Role of electrolyte additives on in-vitro corrosion behavior of DC plasma electrolytic oxidization coatings formed on Cp-Ti

The present investigation reports the effect of different electrolyte additives on in-vitro corrosion behavior of the plasma electrolytic oxidation (PEO) coatings formed on commercially pure titanium (Cp-Ti). PEO coatings were produced using a pulsed DC power source at a constant current density of 70 mA/cm(2) and a treatment time of 8 min. Different coatings were developed with different additives (sodium sulfate, Tris, di-ammonium hydrogen phosphate and ammonium acetate) added to a base electrolyte consisting of TSOP and KOH. PEO coatings were characterized for phase composition, elemental composition, surface and cross-sectional microstructure, corrosion behavior, apatite forming ability and osteoblast cell adhesion. The corrosion resistance of the developed oxide coatings was evaluated in a Kokubo simulated body fluid (SBF) by potentiodynamic polarization test and EIS study. The in-vitro bioactivity of all the PEO coatings and the untreated substrate was studied by soaking the samples in an SBF environment for 21 days. The TiO2 layer formed in phosphate, sulfate and nitrite containing electrolyte highly enhances the apatite formation in SBF. An in-vitro cell adhesion test was performed on all coatings using human osteosarcoma cells for 48 h. SEM images of cell adhesion test showed that human osteosarcoma cells were well adhered and spread on all PEO treated samples. Among all the additives, Tris has provided higher corrosion resistance in the SBF environment with good apatite forming ability and osteoblast cell adhesion. (C) 2016 Elsevier B.V. All rights reserved.