無電鍍鎳複合鍍層對AA7075鋁合金在3.5%NaCl水溶液中應力腐蝕破壞的影響

本研究藉由無電鍍法，在AA7075鋁合金原基材經表面陽極處理，沉積無電鍍Ni-P複合鍍層，分析鍍膜的結構與機械性質，並探討無電鍍Ni-P複合鍍層對AA7075鋁合金在3.5%NaCl水溶液中應力腐蝕破壞的影響。實驗中使用AA7075鋁合金原基材經陽極處理，封孔處理，無電鍍鎳磷，無電鍍Ni-P+TiO2複合鍍層，經慢應變速率拉伸(SSRT)在3.5%NaCl溶液中應力腐蝕破壞試驗。本實驗利用掃描式電子顯微鏡（SEM）及X光能量散射分析儀(SEM-EDS) 、維克氏微硬度試驗機(Hv)等，觀察鍍膜表面的形態、鍍層的元素成份分析、量測表面硬度。在3.5%NaCl水溶液中進行磨耗腐蝕試驗，並進行電化學動態極化法分析試驗。研究結果顯示AA7075鋁合金試片表面經陽極處理後硬度值增加，其無電鍍鎳磷複合鍍層能有效的增加鍍層表面晶粒均勻附著及硬度值。另外無電鍍Ni-P複合鍍層，經由適當的陽極處理將能有效提升沉積效率、光滑度、緻密性與附著性，因而對於AA7075鋁合金經陽極表面處理後在3.5%NaCl水溶液中之耐應力腐蝕破壞有顯著的改進效果。

關鍵字

應力腐蝕；慢應變速率拉伸試驗；無電鍍鎳磷複合鍍層；動態極化； AA7075 鋁合金

並列摘要

This study used electroless plating process to prepare Ni-P composite coating on AA7075 aluminum alloy surface after anodizing treatment. The Stress-Corrosion Cracking (SCC) charactenrstics for the coating in 3.5%NaCl aqueous solution via slow strain rate test was also studied. The surface morphology, element composition and surface hardness of the coatings were analyzed by SEM, EDS and Vicker’s hardness tester. The corrosion and wear-corrosion resistance of electrolessplating Ni-P composite coating in 3.5% NaCl aqueous solution was evaluated, and also analyzed by electrochemical polarization measurement. Experimental results indicated that electrolessplating Ni/P composite coating has high hardness, good corrosion resistance, particularly owing to the anodizing treatment of aluminum alloy. The anodizing treatment of AA7075 aluminum alloy substrate efficiently improved the adhesion, surface morphology and hardness of the electroplated Ni/P composite coating. The results also indicated that the anti-SCC of the coating is potentiodynamic polarization significantly increased in 3.5% NaCl aqueous solution.