Investigation of sol-gel derived organic inorganic hybrid coatings based on commercial epoxy resin for improved corrosion resistance of 304 stainless steel

In this study, a commercial epoxy resin (KER 828) was employed as the organic component of the organic inorganic hybrid coating to enhance corrosion resistance while reducing production costs via the sol-gel method. Hybrid coatings were formulated with varying weight percentages and subsequently applied to 304 stainless steel substrates to assess their effectiveness against corrosion. The Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), pull off test and water contact angle (WCA) techniques were employed to characterize the obtained coatings. The corrosion behavior of both the uncoated stainless steel and the coated samples was evaluated through Potentiodynamic Polarization test. Additionally, the electrochemical impedance spectroscopy (EIS) analysis was employed over time intervals of 1 h, 1 day, 1 week and 1 month exposure to 3.5 wt% NaCl solution. The results demonstrated that coatings with equal weight percentages of the organic and inorganic phases (1:1:1) exhibited the highest corrosion resistance, which can be attributed to the enhanced Si-O-Si network formation. Then SiO₂ nanoparticles were incorporated into the optimal coating formulation to examine the barrier effect and the impact of nanoparticles presence on the hybrid coating performance (1:1:1:0.01). The results acquired from Potentiodynamic polarization (E_corr of - 0.327 V and i_corr of 9.83 × 10^-11 A.cm^-2), EIS (R_ct of 158320 Ω.cm² after 1 month of immersion) and WCA (81.67°) analysis indicated that coating containing SiO₂ nanoparticles (1:1:1:0.01) provided superior surface protection compared to all other synthesized hybrid coatings.