Influence Of Anions Associated Corrosion Products On Long-term Biodegradation Of Zinc In Vitro

Biodegradable zinc as well as its alloys have been widely considered as new biodegradable metal material,because of its good mechanical properties,suitable corrosion rate,unquestionable biosafety and biocompatibility.Nevertheless,developing Zn biodegradable metal is still in its infancy and some concerns need still to be resolved;particularly the degradation profile of Zn in the context of biomedical applications is yet to be established.To our best knowledge,there has been rarely report about the impact of corrosion products on the degradation behavior of Zn.In fact,the formation,existing and dissolution of corrosion products during the process of service can shape the degradation manner of biodegradable Zn with regard to both corrosion rate and mode.Therefor their influence on the degradation of zinc are important and worth elucidating;and more importantly their individual and combined effects need to be fathomed.In this study,we aimed to distinguish the individual impacts of anions(SO₄^2-,HCO₃^-and HPO₄^2-)-associated corrosion products on the short-term degradation of zinc.Briefly,the simulated single corrosion products were deposited on Zn for the first time by liquid deposition with respective anions contained solutions.According to the surface morphology and chemical composition results,the three anions tend to generate distinct products layer of different features.The results of electrochemical corrosion behavior?EIS and Polarization?as a function of immersion time discloses that the pre-deposited products layer may elicit distinctive impacts on the degradation of Zn:The phosphate product pre-deposited Zn performed best with highest electrochemical corrosion resistance as well as slowest degradation rate;whereas the sulfate and carbonate products pre-deposited were poor in the stability and protection against corrosion of Zn.The joint compact of the anions-associated products were looked into via the formation,existing and dissolution of corrosion products in vitro immersion degradation of zinc in simulated body fluid(including SO₄^2-,HCO₃^-and HPO₄^2-)up to 21 days and fathomed in terms of their distinctive contributions,ascertained to shape the dynamic and kinetic degradation profile of Zn.It was found that sulfate or carbonate products can hardly accumulate probably because of their high solubility.The protected areas however seem to accrue phosphorus contained compounds that are protective and stable.In particularly,the complete covering of phosphate products had the strongest protection efficacy of degradation,whereas the porous form on the corrosion pit may promote the underneath corrosion due to the formation of autocatalytic effect and galvanic corrosion model.And last,the corresponding corrosion model was established to deeply explore the influence of corrosion products on long-term biodegradation of zinc in vitro.