The Role of Cassava Leaf Extract as Green Inhibitor for Controlling Corrosion and Scale Problems in Cooling Water Systems

The addition of synthetic corrosion and scale inhibitors in a recirculating cooling water system is a well-known method to defeat corrosion and scale problems. In this work, we utilize the extract from cassava leaf, which is agricultural waste in Thailand as a green inhibitor. Corrosion inhibition efficiency with using cassava leaf extract (CLE) for mild carbon steel was investigated in a simulated cooling water solution under both stagnant and hydrodynamic conditions. A mock-up of a recirculating cooling water system was custom-built to imitate the hydrodynamic conditions used in industry. Effects of CLE concentration (0, 50, 100, 200, 400, 600, and 800 ppm) and temperature (35 °C, 45 °C, and 55 °C) on corrosion inhibition efficiency were investigated. Increasing the CLE concentration increased its inhibition efficiency. In the case of stagnant conditions, the CLE showed a corrosion inhibition efficiency of 97.4% with 800 ppm CLE at 35 °C. The CLE performed as an anodic inhibitor. A decrease in inhibition efficiency was observed when the temperature was increased. For the hydrodynamic conditions with a flow rate of 34 L min−1 at 55 °C, a corrosion inhibition efficiency of 75.7% was seen with 200 ppm CLE. A scale inhibition efficiency of the CLE was investigated at concentrations of 0, 200, 800, and 2000 ppm. A 76.1% CaCO3 scale inhibition efficiency was obtained with 2000 ppm CLE. A change in the CaCO3 morphology due to the adsorption of the CLE inhibited scale formation.