Deposition of anti-corrosion hybrid film of hexamethylene diaminetetrakis (methylene phosphonic acid)/hydroxyapatite on biodegradable Mg: Influence of deposition procedures

Magnesium and its alloys are promising biodegradable materials because of their light weight and superior mechanical properties. However, the high corrosion susceptibility of magnesium is the main obstacle that hinders the application of Mg in biomedical applications . In this article, two approaches have been employed to fabricate hybrid films of hexamethylene diamine tetrakis (methylene phosphonic acid) (HMDTMPA) and hydroxyapatite (HA) on Mg. The direct dipping method involves an immersion in a single solution containing both calcium, phosphate, and the organic compound. However, it results in poor-quality loose films, due to unstable film of monocalcium phosphate monohydrate (MCPM). The other method involves immersion in two separated solutions: Ca-P solution and HMDTMPA solution. Our results showed that the corrosion resistance was enhanced about 12-times compared with HMDTMPA film due to the formation of a stable hybrid film of dicalcium phosphate dihydrate (DCPD). The mechanism of formation of anti-corrosion DCPD was discussed on the light of SEM, EDS , FTIR , XRD and XPS.