Polymethylhydrosiloxane Coating Enhanced Corrosion Resistance of Hydrofluoric Acid Treated Mg Bio-implant Material in Simulated Body Fluid Solution

Abstract

Deceleration of the corrosion rate of Mg by surface chemical method via hydrofluoric acid treatment has a special interest because it is a simple, cost-effective, and efficient method for the coating of interior as well as the exterior part of any size and shape of implant material. However, conversion coating by hydrofluoric acid treatment fails to produce a long-term stable coating of Mg in ionic solutions caused by the formation of cracks on the surface during the process. Consequently, the corrosive ions of the SBF solution enter through the cracks that accelerate the dissolution by local galvanic corrosion. On the above view, we aim to develop a simple strategy for enhancement of corrosion resistance of the hydrofluoric acid treated Mg bioimplant material. This method is comprised of dip coating of hydrofluoric acid treated Mg sample in the polymethylhydrosiloxane followed by curing at 170°C for 30 min. The samples were characterized by electron probe microanalysis, X-ray photoelectron spectroscopy and electrochemical test. The electrochemical test results reveal that the corrosion rate of the coated Mg sample in the simulated body fluid solution is decreased by more than 8500 times than the bare sample. The long term immersion data indicate that the chemical resistance of the coated Mg sample in the SBF solution even after 25 days is better than the bare Mg metal. Polymethylhydrosiloxane coating is efficient to enhance the corrosion resistance of hydrofluoric acid treated Mg metal in simulated body fluid solution.