氧化鋁強化鋁基複合材料在3.5%鹽水中之腐蝕特性

Corrosion Behavior of Al2O3 Reinforced Al Composite in 3.5% NaCl Solution

本文主要在探討溶於水中之氧對氧化鋁強化鋁基複合材料在3.5%鹽水中之腐蝕特性。實驗之進行乃採取簡單之3.5%鹽水浸泡試驗，測量開路電位之變化以及不同浸泡時間後的重量變化，表面孔蝕數量之定量金相。結果發現於溶氧的鹽水溶液中，複合材料的抗腐蝕性較鋁為差，孔蝕的情形亦較為嚴重，浸泡期間開路電位也較不穩定。於不含氧的水溶液中之情況，鋁及複合材料之腐蝕現象大為改善，兩者之腐蝕特徵相近。然而，在電化學極化之實驗中，複合材料依然顯現較差之抗腐蝕性。氧化鋁強化相在不含氧水溶液之環境中對腐蝕之行為並無影響，反而水溶液中的氧對複合材料之抗腐蝕性有很大之效應。

The main objective of this work is to study the effect of the dissolved oxygen on the corrosion behavior of Al2O3/Al composite in a 3.5% aqueous NaCl solution. The corrosion behaviors of the Al and its composite were evaluated by a simple immersion test for 3 weeks in 3.5% NaCl solution. The open circuit potentials of the Al and its composite were recorded continuously through the immersion duration with and without the purging of dissolved oxygen. After different periods of immersion, the weight losses, surface pitting and its amount and metallographs in the metal and composite were measured and examined quantitatively. The results show that the composite has less corrosion resistance when the solution contained dissolved oxygen, and the pitting was more severe than that in the corresponding control Al. The composite also exhibited an unstable open circuit potential during the immersion. In the absence of dissolved oxygen, pitting corrosion resistance of the composite and aluminum was largely improved, and both materials exhibited the same corrosion behavior. However, the electrochemical test result showed that the composite showed the less corrosion resistant behavior than that of the Al. The Al2O3 reinforcements apparently had no effect on the pitting behavior of the Al matrix if oxygen was absent in the solution. In summary, the dissolved oxygen exhibits a significant influence on the corrosion behavior of Al matrix than does the Al2O3 reinforcement.