<p>This study presents a chemical–mechanical polishing (CMP) process designed to achieve ultrasmooth surface finishes on SUS 304 steel. The process utilizes an eco-friendly slurry that is free from alkalis, strong acids, and harmful chemicals. The slurry is composed of nonylphenol ethoxylate (NP9), organic nicotinic acid, hydrogen peroxide, and deionized water. Unlike conventional machining methods that often result in surface scratches due to tool stamping errors, this CMP technique combines abrasive particle polishing with chemical reactions, leading to a nanometer-level surface finish. Systematic experiments were conducted to assess the impact of key parameters in the polishing process, including the rotational speed of the disk, polishing force, and the size and concentration of abrasive particles. The Taguchi orthogonal array design was employed to optimize surface quality and material removal rates. To elucidate the underlying mechanisms of the proposed CMP process, x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) analyses were performed. XPS analysis revealed that Cr ions undergo complexation with nicotinic acid, resulting in the formation of chelate compounds, which significantly enhance polishing efficiency. Furthermore, the analysis highlighted the dissolution of the oxide layer on the SUS 304 surface and the subsequent release of various Cr ions into the CMP slurry. These findings not only confirm the intricate chemical and mechanical interactions occurring during the polishing process but also demonstrate the efficacy of the proposed CMP method in producing high-quality surface finishes, achieving a surface roughness of 1.032&#xa0;nm. Additionally, the CMP process adheres to environmental protection standards, making it a promising approach for advanced material processing applications in the future.</p>