Corrosion Inhibition Of A New Type Of Nitrogen-doped Carbon Dots For Carbon Steel In Hydrochloric Acid Solution

In order to suppress the corrosion in the picking process of metal materials,nitrogen-doped carbon dots（NCDs）with a size of 2～4 nm have been synthesized via hydrothermal synthesis with citric acid and thiourea as precursors.The corrosion inhibition behavior of NCDs on X80 carbon steel were investigated in 0.1 M HCl solutions with electrochemical experiments,the weight loss method,surface analysis,and adsorption isotherm curve.The results of weight loss experiment and electrochemical experiment show that NCDs can effectively inhibit the corrosion of X80 carbon steel in 0.1 M HCl solution,and the inhibition efficiency increases with the increase of the concentration of NCDs.At 298 K,when the concentration of NCDs is 10 mg/L,the maximum inhibition efficiency can reach 92.98%.The adsorption of NCDs on X80 carbon steel is physicochemical adsorption,satisfying the Langmuir adsorption isotherm.The results of Tafel curve show that NCDs is a mixed inhibitor mainly composed of inhibition cathodes.EIS data show that as the concentration of NCDs increases,the diameter of capacitive reactance increases and more corrosion inhibitor molecules can be adsorbed on the metal surface than water molecules,enhancing the corrosion resistance of carbon steel.The SEM figure shows that NCDs can effectively inhibit the corrosion of carbon steel in HCl solution.Weight loss experiment and surface morphology strongly confirm the results of electrochemical experiments.Finally,molecular dynamics（MD）and quantum chemical calculation is used to theoretically study NCDs.The adsorption configuration and binding energy of NCDs on Fe（110）surface is obtained by molecular dynamics calculation.The parameters(the highest occupied molecular orbital energy E_HOMO,lowest unoccuated molecular orbital energy E_LUMO,energy gapΔE,dipole momentμ,hardnessη,flexibilityσ,electron transfer numberΔN,electrophilic indexω)and molecular orbital distribution diagram of frontier orbital are obtained by quantum chemistry.Molecular dynamics calculations show that NCDs is adsorbed parallel to Fe（110）,and the binding energy of NCDs is higher than that of citric acid.Related parameters obtained by quantum chemistry further confirmed the corrosion inhibition performance of NCDs,and the front orbital molecular distribution map predicted the adsorption center of NCDs on metal surface.