Design and Characterization of Phosphatizing Coatings for Magnesium Implants

Area of Science:

• Biomaterials Science
• Materials Engineering
• Corrosion Science

Background:

• Magnesium alloys are promising for biodegradable implants but suffer from rapid corrosion in physiological environments.
• Developing protective coatings is crucial to control magnesium alloy degradation for clinical use.

Purpose of the Study:

• To develop a cementitious coating that induces magnesium phosphate formation on magnesium AZ31 alloys.
• To evaluate the coating's effectiveness in preventing corrosion and assess its biocompatibility for implant applications.

Main Methods:

• Comparative analysis of alloy surfaces in orthophosphoric acid (OPA) with various additives.
• Dip-coating of AZ31 alloys with optimized OPA-based suspension.
• Characterization using SEM, EDX, XRD, gravimetric, pH, and electrochemical analyses.
• In vitro cell culture tests to assess biocompatibility.

Main Results:

• OPA solutions saturated with magnesium ions effectively limited surface degradation.
• The developed coating formed magnesium phosphates and other phases, providing passivation even in high chlorine concentrations.
• Thermally cross-linked hydroxyethyl cellulose (HEC) improved coating stability and retarded degradation.
• Coated AZ31 alloys demonstrated biocompatibility and potential bioactivity in cell culture tests.

Conclusions:

• The phosphatizing coating strategy offers a promising method for controlled biodegradation of magnesium implants.
• This approach addresses the limitations of rapid corrosion, enabling wider clinical application of magnesium alloys.