Efficacies of sodium nitrite and sodium citrate\u2013zinc acetate mixture to inhibit steel rebar corrosion in simulated concrete interstitial solution contaminated with NaCl

Joby Thomas Kakkassery,Vinod Raphael Palayoor,Binsi Paulson Maliekkal

doi:10.1007/s40090-018-0142-7

Joby Thomas Kakkassery, Vinod Raphael Palayoor + Show 1 more

Open Access

https://doi.org/10.1007/s40090-018-0142-7

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Abstract

Investigations were carried out to compare the effectiveness of compounds such as sodium nitrite, trisodium citrate (TSC) and TSC–zinc acetate to inhibit the corrosion of steel rebar in simulated concrete interstitial solution contaminated with chloride and to explain the mechanism of corrosion inhibition on reinforcing steel by these systems. Inhibition efficiency of these systems was studied by electrochemical techniques such as potentiodynamic polarization and half cell potential measurements. Electronic spectral studies of simulated pore solution and FT-IR spectral investigations of the film deposited on steel surface were carried out for understanding the mechanism of corrosion inhibition. Microscopic surface analysis was conducted to obtain the surface morphological behaviour of steel rebar. TSC alone was not exhibited good corrosion inhibition at very low and high concentrations according to electrochemical studies. However, in the presence of zinc acetate, corrosion protection efficiency of TSC increased appreciably. When comparing with sodium nitrite, TSC in the presence and absence of zinc acetate displayed good corrosion inhibition efficiency. Among a number of samples, TSC 100 ppm-zinc acetate 50 ppm combination showed maximum corrosion inhibition efficiency on steel rebar in simulated concrete interstitial solution.

Highlights

Premature deterioration of concrete structures mainly occurs due to the ingress of chloride ions and carbon dioxide [1]
Some authors argue that those compounds which are used to protect concrete reinforcement are not effective [10] when the concrete is kept immersed in NaCl solution, whereas others report that some compounds are effective in reducing corrosion rate of steel rebar in concrete contaminated with chlorides [22, 23]
It is understandable from the polarization data that at very low concentration (50 ppm), sodium nitrite acted as a corrosion antagonist, i.e., the corrosion rate of steel rebar treated with nitrite was greater than that of the rebar immersed in concrete pore solution (CPS) without nitrite

Summary

Introduction

Premature deterioration of concrete structures mainly occurs due to the ingress of chloride ions and carbon dioxide [1]. Some authors argue that those compounds which are used to protect concrete reinforcement are not effective [10] when the concrete is kept immersed in NaCl solution, whereas others report that some compounds are effective in reducing corrosion rate of steel rebar in concrete contaminated with chlorides [22, 23]. The present investigation aims to explain the behaviour of these chemical species on steel rebar in contaminated concrete pore solution. Chemicals such as trisodium citrate (98%), sodium chloride (> 99.9%), NaNO2 (EMSURE®) and zinc acetate (> 99%) were purchased from Merck Millipore. To investigate the surface morphological changes on the steel rod dipped in simulated concrete pore solution [46, 47], microscopic studies were performed using Leica Stereo Microscope (S8ACO)

Results and discussion

NaNO2 50ppm

Conclusions