Identifying and understanding the inhibition mechanisms and performance of two organic concrete reinforcement corrosion inhibitor

The concrete reinforcement corrosion inhibition performance of two commercial organic inhibitors (MCI2005 and MCI2020) has been investigated in a practical marine application. Findings from this investigation have shown that the performance of the inhibitors was dependant on numerous factors including inhibitor concentration, the chloride content of the concrete, the location of the concrete relative to the tide level and the type of inhibitor used. In an attempt to better understand these findings from the field applications a detailed investigation of the inhibitor's fundamental properties was conducted. Experimental procedures were conducted in saturated Ca(OH)2 solution to simulate the high pH concrete environment. Electrochemical techniques such as Potentiodynamic Scans (PDS) and Cyclic Voltammetery (CV) were used to investigate protection mechanisms and surface interactions, as well as to quantify the effect of inhibitor concentration on performance. MCI2005 and MCI2020 were both shown to effectively inhibit chloride-induced corrosion at significant concentrations and exposure times. However, their inhibition mechanisms were shown to be different. MCI2005 functioned primarily as a cathodic inhibitor suppressing corrosion initiation, while MCI2020 was shown to behave more as a mixed inhibitor able to slow the propagation of existing corrosion. Using Fourier Transform Infra Red (FTIR) analysis and Scanning Electron Microscopy (SEM) the chemical interactions at the steel surface most likely responsible for the differing behaviour of the products were identified.