Aquatic Functional Products

Wardah Maulida Saldi, Erna Hastuti

Corrosion of carbon steel in chloride-rich environments remains a critical challenge, while conventional chitosan-based coatings often suffer from limited barrier integrity and durability. This study addresses this limitation by developing an eco-friendly chitosan–silica composite coating derived from crab shell waste and systematically evaluating the effect of silica loading (1–4%) on the corrosion protection of ASTM A36 steel under 10% NaCl immersion. Chemical interactions were examined using Fourier-transform infrared spectroscopy (FTIR), while corrosion performance was assessed through weight loss measurements, electrochemical impedance spectroscopy (EIS), and surface morphology observations. FTIR results confirmed the successful incorporation of silica and enhanced hydrogen bonding between silanol groups and chitosan chains. The composite coating containing 2% silica exhibited the highest corrosion resistance, achieving the lowest corrosion rate and the highest polarization resistance compared to pure chitosan and uncoated steel. The improved performance is attributed to enhanced barrier properties of the chitosan–silica composite, where the presence of well-dispersed silica particles limits chloride ion penetration. At higher silica loadings, corrosion protection declined, likely due to reduced coating uniformity. These findings demonstrate that controlled silica reinforcement introduces a distinct corrosion protection mechanism beyond conventional chitosan coatings and highlight the potential of bio-based hybrid coatings for sustainable steel protection.