The Electrochemical Principle Of The Single Wire-electrode AC Probe And Its Applications In Some Corrosion Systems

To detect the electrochemical corrosion in some extreme environments,a single-wire electrode AC probe technology without a reference electrode and counter electrode was developed,which can effectively avoid the problems of poor stability and premature failure of commom traditional three-electrode electrochemical test systems.This new method uses a metallic wire-electrode.Through AC impedance measurement by applying a stimulating voltage of 5 mV in a frequency range of 105-1 Hz,the quantitative information,such as instantaneous corrosion rate,interface capacitance(RP,C)and cumulative damage(RM),of the corrosion system respresented by the single-wire electrode,could be obtained at the same time.The entire test process is less than 1 min.Through experimental validation and theoretical analysis,the impedance spectrum model of the single-wire electrode AC probe technology was established.The corrosion behavior of the single-wire electrode AC probe technology test was measured to be consistent with that in a traditional three-electrode electrochemical system.Thus,the developed new probe technique is accurate,reliable,fast and simple,and can find many applications in electrochemical corrosion monitoring.Through the single-wire AC probe technology,the corrosion behaviors of magnesium,zinc,carbon steel and stainless steel single-wire electrodes in 3.5 wt.%NaCl and artificial seawater were studied.In 3.5 wt.%NaCl solution,the average corrosion rate of these metal wires can be ranked as follows:carbon steel>zinc>stainless steel.The corrosion behaviors of different single-wire electrode in 3.5 wt.%NaCl were different.Their surface films could change with time,which was consistent with the inditcations by the measurements in the traditional three-electrode system.At a high temperature(95?)in the 3.5 wt.%NaCl solution,the probe could even be used to reliably measure instant and long-term corrosion information.The corrosion behaviors of several different metals in the alkaline environment of chlorine-containing concrete simulating liquid were studied by using the single wire electrode probe technique in 3.5 wt.%NaCl solution.It was found that the corrosion rate of aluminum and zinc wire greatly increased with time,while that of carbon steel slowed down.The corrosion behaviors and damage degrees of the wire electrodes made of different metals were different in the alkaline chlorine-containing concrete simulating liquid.Due to the amphoteric chemistry of aluminum and zinc,they could be converted into soluble AlO2-and ZnO22-and undergo rapid corrosion and serious damage,which can be much faster and serever than in neutral 3.5 wt.%NaCl,whereas the corrosion rates of the carbon steel and magnesium greatly slowed down with time.When the carbon steel wire was coupled with magnesium,aluminum and zinc wire respectively,the corrosion behaviors of the anode and cathode were different.In an alkaline concrete simulant solution,the magnesium is more sensitive to Cl-ions than zinc and aluminum.After contaiminated by Cl-,the corrosion of the anode magnesium wire became much more severe,while aluminum wire and zinc wire had similar corrosion rates,both higher than those in the concrete simulating solution.These experiments proved the feasibility of the single wire AC probe in concrete.