Electrochemical investigations of PLA coatings deposited by fused filament fabrication on magnesium alloy in Ringer's solution

Abstract

In this paper, polylactic acid (PLA) layers were printed on AM60 magnesium alloy through a fused filament fabrication-3D printing manufacturing method, as a low-cost and innovative technology. Then, the effect of coating thickness and anodized layer as a binder on the electrochemical behavior of Mg substrates was investigated in Ringer's solution. Electrochemical impedance spectroscopy, Tafel polarization, and weight loss investigations were performed at various exposure times for 28 days to achieve this purpose. Corroded surfaces were also analyzed through field emission scanning electron microscopy images and Fourier-transform infrared spectroscopy patterns. The obtained results showed that the higher thickness of the layer with a value of 400µm was not effective in raising the PLA layer impedance without the anodized layer. However, the higher PLA thickness could have a key role in the corrosion rate reduction of PLA layers when printed on the anodized layer. The lowest corrosion rate with a value of 0.3µA/cm2 was related to the PLA-printed layer with a lower thickness (200µm) and without an anodized layer. This reduction range in corrosion current density was about 80.2-99.4% compared to the Mg alloy. The weight loss behavior of PLA layers during a long time of exposure was followed by a logarithmic function. The range of corrosion rate decrease was 9.7-32.2%. The PLA degradation mechanism was also suggested based on all obtained results.