Development and Performance Evaluation of Novel Chestnut Tannin-Based Waterborne Anti-Corrosion Coatings for Aluminum

Abstract

The increasing demand for sustainable corrosion protection methods has driven the replacement of toxic pigments in coatings. This study investigates the potential of chestnut tannin as an eco-friendly alternative to commercial phosphates for enhancing the anticorrosive properties of waterborne epoxy and acrylic coatings on AA1050 aluminum. Electrochemical evaluations performed in 0.1 M NaCl solution revealed that chestnut tannin acts as a mixed-type corrosion inhibitor, effectively suppressing both cathodic and anodic reactions, comparable to second and third-generation phosphates (Nubirox 106 and K-White 105). Coated panels were subjected to electrochemical impedance spectroscopy (EIS) and accelerated corrosion tests (humidity and salt spray chambers). All coatings demonstrated excellent adhesion. Both tannin-based (E-CAS) and phosphate-based (E-NUB) epoxy coatings exhibited premature blistering in the humidity chamber, likely due to intrinsic film characteristics, although they showed acceptable substrate protection. In contrast, acrylic coatings (A-CAS and A-KW) exhibited superior performance, with no blistering in the humidity chamber and strong active corrosion protection in salt spray, particularly A-KW.SEM-EDS analysis confirmed reduced corrosion product formation and effective chloride suppression on inhibited substrates. Overall, chestnut tannin demonstrated competitive anticorrosive performance within both coating matrices, highlighting its promise as a sustainable pigment for aluminum protection.