NiTi cladding on stainless steel by TIG surfacing process Part II. Corrosion behavior

Thick NiTi coatings were deposited on AISI 316 stainless steel samples by the tungsten inert gas (TIG) surfacing process. In Part I, the composition, microstructure and cavitation erosion behavior of the NiTi deposit were investigated. In Part II, the corrosion behavior of the NiTi deposit in 3.5% NaCl solution at ambient temperature was studied by electrochemical methods. Based on the results of cyclic potentiodynamic polarization tests, the corrosion resistance of the NiTi deposit in NaCl solution was found to be comparable to, but lower than, that of AISI 316. Compared with bulk NiTi, the corrosion resistance of the TIG-deposited cladding was reduced due to the presence of pores and a more heterogeneous microstructure. The galvanic effect between the NiTi deposit and the 316 steel substrate was minimal, as evidenced by a low galvanic current density relative to the uncoupled corrosion current density for the anodic member. The results of these corrosion tests indicate that TIG-deposited NiTi cladding is compatible with AISI 316 stainless steel and may be employed as local protection against cavitation erosion in NaCl solutions.