Influence of surface modification on the in vitro corrosion rate of magnesium alloy AZ31

Abstract

In recent years, magnesium alloys have been proposed as a new class of metallic bioabsorbable implant material. Unfortunately, the production of hydrogen gas and an increase in alkalinity are both by-products of the degradation process of these materials. This necessitates the development of magnesium alloys with controlled degradation rates. Furthermore, biocompatible coatings that can delay the onset of corrosion would ensure that the mechanical integrity of the implant remains intact in the early stages of healing. This article explores the influence of surface modification by biomimetic calcium phosphate coating, biodegradable polymer coatings, and acid etching on the corrosion rate of the AZ31 magnesium alloy in simulated body fluid. Our results indicate that all of these surface treatments have a positive impact on the corrosion rate of the material and that in the early stages of implantation it is possible to tailor the corrosion rate through an appropriate choice of surface treatment.

Design and assessment of a wrapped cylindrical Ca‐P AZ31 Mg alloy for critical‐size ulna defect repair

“…These ions and concentrations were chosen for their roles in calcium phosphate formation. 28 The samples were dried under vacuum for 1 hour after which surfaces were examined visually using a Quanta 200 Environmental Scanning Electron Microscope (ESEM) for elemental analysis. The ESEM was used in a ''low vacuum'' mode with the 20 kV electron beam accelerating voltage and a 4 lm spot size.…”

“…This could reduce the corrosion rate in the initial stages allow time for bioresorption of degradation products, and reduce local basicity. 28 Even though the coating will eventually degrade to expose the Mg surface, this will increase time for a bony callus to form around the implant. 5 Substantial reduction in corrosion rates have been studied using polyester coatings in vitro.…”

“…5 Substantial reduction in corrosion rates have been studied using polyester coatings in vitro. 28 Recently, biodegradable amorphous silica coatings have also been employed to reduce initial corrosion rate. 29 For orthopedic applications, the majority of recent studies use Mg alloys in the form of a solid monolith (bar or rod form).…”

Effect of Adding Sb on Microstructure, Mechanical Properties and in <i>Vitro</i> Degradation Behavior of as Cast Mg-4wt% Zn Alloy for Medical Application

“…Seeing that the biomimetic coating would be helpful in coating biodegradable substrates such as Mg-alloys, it reduces the incubation times in SBF during the coating procedure [12]. As reported this resulted in the formation of non-uniform and porous Ca-P coating on Mg substrates [13], in addition to hydrogen bubbles formed on the Mg surface during immersion. When using a Sol gel technique for Mg substrates, the temperatures should be less than the melting point of pure Mg (650˚C) [14] to avoid affecting the surface integrity of the Mg substrate.…”

Surface Modification of Magnesium and its Alloys Using Anodization for Orthopedic Implant Application

“…Surface modification is considered one of the most useful and effective methods to control the initial degradation of Mg and its alloys [12]. Table 1 summarizes the previous research on Mg coating with different applied techniques and chemical composition.…”