Assessment of corrosion inhibition efficiency of generic compounds having different functional groups in carbonated pore solution with chlorides and migration ability in concrete

Abstract

In the present study, corrosion inhibition effect of generic compounds in simulated carbonated pore solution contaminated by chloride ions (Cl-) was investigated. The performance of two generic compounds, namely Triethylphosphate (TEP) and Salicyaldehyde (SA) at varying concentrations was investigated by electrochemical measurement technique (potentiodynamic polarization curves), optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The test results in simulated pore solution show that both TEP and SA reduced the corrosion rate irrespective to the tested concentration levels. It is found that efficiency of TEP increases from 65.36% to 83.18% with increase in concentration from 0.05 M to 0.2 M; while efficiency of SA was as high as 96.4% even at 0.05 M concentration. Surface analysis data confirms that corrosion product on specimen immersed in contaminated environment contains FeOOH, Fe2O3 and Fe3O4, while presence of phosphate group in TEP able reduce the formation of corrosion product. SEM and EDS data shows the formation of protective layer on specimen immersed in SA admixed solution that contains higher C and O content. The spectra band obtain by FTIR confirms the adsorption of SA through the interaction of CHO and phenolate ion with metal surface. The mechanism of inhibition revolves around the type of heteroatom present within the molecular structure. While TEP retarded the corrosion of rebar by advancing the iron oxide film growth and healing the defects present in the protective film; SA formed an adsorptive black layer over the exposed surface by chelation process. Out of the two compounds, the inhibition efficiency of SA was as high as 99%.The best performing compound was further applied on the concrete surface to check its migration ability through the cover concrete. The percolation ability was determined by using thin layer chromatography (TLC) and ultraviolet–visible spectroscopy (UV–Vis). The tests conducted on the powdered samples collected from various depths at different time intervals confirmed the percolation potential of the generic compound. Overall, it can be concluded that SA has the potential to act as migratory inhibitor to retard rebar corrosion in the dual corrosive environment of chlorides and carbonation.