Localized Corrosion Inhibition of Carbon Steel in Carbonated Concrete Pore Solutions Using Wire Beam Electrodes

Abstract

The initiation,growth,and temporal and spatial distribution of localized corrosion of Q345B carbon steel in carbonated concrete pore solutions(pH 9.6) containing 0.1 mol·L-1 Cl-ions were investigated using a potential and galvanic mapping technique based on a wire beam electrode(WBE).Different mechanisms for repair and suppression on the stable localized corrosion by tetraethylenepentamine(TEPA) and nitrite were compared.The results indicate that nitrite can inhibit the active dissolution of steel beneath the rust layer because of the fast penetration of nitrite into the rust layer.However,TEPA can promote active dissolution under the rust layer initially because of its slow penetration rate through the rust layer.The localized active dissolution was only refrained after a long time because of TEPA molecules permeating into the interface between the rust layer and the steel matrix.Electrochemical impedance spectroscopy(EIS) was useful in allowing us to determine how the localized corrosion was initiated but failed to indicate the heterogeneous adsorption of the inhibitors on steel.A new localized corrosion factor(LF) based on galvanic mapping is proposed and is shown to be effective for the characterization of the localization of corrosion and the inhibition effect of inhibitors on localized corrosion.