Study On Corrosion Inhibition Performance Of Surfactant And Heterocyclic Ring Composite For Carbon Steel In Hydrochloric Acid Solution

Pickling is an effective means of metal rust removal in the industry,but there is a risk of excessive corrosion during pickling.The addition of pickling inhibitor to the pickling solution is an effective way to prevent excessive metal corrosion and improve pickling efficiency.Heterocyclic compounds have good chemical adsorption properties.Surfactants have good directional adsorption properties.Both of them are used as pickling inhibitors.In this dissertation,we use cyanuric chloride as the precursor to insert non-polar groups?n-hexylamine,n-octylamine?and polar groups?N,N-dimethyl-1,3-propanediamine?to synthesize two surfactants:2-n-hexylamino-4-?3-dimethylamino-propylamino?-6–hydroxy-1,3,5-s-triazine?C6?,2-n-octylamino-4-?3-Dimethylamino-propylamino?-6-hydroxy-1,3,5-s-triazine?C8?were characterized by IR,ESI-MS and ¹HNMR.And with 2-amino benzimidazole,2-mercaptobenzothiazole equimolar ratio compounded as a corrosion inhibitor.The corrosion of 45#carbon steel in a medium of 1mol/L hydrochloric acid for48 hours was studied by laboratory evaluation method?weight loss method,adsorption thermodynamics,electrochemical method,quantum chemical calculation and molecular dynamics simulation?.The impact of the situation is as follows:Surface activity of two surfactants and mixed inhibitor system were studied by surface tension test.The results show that the two surfactants can effectively reduce the surface tension of 1M HCl solution and decrease sharply with the increase of the concentration until the critical micelle concentration is reached.The surface tension of the system tends to be stable,and finally stays at 30 mN m^-1 or so.The critical micelle concentrations of C8 and C6 were?0.1 mM?and?0.5 mM?,respectively.This shows that both surfactants can form saturated adsorption at the interface at lower concentrations.The static weight loss test was conducted to investigate the influence of the concentration of the surfactant and the molar ratio of the surfactant and the heterocyclic small-molecule corrosion inhibitor after the compounding and the ambient temperature on the corrosion inhibitor.The results show that at 20°C,The corrosion inhibition efficiency of the surfactant alone was as high as 94%,and the corrosion inhibition efficiency was stable at over 97%,especially when the added amount exceeded the critical micelle concentration.After the compounding,the corrosion inhibition efficiency also improved slightly.However,with the increase of the corrosive environment temperature,the corrosion inhibition efficiency of the surfactant was continuously reduced,and the corrosion inhibition efficiency of the corrosion inhibition system after compounding was obviously suppressed.When the addition amount of the C8 mixed with 2-mercaptobenzothiazole compound was 5mM,the corrosion inhibition efficiency in the corrosive environment at 50°C could still be kept at 92%,indicating that the surfactant and heterocyclic small molecule corrosion inhibitor compounding can effectively reduce the corrosion time.The amount of the additive increases the stability of the corrosion inhibitor to the temperature.The experiments of electrochemical impedance spectroscopy and potentiodynamic polarization curves have studied the protective effect of corrosion inhibitors on metals during the electrochemical corrosion process and their action mechanism.The results show that the surfactants form a protective film on the surface of carbon steel electrodes.Effectively prevents material exchange between metals and corrosive media.Surfactants and surfactants with 2-aminobenzimidazole and 2-mercaptobenzothiazole mixed system on the metal surface film formation process is based on physical adsorption,the carbon steel electrode cathode and anode corrosion process have a good hindrance,belong to the mixed inhibition type corrosion inhibitor.Adsorption thermodynamic studies show that the adsorption of surfactants and surfactants with 2-aminobenzimidazole and 2-mercaptobenzimidazole on carbon steel surface is based on physical adsorption-based mixed adsorption,in line with Langmiur adsorption isotherm.Quantum chemical calculations and molecular dynamics simulation methods were used to study the adsorption capacity of inhibitor molecules and metals from a microscopic point of view.The simulation results show that either the single surfactant or the heterocyclic small molecule corrosion inhibitor has excellent corrosion inhibitor characteristics and can be effectively adsorbed on the metal surface.The adsorption energy of the system at the interface after compounding is significantly enhanced compared to the two types of individual corrosion inhibitors.