A new experimental approach to chemical ageing in materials and piping for drinking water infrastructure exposed to chlorine dioxide

The long-term durability of polyethylene (PE) pipes in water distribution networks is gaining importance due to updated European regulations on drinking water safety. This study investigates the accelerated ageing of two PE grades (PE1 and PE2) exposed to chlorine dioxide (ClO₂), a disinfectant known for its high efficacy and minimal formation of harmful by-products. Pilot-scale tests were conducted under realistic and dynamic conditions to evaluate chemical, microstructural, thermal, and mechanical degradation. The experimental approach introduces a novel preliminary ageing protocol, integrating both micro- and macro-scale characterization of materials exposed to ClO₂. Physicochemical analyses revealed a significant increase in the carbonyl index, particularly in PE1, which exhibited a higher oxidation rate (0.287 CI/CI₀/day) compared to PE2 (0.216 CI/CI₀/day). Crystallinity also increased by approximately + 4 % in PE1 and + 2 % in PE2. These changes were accompanied by a progressive decline in mechanical performance: between weeks 6 and 13, reductions in elongation at yield and ductility were observed. From week 12 onward, both materials failed to meet the mechanical conformity threshold defined by EN 12201-2:2024, with elongation at break falling below 350 %. Based on degradation kinetics, the estimated service life under real operating conditions was 18 years for PE1 and 23 years for PE2 at 40°C. The durability of PE1 and PE2 ranges from 19 to 60 years, depending on ClO₂ levels and temperature.