<p>Carbon steel, widely used in nuclear reactor components, is prone to degradation under extreme conditions such as high radiation doses, temperature, and pressure. To increase their longevity, NASA HR-1 alloy was investigated as a protective coating because of its excellent mechanical strength and corrosion resistance. Cold spray deposition was utilized to coat NASA HR-1 onto the substrates, and the effects of process gases, such as nitrogen (N₂) and helium (He), on coating’s microstructure and corrosion behavior were systematically investigated. Microstructural characterization was conducted using optical microscopy, in situ hot-stage transmission electron microscopy, and scanning electron microscopy. NASA HR-1 coatings deposited using He process gas exhibited an average porosity reduction of ~ 95% compared to coatings deposited using N₂ process gas. Electrochemical testing via potentiodynamic polarization in 3.5 wt.% NaCl solution showed He cold-sprayed coatings had ~ 68 times lower corrosion rates than uncoated steel substrates. The 96-h salt fog tests also showed significantly reduced corrosion-induced weight difference in coated specimens, confirming that He cold sprayed coatings reduced material degradation by ~ 83%. Overall, using He as the process gas produced NASA HR-1 coatings with enhanced particle deformation, reduced porosity, and improved corrosion resistance, demonstrating strong potential for extending the structural component life in harsh environments.</p>