At severe corrosion, the loss of cross-sectional area is a suitable parameter for determining the residual mechanical performance. At the beginning of corrosion, pitting, if present, may be responsible for premature failure. Mg10Gd (extruded) tensile samples were corroded in Ringer’s acetate solution at half the circumference of the gauge length. µCT analysis was performed before (after corrosion) and after the tensile test. By the µCT scans it is possible to correlate the corrosion morphology with the fracture area and the surrounding corroded region. By analysing DIC strain and correlated stress maps the increased stress intensity could be identified and correlated with the corrosion morphology. This study makes clear that crack initiation can be independent of the smallest cross-section of the sample when pitting of critical shape, size and quantity occurs.

WE43 Mg alloy, known for its biodegradability, is extensively used in clinical applications such as bone screws, typically produced via conventional methods like casting and extrusion. The advent of 3D printing technologies, specifically Laser Powder Bed Fusion (LPBF), enables the creation of intricate and porous implants. Despite the potential benefits, a significant challenge for Mg-based lattice implants is their rapid degradation rate. This study addresses the variability in the degradation behavior of WE43 lattices since contradictory results were shown in the literature. The primary focus is on the influence of structural geometry, including unit cell configuration and relative density, and alloy microstructure on degradation rates. Initially, LPBF process optimization was undertaken to produce high-quality prints with minimal porosity. Various lattice structures, such as Triply Periodic Minimal Surfaces (TPMS) and strut-based lattices, alongside bulk samples, were fabricated to assess the impact of geometry on microstructure and corrosion behavior. Corrosion testing involved hydrogen evolution measurements in phosphate-buffered saline (PBS) over short-term (2 hours) and long-term (3 days) durations. Additionally, potentiodynamic polarization (PDP) and acoustic emission (AE) measurements were conducted to highlight localized corrosion mechanisms. Results indicated that high-density samples (up to 99.6%) were achieved. Strut-based lattice structures lost structural integrity within 2 hours, whereas TPMS and bulk samples retained integrity for 3 days. AE measurements, which correlated well with PDP curves, revealed instances of surface breakdown and re-passivation in bulk samples, with minimal structural damage indicated by constant AE amplitude. Conversely, strut-based lattices exhibited higher surface breakdown frequency, attributable to increased surface exposure and electrochemical pitting. In conclusion, structural geometry significantly influences the corrosion behavior of LPBF-fabricated WE43 Mg alloy. TPMS and bulk samples demonstrate superior corrosion resistance compared to strut-based lattices whose inherent sharp edges and corners act as initiation sites for localized corrosion. Insights from AE and PDP measurements highlight the necessity of optimizing strut thickness and orientation in lattice designs to balance mechanical performance and corrosion resistance. Future research will focus on designing optimized lattice structures to achieve this balance.

Magnesium and its alloys have significant potential as bone substitutes due to their bone-like mechanical properties and intrinsic biodegradability. However, their low corrosion resistance can impair their load-bearing capacity and interfere with the healing process by inducing an undesirable inflammatory response. In this context, electrochemical surface modification processes such as Plasma Electrolytic Oxidation (PEO) offer a promising way to control Mg corrosion by forming protective ceramic coatings that facilitate bone regeneration at the implant site. In this work, we focused on the tuning of novel pulsed bipolar PEO processes for the treatment of magnesium alloys in order to improve the protective effect of the coatings, with the aim of enhancing the suitability of the technique for prospective clinical applications.

The study’s aims were to assess how anodization and polymer coating affect the degradation process of LZ21 wire, measure the in vivo degradation rate of LZ21, and obtain an in vitro - in vivo correlation factor (IVIVC).