Integrated framework for designing durable green corrosion inhibitors from Spirulina: Cultivation, extraction, and electrochemical evaluation.

This study presents a comprehensive framework for designing eco-friendly corrosion inhibitors from Spirulina platensis. Biomass production was optimized for yield and quality, followed by selective extraction using ultrasound-assisted and orbital-shaking methods applied to wet and dry biomass. Extracts were chemically characterized and tested via potentiodynamic polarization and electrochemical impedance spectroscopy. The dry-biomass ultrasound-assisted extract (D1) showed the highest inhibition efficiency (90%-92%) and achieved a corrosion rate of ∼ 1.41 mm year - 1 at 1,000 ppm, maintaining ∼ 77% efficiency over 72 h. Statistical analysis confirmed that the presence of Spirulina extracts significantly improved corrosion resistance, with extract type, concentration, and immersion time identified as key variables. This work validates the potential of microalgal formulations as effective green inhibitors and offers a reproducible methodology for the long-term evaluation of bio-based corrosion protection strategies relevant to sustainable materials engineering.