Acetic Acid Etching of Mg-xGd Alloys

Abstract

Mg-xGd alloys show potential to be used for degradable implants. As rare earth containing alloys, they are also of special interest for wrought products. All applications from medical to engineering uses require a low and controlled degradation or corrosion rate without pitting. Impurities from fabrication or machining, like Fe inclusions, encourage pitting, which inhibits uniform material degradation. This work investigates a suitable etching method to remove surface contamination and to understand the influence of etching on surface morphology. Acetic acid (HAc) etching as chemical surface treatment has been used to remove contamination from the surface. Extruded Mg-xGd (x = 2, 5 and 10) discs were etched with 250 g/L HAc solution in a volume of 5 mL or 10 mL for different times. The microstructure in the near surface region was characterized. Surface characterization was done by SEM, EDS, interferometry, and ToF-SIMS (time-of-flight secondary ion mass spectrometry) analysis. Different etching kinetics were observed due to microstructure and the volume of etching solution. Gd rich particles and higher etching temperatures due to smaller etchant volumes promote the formation of pits. Removal of 2–9 µm of material from the surface was sufficient to remove surface Fe contamination and to result in a plain surface morphology.

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“…In addition, the thin films formed on the surface also help in passivation and thereby reduce the degradation. The treatment also helps in improving the surface energy favorable for cell adhesion and proliferation (Gawlik et al, 2019;Rahim et al, 2020). Mao et al (2013) treated Mg-Nd-Zn-Zr alloy in 40% (vol.)…”

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“…Four research articles and one review paper have been published in this Special Issue of Metals. The subjects cover studies on corrosion behavior and its characterization in in-vitro environments [1][2][3] and in vivo studies on facial reconstruction [4,5]. Mainly Al-free alloys, Mg-Gd [1], Mg-Zn-Ca [2], Mg-Dy-Nd [3], and Mg-Zn-Zr [5] and its corrosion morphology are the focus of papers in this Special Issue.…”

“…The first article by Gawlik et al [1] on "Acetic Acid Etching of Mg-xGd Alloys" investigates a suitable etching method, here acetic acid (HAc) etching, to remove surface contamination and to understand the influence of etching on surface morphology. Extruded Mg-Gd discs were etched with HAc solution in different volumes and times, to remove contamination from the surface.…”