Analysis of the Efficiency of Different Treatments in Surface Passivation of NiTi

Svetlana Shabalovskaya

Thin passive NiTi surfaces with Ni-depleted sublayers and homogeneous chemical composition are needed to induce positive biological response, and minimize corrosion and nickel release in the human body. To achieve this goal, there are many approaches under development. Most of them fail either in the preparation of nickel- free surface sublayers or in passivation that results in actual or potential corrosion. Completely passive NiTi surfaces that have both alloy constituents stabilized still needs to be developed. Various surface treatments (chemical etching in acidic and alkaline solutions, electropolishing in different electrolytes, heat treatment in different media, gas plasma implantation, etc.) are analyzed in respect with surface passivation, types of oxide induced, their comparative biocompatibility, and corrosion resistance.