7B04鋁合金在模擬海洋大氣環境下的腐蝕行為

7B04鋁合金在模擬海洋大氣環境下的腐蝕行為Corrosion Behavior of 7B04 Al-alloy in Simulated Marine Atmospheric Environment

海洋大氣環境下鋁合金的腐蝕本質上是薄液膜下的電化學腐蝕，與本體溶液中的腐蝕有很大不同，腐蝕速率與薄液膜的厚度及成分有關。建立并實驗驗證了薄液膜厚度、大氣相對濕度和鋁合金表面鹽沉積量3者之間的關系，研究7B04鋁合金在不同厚度和不同NaCl濃度薄液膜下的電化學性能。結果表明，薄液膜下7B04鋁合金的自然腐蝕電位較本體溶液中更容易達到穩定，且電位更正，自然腐蝕速率更大；液膜厚度減小，7B04鋁合金陰極極化電流密度增加，陽極反應受到抑制；薄液膜中NaCl濃度升高，7B04鋁合金的自然腐蝕電位降低，腐蝕速率上升，而陰陽極極化過程受NaCl濃度變化影響不大，當NaCl質量分數達到5%后，自然腐蝕電位基本不再變化。The corrosion of aluminum alloy in marine atmospheric environment was an essential electrochemical corrosion under thin electrolyte film, which was different from the corrosion in bulk solution, the corrosion rate was related to the thickness and composition of thin electrolyte film. The relationship among film thickness, relative humidity and salt deposit on aluminum alloy surface was established and verified by experiment. The electrochemical properties of 7B04 Al-alloy under thin electrolyte film with different thickness and different NaCl concentration were studied. The results indicate that the free-corrosion potential of 7B04 Al-alloy under thin electrolyte film is easier to reach steady state than that in bulk solution, both free-corrosion potential and corrosion rate are higher under thin electrolyte film. With the decrease of film thickness, the cathodic polarization current density of 7B04 Al-alloy increases, and the anode reaction is suppressed. With the increase of NaCl concentration in thin electrolyte film, the free-corrosion potential of 7B04 Al-alloy decreases, and the corrosion rate increases, but the polarization of the anode and cathode have little effect on the change of NaCl concentration. The free-corrosion potential of 7B04 Al-alloy is no longer changed when the mass fraction of NaCl reaches 5%.