Effect Of Dynamic Recrystallization On Electrochemical Behavior Of Aluminum Alloy And Specific Adsorption Of Inhibitor

Friction stir welding (FSW) was a revolutionary jointing technology after the laser welding. During the FSW process, the material undergoes intense plastic deformation, and this dynamic recrystallization process would influence the inhibitor adsorption performance for aluminium alloy. So this thesis mainly focused on the interaction between the inhibitor and the FSWed weld in the ambient aqueous solution.Firstly, by gravimetric test, potentiodynamic polarization(PDP) curve test, electrochemical impedance spectra (EIS) and scanning electron microscope (SEM) observation, in the ambient acidic aqueous solution, the electrochemical behavior of 5083 parent metal and friction stir welding weld were comparatively investigated. Then with the adding sodium molybdate as inhibitor in the corrosive medium, by increasing the concentration or adsorption time of inhibitor, the effect of dynamic recrystallization after the welding on the specific adsorption of sodium molybdate was studied. The interaction mechanism bwteen the corrosion inhibitor and weld was preliminarily discussed.The Results showed that:in the blank corrosion medium of 0.2 M NaHSO3 and 0.6 M NaCl at room temperature, compared with 5083 parent metal, the corrosion potential Ecorr of FSW weld was more positive, the corrosion current density Icorr and average corrosion rate was less, but polarization resistance Rp increased. The morphology of FSW weld after ambient temperature static immersion test was relatively uniform, but for 5083, the morphology was relatively rough because of serious pitting.After adding sodium molybdate as inhibitor in the acidic corrosive medium, by increased the concentration or adsorption time of inhibitor, the average corrosion rate decreased, and inhibition efficiency increased; the Ecorr was more positive and Icorr was less, but polarization resistance Rp and charge transfer resistance Rct increased, interface capacitance Cc and double electric layer capacitance Cdl decreased. When testing temperature was given at 30℃, the minimum average corrosion rate and maximum inhibition efficiency were obtained.At the same test conditions (inhibitor concentration, test temperature, adsorption time), compared with 5083 parent metal, the Ecorr of FSW weld was more positive and Icorr was less, but polarization resistance Rp and charge transfer resistance Rct increased, interface capacitance Cc and double electric layer capacitance Cdi decreased. These results indicated that:during the FSW processing, the slightly elongated and larger grain structure in 5083 parent metal was significantly recrystallized and gradually produced the refined and equiaxed grains, which made specific adsorption ability on surface of FSW weld better than that of 5083 parent metal.