₃ content on the glass flake products. Herein, the structure and the chemical durability of two glass flakes A and B with 0.67 wt% and 3.08 wt% of Al₂O₃ and different specific surface areas were investigated and compared in detail. According to the ²⁹Si NMR and FTIR results, both flakes have the same polymerization degree of silica tetrahedra. However, the flakes B have increased structural symmetry by 7.04%. And the resistance of the flakes B toward HCl, H₂SO₄, HNO₃ solutions and water increased by 13.6%, 29.0 %, 28.3% and 35.6% than that of flakes A, respectively. The results showed that the increase of specific surface area by 0.1 m2/g, the weight losses of glass flakes A and B in HCl solutions increased by 44.25% and 25.53% respectively. Thus, the chemical durability of flakes B is slightly less affected by specific surface area, suggesting the possibility to gain similar chemical durability of glass flakes by either tuning the particle size or increase the Al₂O₃ content. FTIR spectral and SEM analysis revealed that the water and acid corrosion altered not only the surface morphology, but also the silanol state as well as the Si-O-Si bonds in [SiO₄] of the flakes. This study provided detailed data about the influence of Al₂O₃ content on the structure, water and acid resistance of glass flake products, providing useful reference for manufacturers to design glass flakes with good balance between production and properties.