<![CDATA[This study aimed to evaluate the effectiveness of a castor oil and nano-silica based multilayer coating system in improving the corrosion protection of ASTM A36 in chloride-rich environments. ASTM A36 specimens were prepared and coated in four configurations: uncoated steel, epoxy-coated steel, castor oil/nano-silica-coated steel, and a multilayer system consisting of castor oil, nano-silica, and epoxy. The primer was formulated by dispersing 5 wt% nano-silica in castor oil with Triton X-100 as surfactant, followed by epoxy topcoat application and controlled curing. The coating systems were characterized using Fourier Transform Infrared Spectroscopy to identify functional group interactions, coating thickness measurements, potentiodynamic polarization for corrosion rate determination, immersion mass-loss testing for 21 days, and visual degradation observation. The results showed that the addition of nano-silica and epoxy altered the chemical structure of the coating and promoted a denser barrier network. Electrochemical testing indicated a substantial reduction in corrosion rate for coated specimens compared with uncoated steel, while thickness analysis showed that the multilayer coating produced the highest thickness and best uniformity. Immersion and physical degradation observations further confirmed that the integrated coating system improved barrier integrity and reduced corrosion damage. These findings indicate that combining castor oil, nano-silica, and epoxy is a promising strategy for developing durable and environmentally compatible anticorrosion coatings for structural steel.]]>
