Many manufacturing industries have been impacted by the innovation of additive manufacturing (AM), and biomaterials manufacturing is no exception. One group of biomaterials impacted by the innovation of 3D printing are degradable biomaterials. Degradable biomaterials could eliminate the need for surgery to remove the implant. 3D printed porous degradable biomaterials provide both mechanical support and space for bone ingrowth. As of today, there is an absence of materials for this application that are biodegradable, biocompatible and can be 3D printed. Magnesium can be used as a degradable biomaterial but its corrosion resistance is not yet adequate for application in the human body. Applying zinc as an alloying element to magnesium increases its corrosion resistance compared to pure magnesium. As the addition of alloying elements changes the microstructure, which in turn changes its corrosion behaviour.

This thesis analysed the effect of microstructure on the corrosion behaviour of extrusion-based 3D printed porous Mg-4Zn (wt.%) scaffolds, using localised electrochemical techniques i.e. scanning Kelvin probe force microscopy (SKPFM) and scanning electrochemical microscopy (SECM). The microstructure of the Mg-4Zn scaffolds includes grains with secondary phases precipitated along the grain boundaries with the presence of micropores. The secondary phase particles showed increased Volta-potential compared to the magnesium-based matrix. Therefore, the addition of zinc caused micro-galvanic coupling between secondary phase particles and the matrix, but their contribution to corrosion is minimal due to postponed contact with the electrolyte and the protection by the corrosion products. Micropores in the Mg-4Zn scaffold increased the surface exposed to fluids and were pitting corrosion initiation sites. During corrosion however, the surface was covered with a more stable corrosion product compared to pure magnesium. As a result of this, the corrosion resistance of Mg-4Zn scaffolds is better than pure magnesium scaffolds.