Theoretical Research On Corrosion Resistance Of Fe-Cr/Ni Alloy

Fe-Cr/Ni alloys are widely used because of their good corrosion resistance.Although the corrosion resistance of the alloy is better than the single metal,corrosion is still an important factor affecting the service life of the material.Improve the corrosion resistance of metal materials is an important anti-corrosion means.Corrosion experimental methods can determine the type and rate of corrosion and the composition and properties of the corrosion product film,but it cannot directly observe the microscopic process of corrosion.Molecular simulation technology can compensate for the lack of experimentation and provide a clear microscopic corrosion process,reveal the corrosion mechanism.In this paper,density functional theory method was used to study the optimal adsorption sites of water and its dissociation products on Fe?110?,and the dissociation process of water was analyzed.Then,the adsorption of water and its dissociation products on FeCr?110?and FeNi?110?surfaces was studied,and the dissociation process of water was analyzed.Finally,the interaction between Cl and hydroxylated Cr₂O₃?001?and Fe₂O₃?001?was studied.The main conclusions were presented as following:1.Obtained the optimal adsorption site of various adsorbates on the surface of metal and alloy.The results showed that the optimal adsorption site does not change significantly after addition of Cr and Ni.The optimal adsorption site for H₂O was the top site and OH/O/H was hollow site.However,their adsorption energy increased,the addition of Cr led to the adsorption energy of H₂O/OH/O/H at the optimum adsorption site increased by 0.055 eV,0.272 eV,0.317 eV,and 0.030 eV,respectively.After adding Ni,the adsorption energy of H₂O/OH/O/H at the optimum adsorption site increased by 0.025 eV,0.045 eV,0.091 eV,and 0.025 eV,respectively.when the Cr and Ni add to Fe crystal it can improve the adsorption energy of water dissociation products on the surface which led to form a more compact passivation film on the surface.2.The dissociation of H₂O in Fe?110?,FeCr?110?and FeNi?110?was studied by the transition state theory.When the Cr atoms were added to Fe?110?,the energy barriers of the two-step elementary reactions for H₂O dissociation on its surface changes little.However,When the Ni atoms were added to Fe?110?,the energy barriers of the two-step elementary reactions for H₂O dissociating increased 8.23 kJ·mol-1 and 22.84kJ·mol-1,respectively.The addition of Ni can improve the corrosion resistance.3.The interaction between Cl and hydroxylated Cr₂O₃?001?and Fe₂O₃?001?was studied by density functional theory method.The results show that When the OH and Cl coexists on the surface of Cr₂O₃?001?and Fe₂O₃?001?,the surface of their configuration would deform with the substitution of Cl atoms increase on the surface.When a Cl atom of the surface layer was inserted into the inner layer,as the coverage of the surface layer Cl atoms increases,both the Fe₂O₃?001?configuration and the Cr₂O₃?001?configuration became relaxed,however,the deformation of Fe₂O₃?001?configuration is more severe than Cr₂O₃?001?at the same Cl coverage of surface,the insertion a Cl atom into the inner layer had a greater effect on the Fe₂O₃?001?configuration.Therefore,the addition of Cr can improve its corrosion resistance by forming a more protective passivation film on its surface.The above conclusions indicate that the addition of Ni to Fe crystal can improve the corrosion resistance of the matrix and the addition of Cr can improve the corrosion resistance of the matrix by forming a more protective passivation film on the surface.