Study of chloride corrosion organic inhibitors in alkaline pore solution

This paper compares the inhibition properties of aspartic and lactic acid salts with nitrite ions and their effect on critical chloride concentration. The tests were carried out on carbon steel specimens in saturated lime solutions with pH adjusted in the range 13 to 13.6. The critical chloride concentrations were estimated through multiple specimen potentiostatic tests at potentials in the usual range for passive rebar in alkaline concrete of atmospheric structures. During tests, chloride salt was added every 48h until all specimens showed localized attacks, obtaining cumulative distribution curves, i.e. the fraction of corroded specimens as a function of the chlorides concentration. Furthermore, IR spectra were recorded for evaluating the presence of the organic inhibitors on the passivity film. The results confirm an inhibiting effect of 0.1M aspartate comparable with nitrite ions, at same concentration. The calcium l actate does not increase critical chloride concentration. However, the formation of a massive scale was observed, containing such substance that could reduce the corrosion propagation.