Sunflower stalk extract as a novel green inhibitor on aluminium corrosion in HCl solution

Utilization of sunflower stalks to develop green and efficient corrosion inhibitors can further improve the added economic value of sunflower. In this work, sunflower (Helianthus annuus.) stalks extract (HASE) was prepared for the first time by ultrasonic extraction method. To investigate the inhibition effectiveness and mechanism of HASE on aluminium in HCl media, a variety of experimental techniques including weight loss, electrochemical tests and surface characterizations were utilized. The findings show that in 1.0 M HCl solution at 20 degrees C, 500 mg L-1 HASE has an inhibitory effectiveness of up to 93.3 %. HASE adsorption adheres to Langmuir isotherm model, which contains both chemisorption and physisorption in its adsorption behaviour on aluminium surface. HASE is a cathodic inhibitor that primarily slows down the cathodic hydrogen precipitation process. HASE greatly lowers the double layer capacitance and dramatically raising charge transfer resistance. The inhibitory action of HASE on aluminium in HCl medium is confirmed by corrosive solution testing and metal surface characterizations, which also provides evidence of inhibitor molecular adsorption.