Study On Corrosion Inhibitor Mechanism Of Chito-oligosaccharides In CMP Of Stainless Steel

Because of its excellent characteristics,stainless steel substrates have gradually become one of the most important materials for flexible electronic product substrates.For the surface roughness and surface flatness required by substrate materials,chemical mechanical polishing is presently a significant technique to acquire ultra-precision surface processing.As a corrosion inhibitor that can effectively improve the surface quality after polishing,it is one of the important components of polishing fluid.At present,the corrosion inhibitors commonly used in stainless steel CMP process mainly include benzotriazole,etc.,but this kind of corrosion inhibitor has the disadvantages of being difficult to hydrolyze and high toxicity.The corrosion mechanism is of great significance to guide the design and synthesis of new corrosion inhibitors.The effect and mechanism of the primary arguments on the process of CMP of SUS304 are firstly researched by mono-factorial method,and a new environment-friendly corrosion inhibitor chitosan oligosaccharide is proposed in this paper,which is analyzed from different angles such as experiments and theoretical calculations.The effect of chitosan oligosaccharide on the CMP process of SUS304 and its corrosion inhibition mechanism were studied.First of all,based on the previous orthogonal test parameters,the influence and mechanism of different pH,different oxidant concentrations,different particle sizes and concentrations of abrasive on CMP of SUS304 were researched by mono-factorial method.The result was indicative that a higher material removal rate can be obtained in acidic environment,but the strong corrosion of acidic environment is easy to form corrosion pits on the metal surface.The addition of oxidant promotes the anodic reaction on the metal surface and forms a loose and porous oxide film on the surface,hence improving the MRR and reducing surface quality better after polishing of SUS304 during CMP,but too high a concentration of oxidant can easily lead to the surface oxide film becomes dense,which inhibits the chemical reaction on the metal surface,resulting in a decrease MRR and debase surface roughness after CMP.The effect of abrasive concentration on the MMR during the CMP of SUS304 can be divided into three stages,namely the rapid increase stage,the linear correlation stage and the saturation stage.A new environment-friendly corrosion inhibitor chitosan oligosaccharide was proposed,and its corrosion inhibition performance and mechanism on SUS304 during the polishing process were studied by electrochemical,SEM,XPS,infrared spectroscopy and other tests.It was found that the concentration of chitosan oligosaccharides had a great influence on its corrosion inhibition efficiency,and the interfacial capacitance,polarization resistance and the inhibition rate showed a"concentration extreme"behavior with the change of concentration,and the highest inhibition rate was 68%when the concentration was 400 mg·L^-1.Corrosion inhibition rate,which can inhibit corrosion on the surface of 304 stainless steel by bonding active atoms such as N and O to surface Fe atoms,improve the smoothing rate of the SUS304surface during the CMP and the surface quality after polishing,and chitosan oligosaccharide molecules The amino and hydroxyl polar groups on the solution can complex with Fe²⁺or Fe³⁺in the solution to form a water-insoluble complex.This"bridge"complexation feature can further improve the compactness of the adsorption film and improve the resistance to steel.Based on the density functional theory（DFT）,calculate the molecular chemistry of chitosan oligosaccharides with different degrees of polymerization using the B3LYP method.The results show that the O atom on the hydroxyl group,the N atom on the amino group and the O atom on the ring are the main active adsorption sites.Electrons form coordination bonds with Fe atoms,and form a corrosion inhibitor film through chemical adsorption,thereby inhibiting the corrosion on the 304 stainless steel surfaces.Hydroxy groups,amino groups and other groups with strong electronegativity can specifically adsorb on the surface of stainless steel,further improving the interaction between corrosion inhibitor molecules and metal surfaces,and it is found that the degree of polymerization has no significant impact on the adsorption mechanism of corrosion inhibitor molecules.The dynamic simulation of the interaction between organic chitosan molecules with different degrees of polymerization and the Fe（110）surface and the film-forming mechanism was carried out by MD method.Compared with the vacuum environment,the type of corrosion inhibitor changes significantly,the main adsorption site changes from hydroxyl to amino,and the degree of polymerization has a more obvious effect on the adsorption form.Parallel adsorption on the SUS304 surface,increase the bonding strength with the Fe（110）and improve the surface coverage.In the process of polymolecular adsorption,organic molecules of chitosan oligosaccharides mainly have three stable configurations,namely,parallel adsorption,warping adsorption,and partial adsorption.Among them,the locally adsorbed molecules are prone to desorption under the action of water molecules to form localized corrosion.The corrosion inhibitor films formed by chitosan oligosaccharide organic molecules with different degrees of polymerization can effectively prevent the diffusion of 5kinds of corrosive ions（NO₃^-,H₂O,OH^-,O₂,H₃O⁺）to the metal surface,so as to achieve the effect of corrosion inhibition.The ability of the corrosion inhibitor film to inhibit the diffusion of charged ions is obviously stronger than that of neutral ions,and the inhibitory effect is more obvious with the increase of the degree of polymerization,and the corrosion inhibitor film formed by the increase of cohesive energy is more stable.