SURFACE CHARACTERIZATION OF REINFORCING STEEL AND THE INTERACTION OF STEEL WITH INHIBITORS IN PORE SOLUTION

Studies of rebar surfaces following cleaning in various ways and following exposure to corrosive solutions in the presence and absence of inhibitors have been carried out using the surface-sensitive technique: x-ray photoelectron spectroscopy (XPS). After cleaning in hexane, rebar specimens were exposed to simulated pore solution with or without corrosion inhibitors under specified conditions. Subsequent XPS analysis of the rebar specimens indicated that the corrosion inhibitors sodium nitrite, sodium molybdate, sodium dihydrogen phosphate, sodium monofluorophoshate, and sodium tetraborate produced changes in rebar surface chemistry that could be associated with corrosion inhibition. The principal changes were (a) alteration in surface iron content, (b) reduction in the surface hydroxide concentration, and (c) increase in surface oxide oxygen concentration. The results are interpreted to indicate that these inhibitors promote the formation of surface oxides at the expense of hydroxide functionality. Results from the study of sodium tetraborate reveal that this inhibitor produces a coating on the rebar surface.