Fabrication of biodegradable superhydrophobic Zn-Fe coating on ultra-light Mg-Li alloy

Abstract

As a typical biodegradable and biocompatible light metal, magnesium (Mg) and its alloys exhibit significant prospects for various applications, especially in biomedical materials. Unfortunately, their actual application fields have been restricted by too fast degradation/corrosion rate. Both zinc (Zn) and iron (Fe) are biodegradable and biocompatible but stabler thermodynamically. It's one of the considerable refreshing strategies for controlling the degradation rate of Mg substrate by constructing a ZnFe coating with superhydrophobicity on it. However, it's challenging and rarely reported due to the high chemical reactivity of Mg. This study reports the successful in-situ synthesis of ZnFe coatings with hierarchical micro-/nano-scale structures and superhydrophobicity on ultra-light MgLi alloy by employing an innovative weak alkaline aqueous bath followed by simple chemical modification. Their micromorphology, chemical and phase compositions as well as surface wettability were comprehensively analyzed by FE-SEM, EDS, XRD, XPS, FT-IR, and a contact angle measuring instrument. Furthermore, the degradation behavior of the typical samples was evaluated by modern electrochemical measurement technology. The results revealed that the coating comprised dense micro-papillary structures and nanosheets, exhibiting a static contact angle of droplets up to 161.5° and a sliding angle of 3.0°. In addition, the obtained sample demonstrated a significantly reduced degradation rate compared to the bare magnesium alloy.