Synthesis And Corrosion Inhibition Properties Of Polyaspartic Acid Deriverives

Mild steel equipment is susceptible to severe corrosion during descaling,pickling,etc.,and causes equipment damage,economic losses,and even production accidents.The use of corrosion inhibitor is the most economical and effective way to improve the corrosion resistance of carbon steel materials.Green corrosion inhibitors have attracted much attention with the improvement of people's awareness of environmental protection.Polyaspartic acid?PASP?is a non-toxic,biodegradable and environmentally friendly polymer,but its corrosion inhibition performance for mild steel in acidic media is poor.In this paper,a series of polyaspartic acid derivatives were prepared by introducing new functional groups into PASP molecular chain.The corrosion inhibition properties of these derivatives for 20^#mild steel in 0.5 M H₂SO₄ were studied by weight loss,electrochemical method,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,adsorption thermodynamics and theoretical calculation.The main research work and results are as follows:1.Six polyaspartic acid derivatives containing functional groups were synthesized by the reaction of aminopropylimidazole,alkylamine,phenylethylamine,dopamine and cysteamine with polysuccinimide.Compared with PASP,the corrosion inhibition efficiencies of these derivatives for 20^#mild steel in 0.5 M H₂SO₄ solution were improved with varying degrees.Taking potentiodynamic polarization test results as an example,the corrosion inhibition efficiency of the synthesized polyaspartic acid derivatives on mild steel is close to or over 90%at 100 mg L^-1,while the inhibition efficiency of PASP under the same conditions is only 71.8%.2.Adsorption thermodynamic studies show that the adsorption of polyaspartic acid and its derivatives on mild steel surface includes both physical and chemical adsorption.The Gibbs free energy of the adsorption process of polyaspartic acid derivatives is smaller and the adsorption equilibrium constant is larger,which indicates that the derivatives with various functional groups have stronger adsorption capacity on mild steel surface.Analyzing the functional groups in polyaspartic acid derivatives,we can find that the?bonds in imidazole,phenylethylamine and dopamine,the lone pair electrons of sulfur in sulfhydryl group can interact strongly with the d orbital of iron atom space.These forces lead to the enhancement of the adsorption capacity of polyaspartic acid derivatives on the surface of mild steel.Thus,the corrosion of corrosive medium to metal is weakened.In addition,the introduction of alkyl chain can form a hydrophobic layer on the surface of mild steel and the contact between corrosive medium and metal is prevented,which also plays an important role in improving the performance of corrosion inhibitors.3.XPS analysis on the surface of mild steel shows that polyaspartic acid derivatives can form an adsorption layer on the surface of mild steel.SEM analysis also shows that the corrosion of the mild steel surface were significantly retarded under the protection of polyaspartic acid derivatives.4.The theoretical parameters of corrosion inhibitors were calculated by density functional theory,and the potential corrosion inhibition properties of polyaspartic acid and its derivatives were analyzed from a theoretical perspective.It was found that the modified polyaspartic acid has a smaller band gap energy,and it is easier to provide electrons to the surface of the carbon steel,so that a better protective film can be formed on the surface of the carbon steel.