(A) study on the synthesis of Ca- and Mg-doped mesoporous silicates and their application to nontoxic anti-corrosive pigments

Abstract

Calcium and magnesium cations were reported to show corrosion inhibiting properties and the compounds containing them can be included in protective coating. Ca-exchanged silica has been used as a nontoxic anti-corrosive pigment instead of toxic pigments formulated with lead or hexavalent chromium. If a paint film is under attack from a corrosive environment, the pigment will release calcium and silicate ions and they form a protective layer on the metal surface. In this study, Ca- and Mg-doped mesoporous silicates such as MCM-41, MCM-48, and SBA-15 were successfully synthesized and mesopore structures were confirmed by X-Ray diffraction and $N_2$ adsorption/desorption. The doped amount of calcium or magnesium was varied to evaluate the anti-corrosive performance, and the composition of the samples was analyzed by EDS analysis. Corrosion test and salt spray test were carried out to evaluate the corrosion inhibiting properties of the samples. Ca- and Mg-doped mesoporous materials showed better performance than Ca-exchanged silica because they leach more amount of calcium or magnesium than Ca-exchanged silica. Besides, Ca-doped samples were shown to leach more amount of ions than Mg-doped samples and these results are consistent with the corrosion test results. Ca- and Mg-doped mesoporous materials synthesized in this research were shown to have better performance than traditional Ca-exchanged silica pigment and it is confirmed that they can be applied as general industrial pigments.