Fabrication Of Anti-corrosion Material Zn₃?PO₄?₂/Zn₂Fe?PO₄?₂ And Organic Corrosion Inhibitor On Q235 Carbon Steel And Their Application Research

With the continuous development of industrial technology,the utilization rate of metals in industry and daily life has obviously increased,especially Q235 carbon steel,because of its low cost,low strength,high plasticity and good welding performance,widely used in a variety of industries.However,the phenomenon of corrosion cannot be avoided in the process of use which has attracted wide attention of the whole society.The corrosion not only causes serious economic losses,environmental pollution,but also will cause casualties.Therefore,it is of great significance to take protective measures against metals to maximize their service life.At present,the protection is mainly considered from the following two aspects:?1?providing a physical barrier between the metal surface and the corrosive medium,?2?adding organic corrosion inhibitor to the acidic solution can solve the problem of"corrosion"caused by the treatment of iron metals.A uniform and dense composite coating were successfully developed on Q235carbon steel by a simple and environmentally friendly method.The surface morphology and chemical composition of the coatings were analyzed by scanning electron microscopy?SEM?,energy-dispersive X-ray spectroscopy?EDX?and X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?.The corrosion resistances of coatings were investigated by electrochemical impedance spectra?EIS?,potentiody-namic polarization and saline immersion experiments.The results showed that the optimum coating consists of homogeneous Zn₃?PO₄?₂·4H₂O/Zn₂Fe?PO₄?₂·4H₂O?rod-like?particles.The composite coating cm^-2),which was enhanced by 5 orders of magnitude compared with that of bare Q235 steel substrate.More importantly,the annual corrosion rate of the coating reached 0.001 mm/a after immersion in 3.5 wt%Na Cl solution for 5 days,indicating that the coating has excellent long-term corrosion protection stability.The optimum technological conditions of Zn₃?PO₄?₂/Zn₂Fe?PO₄?₂ composite coating were studied by single factor test.The influence of the reaction ratio,mass concentration,Fe SO₄ content,template agent,p H,reaction temperature and reaction time on the corrosion resistance of the film were investigated by using the polarization curve.The final conditions were determined as follows:m?KH₂PO₄?:m?Zn SO₄?=1:3,[KH₂PO₄]=5 g/l,[Zn SO₄]=15 g/l,[Fe SO₄]=2 g/l,the template agent was selected as OP-10,[OP-10]=1 g/l,p H=4.5,T=45°c,t=48 h.Finally,the film formation and corrosion process of the composite coating were further studied under the optimal conditions.Butyl imidazole bromide was prepared by two-step simple reaction.The inhibitory effect,adsorption behavior and thermodynamic parameters of different concentrations of inhibitors in 0.5M H₂SO₄ solution were studied.Electrochemical test and weight loss test show that the corrosion inhibition effect is best when the concentration is 80 ppm;adsorption thermodynamics shows that the adsorption of alkyl imidazole bromide salt on the surface of Q235 carbon steel conforms to the Langmuir adsorption isotherm,and belongs to the mixed type absorption inhibitor.The adsorption process is spontaneous,endothermic,and entropy-increasing reaction process.SEM results show that there is no obvious corrosion phenomenon on the surface at 80 ppm,and the surface is closer to the polished sample,which can be used as a good corrosion inhibitor.Finally,due to the composition of Q235 carbon steel is similar to that of iron,the alkyl imidazole corrosion inhibitor was applied to the iron rust removal and desalination process,and the Zn₃?PO₄?₂/Zn₂Fe?PO₄?₂ composite material was used to inhibit the iron.The results show that the imidazole corrosion inhibitors studied in this paper can effectively avoid re-corrosion caused by the process of rust removal and desalination.The corrosion resistance of the samples after corrosion inhibition is significantly improved,which has certain application value.