Effect of Cl2 Gas Exposure on the Surface Properties of Electropolished STS316L

In this study, the surface characteristics-including roughness, oxide layer thickness, and composition-of the electropolished layer on STS316L steel tubes subjected to double melting via the VIM/VAR process were investigated after exposure to Cl 2 gas.The tubes were exposed to Cl 2 gas for 1 to 13 d to simulate semiconductor conditions.Surface roughness increased with Cl 2 exposure time, showing values of 0.01, 0.04, 0.04 and 0.03 m after 0, 1, 5 and 9 d, respectively.At the same time, the oxide layer thickness on EPed STS316L, which was initially 8.2 nm, decreased to 3.18, 2.58 after 1, 5 d of Cl 2 exposure, approaching the initial thickness of 2.38 nm observed on non-EPed STS316L.After 9 d, the thickness further decreased to 0.51 nm, with no significant change was observed thereafter.Before Cl 2 exposure, the CrO/FeO ratio was 2.26.After 1, 5, and 9 d of exposure, the ratio decreased to 2.06, 1.75, and 1.27, respectively.In addition, the penetration depth of Cl into the oxide layer increased with longer exposure time.These results suggest that the formation of chromium chlorides led to the breakdown of the stable Cr 2 O 3 layer.