School of Materials Science and Engineering, Yeungnam University, Gyeongsan 38541, Republic of Korea.
Sci Rep. 2017 Mar 10;7:44458. doi: 10.1038/srep44458.
Plasma electrolytic oxidation (PEO) was a promising surface treatment for light metals to tailor an oxide layer with excellent properties. However, porous coating structure was generally exhibited due to excessive plasma discharges, restraining its performance. The present work utilized ethylenediaminetetraacetic acid (EDTA) and Cu-EDTA complexing agents as electrolyte additives that alter the plasma discharges to improve the electrochemical properties of Al-1.1Mg alloy coated by PEO. To achieve this purpose, PEO coatings were fabricated under an alternating current in silicate electrolytes containing EDTA and Cu-EDTA. EDTA complexes were found to modify the plasma discharging behaviour during PEO that led to a lower porosity than that without additives. This was attributed to a more homogeneous electrical field throughout the PEO process while the coating growth would be maintained by an excess of dissolved Al due to the EDTA complexes. When Cu-EDTA was used, the number of discharge channels in the coating layer was lower than that with EDTA due to the incorporation of CuO and CuO altering the dielectric behaviour. Accordingly, the sample in the electrolyte containing Cu-EDTA constituted superior corrosion resistance to that with EDTA. The electrochemical mechanism for excellent corrosion protection was elucidated in the context of equivalent circuit model.
等离子体电解氧化 (PEO) 是一种有前途的轻金属表面处理方法，可以定制具有优异性能的氧化物层。然而，由于等离子体放电过度，通常会表现出多孔涂层结构，从而限制了其性能。本工作利用乙二胺四乙酸 (EDTA) 和 Cu-EDTA 络合剂作为电解质添加剂，改变等离子体放电，以提高 PEO 处理的 Al-1.1Mg 合金的电化学性能。为了达到这个目的，在含有 EDTA 和 Cu-EDTA 的硅酸盐电解质中，通过交流电制备了 PEO 涂层。发现 EDTA 络合物可以改变 PEO 过程中的等离子体放电行为，使涂层的孔隙率低于没有添加剂的情况。这归因于在整个 PEO 过程中形成更均匀的电场，而 EDTA 络合物会使溶解的 Al 过剩，从而保持涂层的生长。当使用 Cu-EDTA 时，由于引入了 CuO 和 CuO 改变了介电性能，涂层中的放电通道数量比 EDTA 少。因此，含有 Cu-EDTA 的电解质中的样品的耐腐蚀性优于含有 EDTA 的样品。根据等效电路模型，阐述了优异的腐蚀保护电化学机制。
