Synthesis and characterization of hydrophobic SiO2-MnO2/PE coatings reinforced with stearic acid for corrosion mitigation

• The hydrothermal processing temperature significantly affects the contact angle of the coating, influencing its hydrophobic properties. • The immersion duration in stearic acid impacts the contact angle of the SiO2-MnO2 coating, optimizing its surface performance. • Prolonged immersion duration also influences the rate of contact angle degradation, providing insights into the coating's long-term stability. • The composite structure of SiO2-MnO2 enhances the uniformity and durability of the hydrophobic layer, ensuring better performance in corrosion resistanc Corrosion, a significant industrial issue causing material and economic losses, can be mitigated by hydrophobic coatings. This study develops a SiO₂-MnO₂/Polyethylene (PE) coating reinforced with stearic acid to enhance corrosion resistance, synthesized via a one-step hydrothermal method at 110–140°C. The coating was immersed in stearic acid for 0.5, 1, and 5 min to optimize hydrophobicity and durability. Characterization involved X-Ray Diffraction (XRD) for crystal structure, Scanning Electron Microscopy (SEM) for morphology, and Fourier Transform Infrared Spectroscopy (FTIR) for functional groups, with contact angles measured by DSLR camera and corrosion tested in 1% NaCl. Decay rate (k) was monitored over 7 days, and corrosion rate determined via weight loss. Without stearic acid, the coating achieved a contact angle of 138.4° at 130°C. Post-reinforcement, the 1-min immersion at 130°C peaked at 141.15° but exhibited the highest decay rate (0.022 °/day) and a corrosion rate of 0.16 mm/year, indicating strong initial hydrophobicity but rapid degradation. Conversely, the 5-min immersion yielded the lowest decay rate (0.019 °/day) and corrosion rate (0.11 mm/year), reflecting superior stability and protection from a thicker, aggregated structure, despite a 133.4° contact angle. The 0.5-min sample showed intermediate results (0.020 °/day, 0.18 mm/year). Unlike prior studies prioritizing initial hydrophobicity, this work highlights the role of coating thickness, stability, and synthesis conditions in achieving long-term corrosion resistance, providing novel insights for industrial applications.