(EDTA)⁴⁻ supplements as superior modifier of the in-vitro-degradation properties of the magnesium alloy coated through discharge-assisted process

The (EDTA)⁴⁻ organic substituents were supplemented with alkaline silicates electrolyte, however in varying concentration to explore the microstructure, chemical composition and subsequent effects on the biodegradation of the PEO coated Mg AZ91 alloy. From surface analysis-, carried out through SEM, samples with zero-(EDTA)⁴⁻ were found-, lacking pancake structural features; however, supplementing electrolyte with (EDTA)⁴⁻, bulky and layered pancakes were obtained with minimum cracks and minimum porosity for EDT-1. From the phase and inner layer analysis, it was found that EDTA can significantly alter the surface layers composition and could act as a passivation agent-; however, individual polycrystalline phases were not found to form. The hardness value obtained for EDT-1 was ∼909.69 HV, the highest value found here which occurs with the shallowest indents found in this study. In-vitro degradation analysis was carried out using potentiodynamic polarization at room temperature, cyclic polarization at RT and high fever conditions (HFT ∼40 °C). The corrosion potential for coated AZ91 was obtained as a positive value of ∼ 0.1 V, for the first time in the PEO research; however, the results were not supported by the cyclic polarization tests at room temperature and at HFT. The post corrosion microstructural analysis confirmed the effective role of EDTA up to 1.0 g·L⁻¹ and revealed the formation of thin films during the forward polarization at HFT.