Plasma electrolytic oxidation (PEO) coatings were formed on cast A356 aluminum alloy by applying various process parameters (current density, duty cycle and processing time) in silicate based electrolyte. The phase composition of coatings was analyzed by x-ray diffraction (XRD), surface and cross section morphology and microstructure of coatings were characterized by scanning electron microscope (SEM). The Results of x-ray diffraction showed that all coatings are composed of gamma alumina. Coating produced in higher current density, duty cycle and time was more compact with fewer amounts of defects. Thickness and roughness of coatings surfaces were measured by Eddy current gauge and surface roughness tester, respectively. The thickness of the Coatings was in the range of 3–7 μm and it increased by increasing current density and time, but duty cycle did not have a noticeable effect on it. Corrosion resistance of bare and coated samples was evaluated by polarization test in 3.5 wt% NaCl solution. Sample S176 showed the best corrosion resistance with corrosion current density of 4.17נ10⁻⁸ A.cm⁻² and polarization resistance of 6.31נ10⁵ Ω.cm² that attributed to its more dense structure.

通过在硅酸盐电解质中应用各种工艺参数（电流密度、占空比和处理时间），在铸造 A356 铝合金上形成等离子体电解氧化 (PEO) 涂层。通过X射线衍射（XRD）分析涂层的相组成，通过扫描电子显微镜（SEM）对涂层的表面和截面形貌和微观结构进行表征。X 射线衍射结果表明所有涂层均由γ 氧化铝组成。以更高的电流密度、占空比和时间生产的涂层更紧凑，缺陷量更少。涂层表面的厚度和粗糙度分别用涡流仪和表面粗糙度仪测量。涂层的厚度在 3-7 μ的范围内m 并且它随着电流密度和时间的增加而增加，但占空比对其没有明显影响。通过在 3.5 wt% NaCl 溶液中的极化测试评估裸露和涂层样品的耐腐蚀性。样品S176表现出最好的耐腐蚀性，腐蚀电流密度为4.17נ10 ^-8 A.cm ^-2，极化电阻为6.31נ10 ⁵ Ω.cm ²，这归因于其更致密的结构。