Turnip peel extract as green corrosion bio-inhibitor for copper in 3.5% NaCl solution

In this study, for the first time, we report turnip peel extract (TPE) as an eco-friendly, inexpensive vegetable waste and green bio-inhibitor for copper corrosion in 3.5 wt% NaCl solution. Ultrasound-assisted water extraction was used to prepare the TPE, and this method allows us to naturally and directly use this substance as a green inhibitor in corrosive media. GC-MS analysis was utilized to detect the main chemical compounds of TPE. EIS tests and potentiodynamic polarization techniques were used to determine the resistance of copper against corrosion in 3.5 wt% NaCl solution. SEM-EDS analysis was utilized to analyze the surface morphology and elemental identification of the copper surface. It was found that by the increment of the amount of TPE, the inhibition efficiency (IE) increased, the maximum IE was almost 92% which is promising. Also, the inhibition efficiency of TPE was studied in different corrosive solution temperatures (298-338 K) that showed the increment of temperature, reduces the inhibition efficiency, although IE is almost 64% at 338 K which is acceptable. The adsorption mechanism of TPE molecules on the copper surface is considered as physical adsorption due to the positive value of AH and adsorption isotherm which was matched with the Langmuir isotherm model.