Abstract
The inhibition properties of aspartic and lactic acid salts are compared with nitrite ions with regard to their effect on critical chloride concentration. The tests were carried out on carbon steel specimens in simulated pore solutions with initial pH in the range of 12.6 to 13.8. The critical chloride concentrations were estimated through multiple specimen potentiostatic tests at potentials in the usual range for passive rebar in noncarbonated concrete structures. During tests, chloride ions were progressively added until all specimens showed localized attack, obtaining cumulative distribution curves reporting the fraction of corroded specimens as a function of chloride concentration. The presence of the organic inhibitors on the passivity film was detected by IR spectra. The results confirm that 0.1 M aspartate exhibits an inhibiting effect comparable with nitrite ions of the same concentration. Calcium lactate does not increase critical chloride concentration; however it appears to promote the formation of a massive scale, reducing the corrosion propagation.
Highlights
The use of corrosion inhibitors as chemical admixtures during concrete mixing would be a simple and cost-effective solution for increasing concrete structures durability
This paper reports on multiple specimen potentiostatic tests comparing the inhibition properties of aspartate and lactate with nitrite ions
This paper studies the effect of the addition of lactic and aspartic acid salts on localized corrosion of passive rebars in alkaline simulated pore solution initiated by chloride ions
Summary
The use of corrosion inhibitors as chemical admixtures during concrete mixing would be a simple and cost-effective solution for increasing concrete structures durability. Tests in simulated concrete pore solutions are widely adopted for experimental study of chloride corrosion. This approach does not reproduce the metal/hydrated cement paste interface and its buffering capacity, which is significant in pitting initiation, as stressed by Page [8]. It allows cheap and rapid testing suitable for the screening of a large number of substances in a well-controlled environment. This paper reports on multiple specimen potentiostatic tests comparing the inhibition properties of aspartate and lactate with nitrite ions. The effect of pH and chloride concentration on the pitting initiation was evaluated
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