Highly Dispersed Cu Produced by Mechanical Stress-Activated Redox Reaction to Establish Galvanic Corrosion in Fe Implant

Abstract

Fe has immense potential for biodegradable orthopedic applications, but it degrades slowly in the physiological environment. Inducing galvanic couple by alloying Cu to Fe using ball milling is a promising approach. However, the ductile nature of Cu leads to the cold welding of a large amount of Cu powder during ball milling, which makes it difficult to disperse uniformly in the Fe matrix. Here, a Fe−CuO implant with highly dispersed Cu particles in the matrix was developed by shift-speed ball milling and selective laser melting. Specifically, copper oxide (CuO) particles were selected as precursors and dispersed in Fe powders by ball milling since they were brittle and would not be cold-welded during ball milling. After further milling in higher energy, it was found that CuO particles reacted with Fe and generated Cu particles through a stress-activated redox reaction. Subsequently, the obtained powders were prepared into a Fe−CuO implant using selective laser melting. Microstructure examination revealed that the Cu phases in the implant were dispersed evenly in the Fe matrix, which was considered to establish a large number of galvanic couples and aggravated the galvanic corrosion tendency. Electrochemical tests indicated that the implant had improved performance in degradation behavior in terms of high corrosion current density (22.4 μA/cm 2 ), low corrosion resistance (1319 Ω cm 2 ), and good degradation stability. In addition, it presented antibacterial effects against Escherichia coli and Staphylococcus aureus by diffusion mechanisms with killing rates of 90.7 and 96.7%, respectively, as well as good cytocompatibility.

Corrosion Prevention of Biomedical Implants: Surface Coating Techniques Perspective

“…It is one of the physical characteristics that determine the corrosion of biomedical implants, the other being the thermodynamic forces (redox reactions). [14][15][16] This method of preventing corrosion is mostly affected by fretting action which ruptures the coated layer and initiates cracks and forms metal atoms on the surface capable of accelerating corrosion. [17] Thus, coating materials must possess high abrasion resistance and must be impervious and non-toxic to the human body.…”

“…One of the most effective methods for preventing corrosion is by the use of a surface oxide layer coating technique acting as a kinetic barrier. It is one of the physical characteristics that determine the corrosion of biomedical implants, the other being the thermodynamic forces (redox reactions) [14–16] . This method of preventing corrosion is mostly affected by fretting action which ruptures the coated layer and initiates cracks and forms metal atoms on the surface capable of accelerating corrosion [17] .…”