| 摘要: | 鋁－676鋅－l76鋅 (鋁6鋅l鎂) 合金經過適當的熱機處理，可獲得優良的機械性能，但其耐蝕性能却因第二相的析出幾乎傷失殆盡。因此本研究以電化學的技術來衡量鋁6鋅l鎂合金在氯鹽水溶液中之安定性；其中包括腐蝕電位 (Ea) 、孔蝕電位 (Eb) 及孔蝕保護電位 (Epp) 的測量，由所得之陽極極化曲線上發現鋁6鋅l鎂之ER恆處於Eb與Epp之間，且ΔE (=Eb-Ea) 決定於Cl-濃度、溫度及熱處理狀態；例如Eb分別為Cl-濃度及溫度的函數如下： 1. T=42℃; Eb=-62 Log [Cl-]-847 mv (vs. SCE) 2. [Cl-]=3%NaCl; Eb=-0.95 T(℃) -901 mv (vs. SCE) 鋁6鋅l鎂的孔蝕電位較諸其它商用鋁合金的為活潑，熱機處理非但未能影響上述三項特徵電位之排列順序；即Eb>Ea>Epp，反而能使Eb愈為接近ER，因此誘發鋁6鋅l鎂鈍態膜之局部破壞，結果導致高強度之孔蝕。
Although superior mechanical properties can be achieved through appropriate thermo mechanical treatments, the corrosion resistance of Al-6%Zn-1%Mg (Al6Zn1Mg) will however deteriorate drastically on account of the precipitation of second phase. Electrochemical techniques were employed in this study to evaluate the stability of Al6Zn1Mg in the presence of chloride solutions, among which the corrosion potential (ER), pitting potential (Eb) and protection potential (Epp) were determined by means of anodic polarizations. The results show that ED is always situated between Eb and EPP, and ΔE (=Eb-ER) strongly depends on Cl concentrations, temperature's and heat treatments. For example, Eb can be expressed as a function of CI concentration and temperature, respectively, as follows: 1. T=42℃; Eb=-62 Log [Cl-]-847 mv (vs. SCE) 2. [Cl-]=3%NaCl; Eb=-0.95 T(℃) -901 mv (vs. SCE) The pitting potential of Al6Zn1Mg is more active than those of other commercial aluminum alloys and thermo mechanical treatment has no significant influence on the sequence of potentials such as Eb > ER > Epp. Moreover, as Eb approaches ER, the passivity of Al6Zn1Mg tends to break down and thus leads to high intensity of pitting corrosion. |
