Comparative study of three sodium phosphates as corrosion inhibitors for steel reinforcements

摘要

A comparative study was performed on the inhibition of steel reinforcement corrosion using three soluble phosphates: sodium monofluorophosphate (Na_2PO_3F), disodium hydrogen phosphate (Na_2HPO_4) and trisodium phosphate (Na_3PO_4). Tests were carried out using ordinary Portland cement (OPC) paste specimens and OPC mortar specimens with embedded steel reinforcements. The corrosion inhibitors were deployed in two different ways: by immersion of OPC specimens in aqueous solutions containing the soluble phosphates (migrating corrosion inhibitor), and by addition of the phosphate powders to a fresh OPC paste (admixture corrosion inhibitor). After curing, the tested specimens were studied using X-ray diffraction, wavelength-dispersive electron microprobe analysis, linear polarisation resistance and electrochemical corrosion potential. A correlation was found between the phosphate content (by migration or admixture) in the OPC matrices and the steel corrosion rate.