pH值對2024-T351鋁合金在NaCl溶液中電化學(xué)行為的影響

Effect of pH on Electrochemical Behavior of 2024-T351 Aluminium Alloy in NaCl Solution

采用動電位極化技術(shù)結(jié)合電化學(xué)阻抗譜測量, 研究了pH值對2024-T351鋁合金在0.6 mol·L-1 NaCl溶液中腐蝕電化學(xué)特性的影響規(guī)律。結(jié)果表明, 在pH=5～7的NaCl溶液中, 鋁合金表面可生成穩(wěn)定的氧化膜, 阻抗譜出現(xiàn)兩個容抗弧。隨著溶液pH的降低, 極化曲線上的陰極電流密度逐漸增加, 且氧化膜厚度減薄, 膜電阻和電荷轉(zhuǎn)移電阻均有所降低, 這表明, 氧化膜的保護(hù)性能隨pH的減小而降低。在酸性(pH=3)NaCl溶液中, 阻抗譜變?yōu)橐粋€容抗弧, 說明鋁合金表面的氧化膜難以穩(wěn)定存在, 基體合金直接與溶液接觸, 極化曲線表現(xiàn)出基體合金的電化學(xué)特性。
Potentiodynamic polarization test and electrochemical impedance spectroscopy(EIS) were applied to investigate the effect of pH on the electrochemical behavior of 2024-T351 aluminium alloy in 0.6 mol·L-1 NaCl solution. The results showed that the passive film on the surface of aluminium alloy was stable in NaCl solition when pH=5~7 and the Nyquist plots were characterized by two distinct capacitance arcs. With the decrease of pH, the cathodic current density increased, the passive film became thinner, both Rox and Rct decreased. In acid (pH=3) NaCl solution, there was only one capacitance arc in Nyquist plot, indicating that the passive film was not stable with the decrease of pH. As a result, the matrix alloy was exposed to solution directly and subject to corrosion, and the polarization curves showed the electrochemical characteristics of 2024-T351 aluminium alloy.

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