engleski

Tartrate as corrosion inhibitor in concrete – a pitting corrosion inhibition and influence on properties of mortar

In an attempt to clarify the mechanism of inhibition activity of carboxylate compounds towards chloride induced corrosion of steel rebar in the concrete, the effect of tartrate on the pitting corrosion and electronic properties of iron oxide film was studied as well as the effect of tartrate on the properties of mortar. A comprehensive study consisted of both the evaluation of corrosion activity of tartrate in solution and in mortar samples and its effect on properties of mortar in fresh and hardened state. The ability of tartrate to inhibit steel corrosion was confirmed in the simulated concrete pore solution and in the reinforced mortar samples through the observed shift of the pitting initiation potentials towards more positive values. It was postulated that tartrate adsorbs on the surface of the passive film therefore changing the film properties and competing with chloride ions in the pitting initiation process by blocking the surface active sites. Electrochemical impedance spectroscopy revealed that the presence of tartrate enhances the charge transfer resistance and interfacial capacitance. ATR FTIR measurements confirmed presence of the adsorbed tartrate at the steel surface. Adsorption of tartrate affected the semiconductive properties of the passive film by lowering the defect concentration and reducing the negative effect of chloride ions. Mortar mixtures were prepared with varying concentrations of tartrate added as admixture. The properties of mortar in fresh state (density, porosity, workability, time of initial and final setting, and heat of hydration) and in hardened state (compressive strength and penetrability properties) were tested. The addition of tartrate increased the workability of the mixture and slowed the setting process, but increased the final compressive strength and penetrability resistance of the mortar. The study shows that tartrate, when used as corrosion inhibitor in concrete, besides inhibiting properties has positive effects on mortar properties as well.

inhibitor; pitting; concrete

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