Evaluation of corrosion behaviour of tantalum coating obtained by low pressure chemical vapor deposition using electrochemical polarization

Abstract
Tantalum coatings are elaborated on titanium substrates through Low Pressure Chemical Vapor Deposition from tantalum pentachloride-hydrogen gaseous phase at a deposition temperature of 800°C and a total pressure of 3.3 mbar. The aim of this paper is to evaluate the effectiveness of this tantalum coating in corrosive solution. Optical Microscopy and Scanning Electron Microscopy observations reveal that deposits are of 1.7 µm in thickness and conformal. The corrosion resistance of tantalum coated titanium substrates is quantified through standard potentiodynamic polarization method. Even for tantalum coatings exhibiting some defects as pores, the corrosion current density is as low as 0.25 mA/cm².in very agressive solutions like kroll reagent (HNO₃/HF).