超塑性Zn-22wt.%Al合金表面陽極著色處理

Anodic Surface Coloring Treatment for a Superplastic Zn-22wt.% Al Alloy

本研究針對一種外覆超塑性Zn22Al合金薄片之創新防電磁波干擾塑膠外殼的防蝕與外觀需求，研發此超Zn22Al合金表面陽極著色處理，其製程分為兩階段處理：第一段是在鹼性溶液中利用60V（60Hz）定電壓，將超塑性Zn22AI合金表面產生鈍態的氧化障蔽層，再利用第二階段定電流效應，讓電壓上昇至障蔽層崩潰而產生火花放電效應，產生具有覆膜組織。此陽極著色處理表面利用SEM/EDS、EPMA及電化學進行分析，結果顯示：覆膜之表面形態為火山狀多孔性組織，主要組成為矽、鋁、鋅、鈉與氧，另鑲入過渡金屬離子，推斷覆膜結構主要為矽酸鋁鹽之氧化物，同時表面保有鋅鹽特性，此硬質覆膜具有良好抗腐蝕性。

This study deals with the demand for corrosion-resistance and a concern for sightly appearance in the case of innovative anti-electromagnetic interference plastic enclosures cladded with superplastic Zn22Al thin metallic sheets. For this purpose, the surface of Zn22Al has undergone an anodic coloring treatment. Two steps are involved in the manufacturing process: in the first step, a voltage of 60V (60Hz) is applied to the surface of the Zn22Al alloy in an alkaline solution to create a passive oxide barrier layer, while the second step is to increase the voltage applied to spur on the breakdown of the barrier layer as the spark discharge effect will be triggered to facilitate the formation of an anodic coating structure. Through SEM/EDS, EPMA and electrochemical tests, the anodic layer is analyzed in detail. The results show that the anodic layer has a porous volcano-like structure with a composition of Si, Al, Zn, Na, and O, which also contains embedded transition metal ions. The layer structure is proposed to be aluminum-fused silicate that retains a surface coating of zincate. Such an anodic layer is hard enough to attain great corrosionresistance results.