Corrosion Behavior And Impressed Current Cathodic Protection Of Aluminum Alloy In3.5%Sodioum Chloride Solution

Aluminum alloy with excellent corrosion resistance, low density, high hardness,excellent physical and mechanical properties can be used as ideal marine engineeringmaterials.Since seawater is recognized to be very corrosive for metals，the oxide film breaksdown at specific points leading to the formation of pits on the aluminum surface. Therefore, itis neeessary to study the corrosion behaviors of aluminum alloy in chloride ion solution.Inthis paper，electrochemical polarization,electrochemical impedance spectroscopy (EIS) andelectrochemical techniques combined with seanning electron microscopy(SEM)，digitalmicroscope were used to study the corrosion behaviors of new Al-Mg aluminum alloysmaterial in static and flow state3.5%NaCl solution.The research results of this paper are asfollow：The corrosion behavior of Al-Mg aluminum alloy in static3.5%NaCl solution wasstudied. Electrochemical tests and Weight loss corrosion test were used to compare thecorrosion behavior in different immersion time. With the extension of immersion time,gradually serious corrosion, corrosion rate increases gradually, corrosion potential shiftednegatively, to a certain degree of corrosion corrosion potential tends to be stable. Inelectrochemical impedance spectroscopy there was the inductive reactance, capacitance loopdiameter increased. Corrosion products were characterized by means of SEM, Al-Mgaluminum alloys was mainly to point corrosion.The effect of pH on the corrosion behavior of Al-Mg aluminum alloy in static3.5%NaClsolution was studied. The corrosion potential of Al-Mg aluminum alloy shifted negatively, thepassivation current density increased and the passive potential range broadened,but the pittingcorrosion potential changed little with the increase of pH value. The result obtained fromelectrochemical impedance spectroscopy test indicated that capacitance arc diameterdeereased，the impedance modulus decreased with the increase of pH value, showing thefastest corrosion rate of aluminum alloy Al-Mg in alkaline3.5%NaCl solution. Warburgimpedance appeared at low frequency, and the cathode process was controlled by diffusion.By means of SEM found that, in addition to pitting corrosion occurred, but also because of thealkaline solution occurs intergranular corrosion, resulting in a uniform corrosion.The corrosion behavior of Al-Mg aluminum alloy in flow3.5%NaCl solution the corrosion behavior was studied. In early experiments, aluminum alloy corrosion currentdensity was higher, with the extension of immersion time, the corrosion potential shiftednegatively happened, the corrosion current density decreases. Description of the surface hasbeen completely corrosion, in a surface forming a thick oxide film, retard the corrosion rate.As the speed increased, the corrosion rate was relatively lower.Impressed cathodic current protection of Al-Mg aluminum alloy in3.5%NaCl solutionwas studied. Through different protection potentials in static and flow solution of aluminumalloy for cathode protection， in a static state-0.9~-0.95V played a very good protectiveeffect, the flow state of the1.0V near played a good protective effect. Through the SEM tocharacterize the samples characterization, revealed the emergence of intergranular corrosion,in imposing cathodic protection, intermetallic compound near the local pH value increase.