Effect Of Stress On Corrosion Behavior Of Copper-aluminum Composite Plates Under Salt Spray Corrosion Condition

Cu-Al laminated composite material is mainly used to replace pure copper,solve the problem of expensive copper resources,and has been applied in conduction,heat dissipation,decoration and other fields.However,due to the formation of dissimilar metal links on the Cu-Al laminated composite material structure,the galvanic phenomenon will occur during corrosion,showing a different corrosion mechanism from pure copper and aluminum,which will have an impact on the use of such materials performance changes.Especially,the corrosion mechanism of Cu-Al laminated composite material becomes more complex under the corrosive environment and the action of external forces.Researches show that salt spray corrosion experiment was used to construct corrosion environment,and different stresses were applied to simulate the working conditions of Cu-Al laminated composite material,the surface corrosion morphology of Cu-Al composite plates under different stress conditions was analyzed by SEM,and the surface corrosion products were analyzed by EDS scanning,X-ray diffractometer analysis of corrosion product phase composition,and the polarization curve and electrochemical impedance spectroscopy(EIS)of salt spray corroded samples were measured by using the three-electrode system of VSP-300electrochemical workstation,The effects of tensile stress?compressive stress and bending deformation on corrosion behavior were studied,and the corrosion mechanism was analyzed.The results show that the corrosion behavior of Cu-Al composite plates were promoted by tensile stress under the condition of accelerated corrosion by salt spray.When no tensile stress was applied,corrosion pits appear only on the interface of Cu-Al composite plates with small diameter,but not on the side of Al composite plates with obvious corrosion.Under the action of tensile stress,corrosion occurs on the interface of Cu-Al composite plates with large diameter and deep corrosion pits,while pitting corrosion occurs on the side of Al and extends along the direction of tensile stress.However,the corrosion behavior of Cu-Al composite plates were restrained by the application of compressive stress.When no stress was applied in the process of the experiment,the corrosion pattern at the interface of Cu-Al-Cu composite plates were crack,when the applied compressive stress level reached 20%of the material yield strength,the corrosion inhibition of the material was the most obvious,and the corrosion form was pitting pit.But with the increase of compressive stress,the inhibition effect was weakened.Different bending deformations were applied to the Cu-Al composite plates,the Al side of the Cu-Al composite plates were stretched out and the Cu-Al interface was extruded,both the interface and the Al matrix were corroded,and corrosion tunnels and corrosion pits appeared at the interface.The Cu side was stretched at the Cu-Al interface of the external bending Cu-Al composite plates,while the Al side was squeezed.At this time,the corrosion occurs mainly at the interface of the Cu-Al composite plates,and the corrosion morphology at the interface mainly exists in the form of obvious elliptical corrosion pits.When the bending angle of Al side was 30°,the capacitive reactance arc and corrosion resistance of the Cu-Al composite plates were the highest.The bending angle of Cu-Al composite plates with Cu side outside bending was 120°,the capacitive reactance arc was the biggest and the corrosion resistance was the best.By comparing the polarization resistance of the angle with the best corrosion resistance,the former was 19860?·cm²,the latter was 18260?·cm²,in comparison,Cu-Al composite plates with Al side bent outside have better corrosion resistance.Al₂O₃,Al(OH)₃,Al O(OH)were the corrosion products of Cu-Al composite plates under different stresses.