Natural Resin-Based Anticorrosive Coatings from Rosin and Croton lechleri for Metallic Surface Protection

Corrosion of metallic materials in aggressive environments remains a major challenge affecting the durability of industrial structures and equipment. In this context, protective coatings based on natural materials have attracted increasing attention as sustainable alternatives to conventional anticorrosive systems. This study evaluated the physicochemical, thermal, and anticorrosive properties of rosin-based coatings modified with Dragon's Blood (Croton lechleri). Formulations containing 0.5 wt.% and 1.0 wt.% of the natural resin were applied to carbon steel and aluminum substrates. The developed coatings were characterized by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), while their anticorrosive performance was evaluated using an accelerated direct-current corrosion test in seawater for 60 min and seawater immersion tests for 30 days. Mass loss measurements, together with ANOVA and Tukey's multiple comparison tests, were used to compare the protective performance of the different formulations. FTIR analysis suggested that the incorporation of Dragon's Blood did not significantly modify the chemical structure of the rosin matrix, whereas TGA and DSC confirmed adequate thermal stability of the developed coatings. The formulation containing 0.5 wt.% Dragon's Blood consistently exhibited the lowest mass loss for both carbon steel and aluminum, corresponding to reductions of approximately 55.1% and 73.2%, respectively, compared with the uncoated controls after 30 days of seawater immersion. Both the 30-day seawater immersion test and the accelerated direct-current corrosion test consistently identified the formulation containing 0.5 wt.% Dragon's Blood as the most effective coating system. These findings demonstrate that Dragon's Blood is a promising sustainable bio-based additive capable of enhancing the barrier properties and anticorrosive performance of rosin-based coatings for metallic substrates exposed to marine environments.