Effects of Various Adhesive Layers on Electrochemical Characteristics of 3D-Printed Polylactic Acid Coatings on AM60 Magnesium Alloy

The challenge of 3D-printed polymer coating performance on metallic substrates is using a proper adhesive layer. Thus, the effect of various adhesive layers on the electrochemical properties of polylactic acid (PLA) as bio-coatings was performed in this study. These coatings were fabricated through a fused deposition modeling 3D printer on AM60 magnesium alloys. Electrochemical properties were examined through electrochemical impedance spectroscopy (EIS) and Tafel polarization tests in a simulated body fluid solution during various exposure times. EIS measurements showed an increase in the impedance of all coatings by about 86–98% compared to the magnesium alloy. However, Tafel polarization indicated a reduction of 64–98% in the corrosion rate of PLA coatings. The obtained results showed that the highest impedance was related to a coating that was printed on a cyanoacrylate adhesive layer, and the surface of magnesium was etched in an acidic solution. The lowest impedance at low exposure time was also attributed to the PLA coating when the surface of substrates was polished. This was based on the adsorption of a high amount of water due to the Fourier-transform infrared spectra results. The applied anodizing pre-treatment was not an effective factor for the high exposure time based on the results of degradation in-vitro measurements.