Study On Electrochemical Performance Of Zn-Al Alloy Sacrificial Anode Material In Reinforced Concrete Structure

Cathodic protection technology is one of the effective ways to solve the corrosion of steel bars in concrete structures under the environment of chloride salt erosion.At present,zinc and zinc alloy anode materials are the most widely used cathodic protection materials in reinforced concrete structures due to their higher current efficiency.However,the zinc alloy anode material itself contains impurity elements such as Fe,Cu,and Pb,which seriously affects the electrochemical performance of the zinc anode material such as solubility,current efficiency,and the like.How to effectively reduce the influence of heterogeneous elements,and improve the corrosion solubility and electrochemical performance of anode materials are hot topics of current research.In addition,the performance of the cathodic protection material is not only related to the material itself,but also affected by the application environment.The improvement of the application environment is conducive to increasing the activation degree of the zinc alloy anode and improving its protection to the reinforcing steel.Therefore,this article takes Zn-Al alloy anode as the research object,and uses alloying modification method to study the effect of rare earth?0.3La,0.7Ce?content on the corrosion solubility and electrochemical performance of Zn-Al alloy anode.Of Al-RE?RE?alloy for alkali activation research to prepare highly alkaline prefabricated mortar anode and evaluate its effectiveness under chloride salt erosion environment.The main research results are as follows:?1?For the alloying modification of Zn-Al alloy anodes by rare earth?La,Ce?,metallographic microscope,X-ray fluorescence?XRF?,scanning electron microscope?SEM?,energy spectrum?EDS?and X-ray diffraction?XRD?analysis,combined with constant current corrosion test,polarization curve test and electrochemical impedance test,etc.,studied the effects of different rare earth contents on the electrochem ical performance and corrosion resistance of Zn-Al alloy anode materials.The research results show that the addition of rare earth elements?La,Ce?significantly refines the structure of the Zn-Al alloy anode,improves the surface dissolution morphology of the Zn-Al alloy anode,improves the current efficiency,and thus improves the electrochemical performance;With the increase of the rare earth content,the corrosion resistance of the Zn-Al anode increases first and then decreases.When the rare earth content is 0.6%,the electrochemical performance and corrosion resistance perform best.This is mainly because the addition of rare earth elements?La,Ce?has a significant refinement effect on the anode structure of Zn-Al alloys,and the surface corrosion product layer has active anticorrosive performance,which reduces the corrosion activity.?2?For alkali activation research of Zn-Al?RE?alloy anodes,cyclic voltammetry test,polarization curve test,and electrochemical impedance universal test were us ed to study Zn-Al?RE?alloys in different basicity?pH:12,13,14,>14?Corrosion solubility in LiOH solution,combined with the corrosion morphology?SEM?of Zn-Al?RE?alloy and XRD analysis of corrosion products show that the corrosion dissolution of Zn-Al?RE?alloy The property increases with the increase of the pH of the LiOH solution.When the pH is greater than 14,the solubility is the best.As the pH of the solution increases,the corrosion products on the anode surface of the Zn-Al?RE?alloy gradually change from ZnO and Zn?OH?₂ which are not easily dissolved.The transformation into easily soluble Li₆ZnO₄ improves the corrosion solubility of Zn-Al?RE?alloy anodes.The higher the basicity,the better the solubility.?3?Combined with the alloying modification of Zn-Al alloy anode and activation research under high alkaline environment,a prefabricated high-alkali mortar-wrapped anode was prepared,and the corrosion test was accelerated by salt solution immersion corrosion and electromigration.Steel bars were used in the salt solution.Potential"-780 mV?SCE?"validity criterion.In concrete,by analyzing the cathodic protection current,the self-corrosion potential of the steel bar(E_corr),the appearance of the steel bar,the microstructure of zinc alloy anode corrosion products Morphology and composition,evaluation of the effectiveness of the homemade zinc alloy anode.The results show that the potential of zinc alloy anode protection steel bar in salt solution meets the"-780mV?SCE?"validity criterion,and the protection is good;the self-corrosion potential(E_corr)of sacrificial anode protection steel bar in concrete is greater than-276mV,and the probability of steel corrosion Less than 50%,the protective current density of the zinc alloy anode is 1³?A·cm^-2,which meets the EN12696-2000 standard.Combined with the appearance of the reinforcing steel in the concrete,it shows that the homemade zinc alloy anode has better protection;Compared with the anode,the pH of the homemade zinc alloy anode wrapped mortar is lower,which affects the corrosion solubility,so its protection needs to be further improved.