In vitro corrosion behavior of biodegradable WE43 alloy under various physiological flow velocities

In the present work, the influence of the simulated physiological flow field on the in vitro corrosion behavior of biodegradable WE43 (Mg-4.05 wt% Y-3.64 wt% RE-0.52 wt% Zr) magnesium alloy has been studied, using Hanks' balanced salt solution (HBSS) as the corrosion medium. The results indicate that the corrosion rate of WE43 alloy is time-dependent under each condition. After immersion for 168 h, the corrosion rate of WE43 alloy with a flow rate of 5.33 cm/s is about 3.49 mm/year, which is 1.7 times higher than that under static condition. The contradictory between the dynamic dissolution and re-deposition of the corrosion products is strongly related to the flow velocity. Initially, an accelerated mass transfer at a low flow rate would promote the corrosion layer generation of WE43 alloy, dominating the integrity of the corrosion layer, while continually high shear stress induced by a high flow rate field would destroy the integrity of the corrosion layer, primarily mitigate the thickness of the Ca-P layer. Owing to the corrosion product evolution and the influences of Cl⁻, the corrosion mode of the WE43 alloy herein transforms from localized corrosion to relatively uniform corrosion with the increase in flow rate.