交流電解粗化鋁板蝕孔衍生與腐蝕膜生成機制

Etch Pit Nucleation and Growth and Etch Film Formation of the AC Electrograined Aluminum Plates

本研究針對平版印刷用鋁板進行一系列交流電解粗化，藉以了解蝕孔衍生成長機構與腐蝕膜的生長機制。實驗結果顯示在硝酸液中含腐蝕膜的粗化表面呈現高度的包旋表面，所衍生的蝕孔為半圓形蝕孔，相反地，在鹽酸液中粗化的含腐蝕膜鋁板表面包括包旋蝕孔區域與平坦區域。橫截面穿透式電子顯微鏡觀察進一步發現在硝酸中生成的腐蝕膜為層狀結構，而在鹽酸中生成的蝕孔上覆蓋著單層結構的腐蝕產物，同時在硝酸或鹽酸中生成的腐蝕膜為多孔質非晶態氫氧化鋁。在硝酸中以正弦波與方形波交流電源所得蝕孔大都呈現半圓形，其中在正弦波下生成的腐蝕膜為層狀結構，且蝕孔大小較為均勻，方形波下生成的腐蝕膜除了有層狀結構外，同時具有沈積膜形式，蝕孔大小較不均勻。當正半週期電量增加時，腐蝕膜變薄，粗化表面蝕孔由均勻粗化之包旋蝕孔轉變成不均匀粗化的粗大圓形蝕孔。負半週期電量增加時，鋁板表面覆蓋厚實腐蝕膜，腐蝕膜生成阻礙了電解液的侵蝕，降低蝕孔數量與大小。

Lithographic printing aluminum plate was systematically ac electrograined to investigate the nucleation and growth of the etch pit and the formation of the etch film. When electrograined in nitric acid, the as-grained Al exhibited a highly convoluted surface dotted with hemispherical etch pits. In contrast, the surface of the Al electrograined in hydrochloric acid consisted of convoluted and relatively-flat areas. Cross-sectional transmission electron microscopy (TEM) further revealed the etch film formed in nitric acid exhibited a layered structure, whereas that formed in hydrochloric acid was a single layer. In addition, the etch film was identified as a porous Al hydroxide regardless of the electrolyte. Although the etch pits formed in nitric acid using the sinusoidal and square current waveforms were hemispherical, the pit size associated with the Al electrograined using the sinusoidal current was more uniform than that electrograined using the square current. Moreover, the etch pit formed using the square current was covered with a layered etch film and the mouth of the layered etch film was completely filled with etch product. Finally, with increasing the charge of the anodic to cathodic half cycle, the thickness of the etch film decreased and the Al was non-uniformly grained. Conversely, the amount of the etch film increased when the charge ratio of the cathodic to anodic half cycle increased, thereby reducing the attack of the Al by the electrolyte, which in turn, reduced the density and size of the etch pit.