Sequential co-precipitation as a convenient preparation method o anticorrosive hybrid calcium phosphate/calcium silicate powder pigments

摘要

Hybrid powder pigments based on calcium phosphates and Ca-exchange silicates (CPS) were prepared via a sequential co-precipitation method. Chemical composition of CPS and reference pigments (calcium phosphates (CP) and calcium silicates (CS)) was investigated in relation to molar ratio of substrates and pH value of reaction medium. Steel corrosion inhibition efficiency (eta) for the pigments was evaluated using electrochemical noise (EN), polarization resistance (POL) and Tafel (TAF) techniques. XRD and FT-IR data indicated that CPS are mixtures of the relevant CP and CS pigments. The EN, POL and TAF data revealed a sinusoidal relation between eta and P:Si molar ratio in the substrates (at pH = 8.5 or 11). The best anticorrosive features were observed for CPS prepared at Si molar excess (pH = 8.5) (eta(EN) = 99%, eta(POL )= 73% and eta(TAF) = 85%). Probably, the synergistic effect was resulted by a specific content and molar ratio of Ca, P2O5 and Si in the CPS-based electrolytes. (C) 2020 Elsevier B.V. All rights reserved.