COMPARISON OF REDUCING SUGARS AS AGENT TO RETARD CORROSION RATES

Abstract

This study reports the effect of adding sugars to prevent the corrosion of reinforcing bars. Various types of sugars, including reducing sugar aldose (sugar with an aldehyde group), ketose (sugar with a ketone group), and syrup with an expiration date, were used in experiments. These sugars exhibit remarkably similar skeletal structures and identical hydroxyl groups and hydrogen positions at carbon numbers 4–6. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Tafel extrapolation were performed to reveal the effects of the sugars and their reductive abilities. ICP-AES showed that the concentration of dissolved iron in the fructose solution was about 1/270 of that observed in the blank, the lowest concentration of dissolved iron in this experiment, followed by waste syrup (WS). This demonstrated the reducibility of rebar by sugars. The ICP-AES results are consistent with the experimental results obtained using Fehling's solution and Benedict's reagent, as reported in a previous study conducted in 2021. The results of Tafel extrapolation showed no significant differences in corrosion rate. However, the current measurement methods are not optimal. Furthermore, molecular orbital calculations performed to evaluate the binding energies of the transition states of sugars to enediol structures confirmed that ketose was more reductive than aldose.