Preparation And Corrosion Inhibition Of Modified Chitosan Composites

The environmental pollution caused by the corrosion of metal,the loss of people's lives and property and the economic loss are too numerous to be enumerate every year.It is an urgent to study and develop green anti-corrosion materials with high efficiency and no ecological harm.Among many anticorrosive materials,inhibitors have been widely applied in many anticorrosion fields due to their advantages such as high efficiency,low cost,wide application and simple technology.The early inhibitors were mainly inorganic compounds,but the use of its caused serious damage to the environment.Therefore,the biodegradable and harmless organic compounds have become research hotspot.Chitosan,as the most abundant natural polymer at present,has been regarded as a potential green corrosion inhibitor by virtue of its large number of free amino and hydroxyl groups,and biodegradable and environment-friendly characteristic.In this paper,according to the molecular structure of chitosan,chitosan modified with salicylaldehyde and polyaniline,through the study of preparation conditions and optimization of modified chitosan composite,a corrosion inhibitor with good corrosion inhibition performance is obtained.The corrosion inhibition properties of chitosan composites were studied by weight-loss method,electrochemical test method,corrosion morphology analysis and quantum chemistry calculation.At the same time,by corrosion morphology analysis and quantum chemical calculation of chitosan composites to analyze the inhibition mechanism and reveal the role of corrosion inhibitor on the metal surface.The main results of the study are as follows:?1?Salicylaldehyde modified chitosan corrosion inhibitor was prepared with salicylaldehyde as modifier.The effects of the mass ratio of salicylaldehyde to chitosan and the reaction temperature on the corrosion inhibition performance of Q235 carbon steel were studied emphatically.The experimental results showed that the mass ratio of chitosan to salicylaldehyde was 6:1,the reaction temperature was 60oC,the salicylaldehyde modified chitosan corrosion inhibitor prepared in 1.0 M HCl medium has the worst corrosion effect to Q235 carbon steel,the corrosion inhibition rate can reach 83.77%.At the same time,the corrosion inhibition properties of corrosion inhibitor under different corrosion inhibitor concentration and corrosion temperature conditions were studied by weight loss method.The results showed that the adsorption of salicylaldehyde modified chitosan corrosion inhibitor on metal surface accords with Langmuir isothermal model,spontaneously adsorbs on the surface of Q235 carbon steel,and the obtained thermodynamic parameter|?G_ads|was about 40KJ?mol^-1,indicating that the salicylaldehyde modified chitosan molecule mainly acts on the surface of carbon steel by chemical adsorption and physical adsorption of the common role.In addition,the use of electrochemical test method,salicylaldehyde modified chitosan corrosion inhibitor is a mainly to inhibit the cathode-based mixed-type corrosion inhibitor.?2?Aniline as raw material,the use of chemical oxidation polymerization,ammonium persulfate as initiator,acetic acid and sulfamic acid as a composite doping acid,preparation of polyaniline/Chitosan composite inhibitor.The effects of the mass ratio of aniline to chitosan and the molar ratio of aniline to ammonium persulfate on the corrosion resistance of Q235carbon steel were investigated emphatically.The experimental results showed that the optimal conditions were aniline and chitosan mass ratio of 6:1,and ammonium persulfate molar ratio of 12:10,the resulting polyaniline/chitosan composite corrosion inhibitor at 1.0 M HCl medium has the best corrosion resistance to Q235 carbon steel.The structure of the corrosion inhibitor was analyzed by FT-IR.Electrochemical tests showed that:polyaniline/chitosan composite was a mainly inhibit the cathode-based mixed inhibitor.When the dosage of corrosion inhibitor was 200 ppm,the inhibition rate can reach the maximum value.The adsorption of corrosion inhibitor on the metal surface conforms to the Langmuir isothermal model.From the thermodynamic point of view,this was the behavior of the inhibitor molecules spontaneously adsorbed on the surface of Q235 carbon steel.In addition,quantum chemical theory was used to investigate the corrosion inhibition mechanism of the corrosion inhibitor.The chemical active sites of the polyaniline/chitosan complex were inferred to be elements or groups containing lone pairs of electrons on the glycosidic ring in the polyaniline/chitosan complex,which can form coordinate bonds with the empty d orbitals on the Fe atom in Q235 carbon steel and also chelate with Fe²⁺and Fe³⁺,which made the Q235 carbon steel form a better corrosion protection film.?3?Using salicylaldehyde and polyaniline as modifiers,chemical oxidation polymerization,ammonium persulfate as initiator,and acetic acid and sulfamic acid as compound doping acid were studied to prepare polyaniline/salicylaldehyde chitosan complex corrosion inhibitor.The structure of the corrosion inhibitor was analyzed by FT-IR.Electrochemical tests showed that polyaniline/salicylaldehyde modified chitosan mainly inhibits cathode-based mixed corrosion inhibitor.When the addition amount of polyaniline/salicylaldehyde modified chitosan complex was 300 ppm,the inhibition rate reached the maximum value of 82.62%.Quantum chemical calculations were used to deduce the chemical active sites of the polyaniline/salicylaldehyde modified chitosan complex.The lone pairs of electrons provided by the benzene ring,C=N and N atoms can directly form the coordination bond with the empty orbit on the metal element,chelating with Fe²⁺and Fe³⁺,forming a complete adsorption film on the surface of carbon steel to protect the Q235 carbon steel from being attacked by HCl.