Estudo da eficiência do líquido da casca da castanha de caju como inibidor verde de corrosão em aço baixo carbono

Abstract

Metal corrosion causes significant economic losses, with classical estimates indicating values between 3–4% of the GDP of several countries, and drives the demand for sustainable solutions. This study evaluates the feasibility of cashew nut shell liquid (CNSL) as a “green” alternative for anticorrosive protection applied to ASTM A36 steel. Five surface conditioning systems were compared: L (anticorrosive primer formulated with CNSL), C (commercial paint), Z (zinc-rich paint), G (galvanization), and S (unprotected), immersed in saline solution (0.6 mol/L NaCl) for 24, 72, and 168 h. The evaluation comprised visual inspection and complementary techniques (optical microscopy/ImageJ, pencil hardness, surface roughness, UV–Vis spectroscopy, and XRF). Robust initial performance was observed for galvanization up to 72 h, followed by pronounced degradation at 168 h. The CNSL-based coating exhibited moderate integrity in the short term, acting predominantly as a barrier-type coating, reducing the contact between the metallic substrate and the electrolyte. UV–Vis curves showed increased absorbance over time for L, C, Z, and especially S, indicating intensified leaching and formation of corrosion products, more pronounced in the absence of protection. It is concluded that CNSL, in the formulation studied, presents technical potential as a component of barrier-based anticorrosive systems, particularly for shortto medium-term exposures, combining environmental appeal with performance superior to that of the commercial paint evaluated. Optimization of formulation and film thickness, as well as the expansion of electrochemical testing, is recommended to consolidate its application at the industrial scale.