Review of the corrosion behaviour in tannic-acid coated magnesium implants

Abstract

Magnesium is a bio-degradable material used for bone implants because of its similar mechanical properties to bones. However, magnesium has a high corrosion rate, resulting in an implant’s degradation before the bone is fully healed. Thus, researches are conducted to study ways to improve the corrosion resistance of magnesium. Coating is one of the methods to hinder the corrosion rate of magnesium. There are two types of coatings: organic and inorganic. Organic coatings are preferable due to their non-toxicity and good biocompatibility. Tannic acid (TA) is an organic coating with a strong bond with magnesium due to its many hydroxyl groups. Besides bonding with the substrate material, tannic acid can also bind with other compounds or elements to improve the performance of the coating layer. This review evaluated several types of TA-based coatings on magnesium alloys used in orthopaedic implants and the fabrication processes affecting the structural integrity of the coating. The strategies for using TA-compound combination for corrosion mitigation with ease of fabrication process were also highlighted. This review is expected to provide some insight on the challenges and future directions of TA-based magnesium coatings for orthopaedic applications.

Keywords

• corrosion resistance
• degradation rate
• biodegradable materials
• surface coating
• biocompatible coating