Theoretical Research On PAA And PEI In Metal Protection

Metals and their al oys are widely used in aerospace,transportation and chemica l industries.Their corrosion can cause huge economic losses and environmental pollut io n.Efficient metal protection method is the basis of its wide application,and it has received extensive attention in the industrial and scientific fields.In recent years,self-repair ing protective film has attracted great attention in the field of metal protection due to its excel ent corrosion resistance,durability and self-healing.A large number of experimental studies have been carried out on the modification,development and mechanism of the new self-healing membrane,but the growth and repair process of the self-healing film is not clear.Although it is difficult to study the transient process in the experiment,and the theoretical simulation method can directly observe the process in the atomic level,which has a certain of advantages in this research.In this paper,aluminum is used as the substrate,PAA,PEI and the self-healing film composed of PAA and PEI are the research object.The corrosion inhibition and selfrepairing films of PAA and PEI on aluminum metal surface were studied theoretically by using the Bottom-up research route through and theoretical research methods in differe nt levels.The details of the work are as follows:Firstly,the quantum chemical calculation method was curried to study the influe nce of the electronic structure properties of PAA and PEI on the corrosion inhibit io n performance.It is found that PEI has lower ?E,? and ? values,and higher ?,? and ?N values than PAA,which indicates that PEI has better corrosion inhibition performance.The calculation results of protonated PEI molecules show that the corrosion inhibit io n efficiency increases with the decrease of PH while the chain length has little effect on the electronic properties of the corrosion inhibitor.Secondly,molecular dynamics was used to simulate the adsorption of a single PEI molecule on the hydroxylated Al(111)surface,and then the film formation process of PEI molecular solution on the Al(111)surface was further simulated by coarse-granulat io n.Studies have shown that PEI molecules can spontaneously adsorbed on the metal surface at room temperature and play a role in corrosion inhibition,which are consistent with the experimental report trend.Finally,the coarse-grained model and parameters of PAA and PEI in Al substrate and complex solution environment were constructed and verified.On this basis,the growth mechanism,damage repair mechanism and influencing factors of PAA and PEI self-healing film were studied.The results show that PAA and PEI molecules will gradually mix with diffusion in the layer-by-layer self-assembled film.The damage of the film layer on the surface of the substrate is repaired by the selective adsorption of metal to PEI,and the self-healing of the upper hybrid film is achieved by the diffusion of PAA and PEI.The diffusion of polyelectrolyte plays a major role in the self-assembly and selfrepair of the membrane.Studies on the factors influencing membrane growth show that the fluidity of the membrane increases with the degree of ionization of polyelectrolytes increases,but the fluidity of the membrane decreases with the increase of the degree of polymerization.Studies on the factors influencing membrane properties show that the fluidity of the membrane decreases,and the speed of damage repair slows down with the degree of ionization of polyelectrolytes increases.In addition,the stability of the membrane increases,the fluidity decreases,and the damage repair speed slows down with the increase of the degree of polyelectrolyte polymerization.