Fabrication and corrosion property of novel 3-aminopropyltriethoxy-modified calcium phosphate/poly(lactic acid) composite coating on AZ60 Mg alloy

To improve the corrosion resistance of AZ60 Mg alloy as orthopaedic implants in human body, a novel 3-aminopropyltriethoxy-calcium phosphate/polylactic acid (APTES-CaP/PLA) composite coating was successfully prepared on AZ60 Mg alloy. 3-aminopropyltriethoxy (APTES) was introduced to enhance the interfacial strength between CaP and PLA in the CaP/PLA composite coating. CaP coating was first prepared by chemical conversion method prior to its surface silanization with APTES, and then was dip-coated with PLA to prepare APTES-CaP/PLA composite coating. The as-prepared APTES-CaP/PLA coating presented a more uniform and defectless surface compared with the unmodified CaP/PLA coating. The FTIR spectra confirmed the successful coupling of APTES with CaP and PLA. Electrochemical tests and 7-day immersion test were conducted in the simulated body fluid (SBF) at 37 °C, and whose results indicated that the corrosion resistance of the composite coating was improved obviously after the introducing of silane coupling agent. The interfacial adhesion strength was characterized by Tape Test method according to ASTM D3359-93, which showed that the interfacial strength of the composite coating was greatly enhanced. These results demonstrated that the APTES-CaP/PLA coating had great potential on facilitating the clinical application of Mg-based orthopaedic implants because of its excellent degradation resistance in body fluid environment.