Corrosion Inhibition Performance Of Self-assembled Films Of Two Green Corrosion Inhibitors For Copper In 0.5M H₂SO₄ Solution

In recent years,corrosion inhibitor technology has been widely used in chemical production,petrochemical,chemical cleaning and other fields where metal corrosion protection is required due to its simple equipment,convenient operation and high economic benefits.However,some corrosion inhibitors reported in the literature are highly toxic and can cause severe environmental pollution.With the proposing of green chemistry and the strengthening of environmental awareness,the development and exploration of efficient and green corrosion inhibitors has become an important issue.In this paper,the T.E.S.T software based on QSAR theory was used to calculate the toxicity of hundreds of representative corrosion inhibitors reported in the past ten years.Two organic compounds,namely zinc dibenzyldithiocarbamate?ZBEC?and dibenzothiazyl disulfide?DM?were finally selected as green corrosion inhibitors.ZBEC and DM molecules were assembled on the surface of metallic copper by self-assembly technique.The corrosion inhibition performances of ZBEC and DM self-assembly films for copper in 0.5 M H₂SO₄ sulfuric acid solution were investigated by electrochemical experiments,surface analysis,quantum chemistry and molecular dynamics simulation.The research results were listed as follows:?1?T.E.S.T software was used to calculate the toxicity of nearly one hundred corrosion inhibitors reported in literatures.The types of these corrosion inhibitors include thiazoles,imidazoles,pyridines,thiols,triazoles,acids,quinolines and organic heterocycles.Mutagenic?M??Developmental toxicity?D??Mouse oral LD50 and Daphnia magna LC₅₀?48hr?are four predicted toxicity endpoints.The calculation results showed that the type and quantity of functional groups and molecular structure have influences on the toxicity level of the substance.Two organic compounds?ZBEC and DM?were selected as green corrosion inhibitors;?2?The results of FT-IR,contact angle and ellipsometry indicated that ZBEC and DM molecules were successfully assembled on the copper surface to form hydrophobic self-assembled films,and the hydrophobicity of ZBEC self-assembled film was better than that of DM.The adsorption of ZBEC and DM on the copper surface obeyed the Langmuir adsorption model,and the adsorption type changed from mixed adsorption to total chemical adsorption with the extension of self-assembly time;?3?When the ZBEC concentration was 0.008 M and the self-assembly time was 30min,the corrosion inhibition efficiency of ZBEC self-assembled film for copper in 0.5M H₂SO₄ solution reached 99.71%.While the DM concentration was 0.008 M,the self-assembly time was 12 h,the corrosion inhibition efficiency of DM self-assembled film for copper in 0.5 M H₂SO₄ solution reached 99.01%;?4?The results of potentiodynamic polarization curves showed that the self-assembled films of ZBEC and DM molecules did not change the corrosion reaction mechanism of copper,but only inhibited the anodic dissolution and cathode oxygen reduction reaction of copper by covering the surface active sites;?5?Quantum chemistry and molecular dynamics simulations have studied the corrosion inhibition mechanisms of ZBEC and DM molecules on copper surface.It is found that ZBEC had more adsorption active sites than DM,and its energy gap and binding energy were also smaller than those of DM molecules.Hence,the assembly of ZBEC molecule on the copper surface is more efficient than the DM molecule,and it's corrosion inhibition efficiency is also higher than the DM molecule.