Laser machined micropatterns as corrosion protection of both hydrophobic and hydrophilic magnesium

Yahya Efe Yayoglu; Ryan G Toomey; Nathan B Crane; Nathan D Gallant

doi:10.1016/j.jmbbm.2021.104920

Laser machined micropatterns as corrosion protection of both hydrophobic and hydrophilic magnesium

J Mech Behav Biomed Mater. 2022 Jan:125:104920. doi: 10.1016/j.jmbbm.2021.104920. Epub 2021 Oct 25.

Authors

Yahya Efe Yayoglu¹, Ryan G Toomey², Nathan B Crane³, Nathan D Gallant⁴

Affiliations

¹ University of South Florida Mechanical Engineering, ENG030, Tampa, FL, 33620, USA.
² University of South Florida Chemical and Biomedical Engineering, ENG030, Tampa, FL, 33620, USA.
³ Brigham Young University Mechanical Engineering, 350 EB, Provo, UT, 84602, USA.
⁴ University of South Florida Mechanical Engineering, ENG030, Tampa, FL, 33620, USA. Electronic address: ngallant@usf.edu.

PMID: 34768114
DOI: 10.1016/j.jmbbm.2021.104920

Abstract

Magnesium and its alloys are promising candidate materials for medical implants because they possess excellent biocompatibility and mechanical properties comparable to bone. Furthermore, secondary surgical operations for removal could be eliminated due to magnesium's biodegradability. However, magnesium's degradation rate in aqueous environments is too high for most applications. It has been reported that hydrophobic textured surfaces can trap a surface gas layer which acts as a protective barrier against corrosion. However, prior studies have not investigated separately the role of the texture and hydrophobic treatments on magnesium corrosion rates. In this study, pillar-shaped microstructure patterns were fabricated on polished high purity magnesium surfaces by ablation with a picosecond laser. Some micropatterned samples were further processed by stearic acid modification (SAM). Micropatterned surfaces with SAM had hydrophobic properties with water droplet contact angles greater than 130°, while the micropatterned surfaces without SAM remained hydrophilic. The corrosion properties of textured and smooth magnesium surfaces in saline solution were investigated using electrochemical impedance spectroscopy (EIS) and optical microscopy. Corrosion rates on both hydrophobic and hydrophilic laser machined surfaces were reduced ∼90% relative to polished surfaces. Surprisingly, corrosion rates were similar for both hydrophobic and hydrophilic surfaces. Indirect evidence of local alkalization near microstructures was found and was hypothesized to stabilize the Mg(OH)₂ layer, thereby inhibiting corrosion on hydrophilic surfaces. This is different than the corrosion resistance mechanism for superhydrophobic surfaces which makes use of gas adhesion at the liquid solid interface. These results suggest additional processing to render the magnesium hydrophobic is not necessary since it does not significantly enhance the corrosion resistance beyond what is conferred by micropatterned textures.

Keywords: Biomaterials; Corrosion rate; Corrosion resistance; Degradable implants; Magnesium alloys.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Corrosion
Hydrophobic and Hydrophilic Interactions
Lasers
Magnesium*
Microscopy*

Substances

Magnesium