Role of Carbon Dioxide on the Corrosion of Carbon Steel Reinforcing Bar in Simulating Concrete Electrolyte

Abdulkareem M.A Al-Sammarraie

doi:10.21123/bsj.2020.17.1.0093

Abstract

The main factors that make it possible to get the corrosion of reinforcing steel in concrete are chloride ions and the absorption of carbon dioxide from the environment, and each of them works with a mechanism which destroys the stable immunity of rebar in the concrete. In this work the effect of carbon dioxide content in the artificial concrete solution on the corrosion behavior of carbon steel reinforcing bar (CSRB) was studied, potentiostatically using CO2 stream gas at 6 level of concentrations; 0.03 to 2.0 weight percent, and the effect of rising electrolyte temperature was also followed in the range 20 to 50ᴼ C. Tafel plots and cyclic polarization procedures were obeyed to investigate the corrosion parameters and pitting susceptibility respectively. The change in the microstructure and morphology of the CSRB after polarization in the simulate concrete solution was studied using optical and atomic force microscopes. The results show that the corrosion rate of the CSRB in artificial concrete greatly increases with the existence of CO2 gas and highly depends on its concentration in the range 0.03 to 2.0% .No sign for pitting corrosion is recorded at all CO2 concentrations and the general corrosion is the main problem in the conditions under consideration.

Highlights

Concrete structures such as bridges, reservoirs, and residential buildings are designed to last for decades, and their collapse is mainly due to the corrosion of the used reinforcing carbon steel [1,2,3], the basic environment of the concrete structure provides self-protection by producing a very thin passive film which limits the metal loss from the carbon steel surface [4,5]
The steel rebar was immersed in three electrode cells and served as working electrode, the Pt-electrode served as counter electrode, and Ag/AgCl as references electrode, the CO2 gas was introduced to the corrosion cell through porcelain bubblier from CO2 gas cylinder(BOC, UK), Fig.[2]
The open circuit potential (OCP) was measured using Potentiostat (Mlab200, Bank Elektronik Intelligent control, Germany) and the carbon steel reinforcing bar (CSRB) was polarized in the simulate concrete solution (Ca(OH)2 (2gm), KOH (22.44mg), NaOH (8mg) in 1L of distill water) after passing the required concentration of CO2 gas (0.03, 0.26, 0.50, 1.00, 1.50, and 2.00%)

Summary

Introduction

Concrete structures such as bridges, reservoirs, and residential buildings are designed to last for decades, and their collapse is mainly due to the corrosion of the used reinforcing carbon steel [1,2,3], the basic environment of the concrete structure provides self-protection by producing a very thin passive film which limits the metal loss from the carbon steel surface [4,5]. Several studies have shown that the main cause of the destruction of the protective passive layer of carbon steel in concrete is chloride ions, carbon dioxide and other atmospheric pollutants and will corrode faster [6,7,8,9,10]. This work focuses on examining the effect of increasing the concentration of carbon dioxide on the rate of corrosion of steel rebar. It depends on temperature, and the probability of pitting corrosion

Materials and Methods

Results and Discussion

Conclusions