Surface Degradation of Stainless‐Steel Thruster Components Under Iodine Plasma Exposure

Iodine based electric propulsion systems offer significant advantages over conventional xenon systems, including lower cost, higher propellant density, and simplified storage as a solid at low temperatures. However, the corrosive nature of iodine vapors and plasma presents a critical challenge for long term spacecraft operation. This work investigates the degradation mechanisms of stainless steel 304, a common thruster construction material, under accelerated iodine plasma exposure simulating up to 5 years of operation in space conditions. Using optical emission spectroscopy (OES), we confirmed the presence of atomic iodine species in the plasma. Surface characterization through scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed progressive formation of circular corrosion sites with an average diameter of 1.9 µm and significantly increased surface roughness. Extended exposure led to merging of these sites into larger, irregular patterns. Energy dispersive x‐ray spectroscopy (EDX) indicated that surface oxidation is the primary corrosion mechanism, with evidence of continuous surface delamination in severely degraded regions. Notably, x‐ray diffraction (XRD) showed no bulk phase changes in the steel, indicating surface localized degradation. These findings demonstrate that iodine plasma induced corrosion is dominated by oxidation processes, which may be intensified in oxygen rich low Earth orbit environments.