Effect of HCOOH Vapor Adsorption on the Corrosion Performance of Cu‐0.2%P Tube

In this study, Cu‐0.2%P tube specimens were vertically exposed to a 0.04 vol.% HCOOH vapor environment for 3, 5, and 7 weeks. The height‐dependent corrosion behavior of the tubes was systematically analyzed using OM, CT, SEM‐EDS, EDS, XRD, and EBSD. The results indicate that the adsorption of HCOOH causes differences in droplet sizes on the upper and lower sections of the Cu‐0.2%P tubes, leading to the formation of liquid films with varying thicknesses. The thickness of the liquid film significantly influences the diffusion of oxygen. On the upper section, the thinner film promotes oxygen diffusion, resulting in more severe corrosion. In contrast, on the lower section, the thicker film retards oxygen diffusion, leading to milder corrosion.