Anodic dissolution and passivation mechanisms of 07Cr16Ni6 in K3Cit solution and its electrochemical machining for microstructure

Abstract

The complexation mechanism, passivation-related behaviors and interface structures of 07Cr16Ni6 in K₃Cit solution were clarified. Cit^3– contend against OH⁻ for cationic, leading to the formation of tetra- or hexa-dentate complexes. The anodic dissolution behaviors revealed passive and transpassive behaviors. Passivation film presented a more capacitive, thicker, stable inner film and a weaker, thinner outer film, and the external and internal films were around 3 nm and 24 nm, respectively. Current efficiency increases gently, then rises steeply, finally stabilizes. The lath-type martensite dispersed on machined surface improved substantially as the current density increased. Finally, the anodic dissolution characteristic models and a high quality round hole were fabricated. The experimental results have proved the feasibility to manufacture high-quality metallic bipolar plates through electrochemical machining on 07Cr16Ni6 alloy in K₃Cit solution.