Bio-based polyurethanes (PU) prepared through green routes using technical cashew nut shell liquid (TechCNSL) for anti-corrosive application could protect infrastructures and addresses environmental concerns. The synthesis was carried out in situ by an acid-catalyzed condensation reaction of TechCNSL and formaldehyde (F) at 120 °, C. The final structure was obtained through addition polymerization of TechCNSL-F with toluene diisocyanate (TDI) at room temperature (OH: NCO ratios: 1: 0. 8, 1: 1 and 1: 1. 2) to form TechCNSL-F-PU. The characteristic properties of the coatings were influenced as a function of free –, OH and –, NCO groups that is influenced by the composition of TechCNSL used. The high coating resistance (Rc) and change in solution resistance (Rs) values along with lower coating capacitance (Cc) values supporting sufficient protection ability and compactness to the metallic substrate was determined by non-destructive electrochemical impedance spectroscopy (EIS) studies. Structural and progress of the reaction was evaluated by ATR/FTIR, whereas XRD revealed the amorphous nature of the hydrophobic films/coatings with a contact angle of 100°,for TechCNSL-F-PU1: 1. The variation in thermal stability with TDI concentration and glass transition (Tg) temperature was based on the degree of cross-linking density of the systems. The degree of cross-linking was calculated through estimation of gel content, which varied from 96 to 98% based on the concentration of TDI with thermal stability by max 265 °, C. TechCNSL-F-PU1: 1 shows excellent films/coatings adhesion, anticorrosion performance, chemical and mechanical resistance in the various chemical environment (water, 3. 5% of HCl, NaCl and NaOH) and showed the best performance. These thermally stable and mechanically robust PU films/coatings can be projected for the corrosion protective applications.