Corrosion Electrochemical Behavior Of Aircraft Aluminum Alloy Under Thin Electrolyte Layers Of Potassium Acetate Deicing Fluid

Thin electrolyte layer corrosion test device and test method were established in the laboratory,which are consistent with the actual use conditions of aircraft deicing liquids.The corrosion conditions of potassium acetate deicing fluid to aircraft aluminum thin electrolyte layers in low temperature environments were simulated.Potentiodynamic polarization(PD)measurements,electrochemical impedance spectroscopy(EIS)measurements and electrochemical active point of micro-area Scanning Vibrating Electrode Technique(SVET)were conducted on 2024 aluminum alloy and anodized aluminum alloy for aircraft under thin electrolyte layers of potassium acetate deicing fluid.The corrosion electrochemical behaviors of the two materials under different thin electrolyte layer thicknesses and different immersion conditions were studied and the effects of different deicing fluid concentrations on the corrosion electrochemical behaviors of the two materials were compared.The results show that the corrosion rate of 2024 aluminum alloy and anodized aluminum alloy for aircraft first increased and then decreased with decreasing thickness of the thin electrolyte layers,and reached a maximum value when the thickness of the liquid film was about 150μm.Under the condition of thin electrolyte layer,the corrosion process was mainly controlled by cathodic processes and oxygen diffusion.With the decrease in thin electrolyte layer thickness;the oxygen content in the solution increased,the resistance at cathode decreased,and the corrosion rate increased.When the thickness of the thin electrolyte layer was reduced to less than 150μm,making oxygen easy to reach the surface of aluminum alloy,a protective layer was formed on the surface that potentially reduced further attacks of the surface.The corrosion reaction process was gradually transformed into the anodic process control,and the corrosion rate was reduced.With increase in the concentration of the deicing solution;the concentration of the inhibitor in the deicing solution also increased(the inhibitor is a component of the deicing fluid),the corrosion efficiency increased,and the corrosion rate of 2024 aluminum alloy and anodized aluminum alloy decreased.Since the corrosion process of aircraft aluminum under thin electrolyte layer of deicing liquid is controlled by oxygen concentration polarization and activation polarization under the condition of full immersion,the corrosion rate of 2024 aluminum alloy and anodized aluminum alloy under full immersion and thin electrolyte layers varies greatly with the concentration of deicing liquid.In the same deicing solution,the corrosion rate of 2024 aluminum alloy and anodized aluminum alloy under thin electrolyte layers is higher than that under full immersion.In natural state,the area of micro cathode and micro anode of aluminum alloy under thin electrolyte layers of deicing solution at various concentrations was the same,and they were randomly and uniformly distributed on the sample surface.From the average potential,the corrosion tendency of aluminum alloy initially increased and then decreased with increasing concentration.From the corrosion current density,the corrosion rate increased with increasing deicing solution concentration.Under polarization,there were large cathodes and small anodes on the surface of the anodized aluminum alloy,and the anode was evenly distributed on the surface of the sample,which shows that through polarization,the anodized aluminum alloy under thin electrolyte layer forms a passive film.