Green synthesis of biomass-derived carbon dots as an efficient corrosion inhibitor

Metallic corrosion threatens the safety and reliability of metallic facilities and equipment, and exacerbates the issues of environmental pollution and economic losses. However, it is still a challenge to obtain green inhibitors employing sustainably renewable and economical materials. Herein, biomass-derived carbon dots (CDs) are prepared via green hydrothermal treatment only using lichi leaves as the raw material, and their corrosion inhibition properties for Q235 carbon steel in 1 M HCl are systematically investigated using weight loss test, electrochemical impedance spectra (EIS) and potentiodynamic polarization (PDP) measurement for the first time. Specifically, the as-obtained eco-friendly lichi leaves-derived CDs (LCDs) possess numerous O- and N-containing functional groups. And these groups endow LCDs almost unchanged intensities of photoluminescence (PL) and ultraviolet–visible (UV–vis) peaks for two weeks in 1 M HCl solution, demonstrating a long-term dispersion stability of LCDs. On the premise, LCDs at only 200 mg/L concentration reveal an eminent corrosion inhibition ability with a high inhibition efficiency of 98.06% for Q235 carbon steel immersed in 1 M HCl. Meanwhile, they enable the surface roughness (Sa) value of steel surface to starkly reduce by 73.7% (from 12.428 to 3.264 μm) by comparison with that of blank HCl solution. Furthermore, based on analyses of adsorption isotherm and corrosion morphology, their inhibition mechanism is attributed to the protective film formed by LCDs chemical and physical adsorptions. This work firstly substantiates the remarkable inhibition capacities of biomass-derived CDs and provides their green synthesis approach, beneficial to stimulate the advancement of green and efficient corrosion inhibitors.