Polyester-based geosynthetics are widely employed in civil engineering applications owing to their high mechanical performance and cost-effectiveness. However, exposure to aggressive alkaline environments, such as high-pH soils and groundwater, significantly reduces their long-term durability. In this study, polyvinyl alcohol (PVA) was employed as a coating material for polyester yarns due to its intrinsic alkaline resistance and water solubility, reducing the need for organic solvents and enhancing environmental sustainability. To improve water resistance and mechanical stability, PVA was crosslinked using crosslinkers,. The crosslinked coating was applied to polyester yarns via a padding mangle machine and dried under controlled conditions. The resulting materials demonstrated excellent alkali resistance up to pH 12.5 at 50°C, with negligible physical changes after prolonged exposure. Gravimetric analyses, including GSM determination, confirmed uniform coating deposition and mechanical reinforcement. This work provides a cost-effective, scalable, and environmentally sustainable strategy to extend the functional lifespan of polyester geosynthetics in harsh environments.