Chemical and electrochemical properties of potassium silicate coating enhanced by calcium hydrogen phosphate

• CaHPO 4 ·2H 2 O can improve the electrochemical properties of the silicate coatings. • With CaHPO 4 ·2H 2 O, the polymerization of the silicate coatings increases from Q 2 to Q 3 . • At 230 °C, addition of curing agent can prohibit the CO 2 curing effect. Potassium silicate coatings cured by calcium hydrogen phosphate (CaHPO 4 ∙2H 2 O) were prepared at ambient and elevated curing temperatures. Microstructures, chemical and electrochemical properties of the coatings were investigated using XRD, SEM, FTIR and EIS, respectively. CaHPO 4 ∙2H 2 O powders declined basicity of potassium silicate solution and degraded into Ca 3 (PO) 4 during curing. Two major effects on chemistry were revealed: 1) increasing polymerization of the silicate coatings from Q 2 to Q 3 ; 2) prohibiting the CO 2 curing effect. Thus, addition of CaHPO 4 ∙2H 2 O into silicate solutions can effectively improve electrochemical properties of the coatings.