Superhydrophobic films from waste polypropylene for corrosion protection of carbon steel in 3.5 % sodium chloride solution

The corrosion inhibition capabilities of polymer-based coatings are often limited by their reliance on additives, chemicals, and complex fabrication methods. In this study, we repurpose waste polypropylene (PP) into functional films using a tandem dissolution and spin-casting process, enabling direct application onto metal surfaces for enhanced corrosion resistance. This method eliminates the need for chemical grafting or nanofiller incorporation, offering a simpler and more sustainable route to surface protection. The resulting films exhibit a maximum water contact angle (CA) of 157°, indicating superhydrophobic behavior. Electrochemical impedance spectroscopy (EIS) measurements show a marked improvement in charge transfer resistance (R_ct), increasing from 184 Ω·cm² for bare carbon steel to 16,000 Ω·cm² for the PP-coated surface. By utilizing plastic waste as a feedstock, this approach presents an environmentally responsible and cost-effective alternative to conventional polymer-based corrosion inhibitors.