Preparation And Inhibition Behavior Of Znalce Layered Double Hydroxide Intercalated With HEDP

In the marine environment,high concentration of aggressive ions can cause serious corrosion,causing immeasurable economic and security losses.The most common pipeline material is carbon steel in seawater circulation cooling system,followed by corrosion problems can not be ignored.At present,the main anticorrosive methods for metal materials include selecting appropriate metal materials,coating protection,electrochemical protection and adding corrosion inhibitors.Among them,the green environment-friendly corrosion inhibitor technology with low cost,good corrosion inhibition effect and high utilization rate,has become a new research hotspot and very important practical value.In this paper,nanocomposite corrosion inhibitor of HEDP-LDHs was prepared by coprecipitation method and characterized by XRD,FT-IR,SEM,TEM and TG-DTG.The inhibition process and mechanism of three LDHs on carbon steel were analyzed,which provided theoretical basis for corrosion and protection in seawater circulation cooling system.The three hydrotalcites of ZnAl-NO₃,ZnAl-HEDP and ZnAlCe-HEDP all have the typical layered structure and high crystallinity.The size of LDHs is 0.1-1μm,the thickness is about 10nm,and the interlayer spacing is significantly increased.This shows that the interlayer spacing of LDHs is regulable,and the different anions make a big difference in interlayer spacing.At the same time,the addition of Ce has less effect on the interlayer spacing.The corrosion process and inhibition mechanisms of Q235 carbon steel in 3.5%NaCl solution were analyzed by electrochemical tests and immersion corrosion weightlessness experiments.The results showed that corrosive ions are Zn²⁺and Al³⁺from ZnAl-NO₃,Zn²⁺,Al³⁺and HEDP^3-from ZnAl-HEDP LDHs,and Zn²⁺,Al³⁺,Ce³⁺and HEDP^3-from ZnAlCe-HEDP LDHs.ZnAlCe-HEDP LDHs has the best corrosion inhibition and the corrosion inhibition mechanism was as follows:on the one hand,the corrosion anion of Cl^-in solution was captured by ion exchange,which can reduce the corrosion current density,increase the resistance value and effectively inhibit the occurrence of corrosion.On the other hand,the release of Zn²⁺,Al³⁺,Ce³⁺from the hydrotalcite laminate are capable of reacting with OH^-in solution,and the ion-exchanged HEDP^3-can chelate the iron ions from corrosion products.And there would be a protective film on the surface of Q235 steel composed of Zn（OH）₂,Al（OH）₃,Ce（OH）₃ and Fe-HEDP chelates to prevent further corrosion.Orthogonal experiment was used to optimize the synthesis process of ZnAl-HEDP LDHs and ZnAlCe-HEDP LDHs.The results showed that the optimum synthesis processes of ZnAl-HEDP LDHs were determined as Zn²⁺:Al³⁺=2:1 or 3:1,reaction temperature 40℃,crystallization temperature 100℃,and the optimum synthesisconditionsofZnAlCe-HEDPLDHsweren(M²⁺)n(M³⁺):=2:1,n(Al³⁺)n(Ce³⁺):=6:1,reaction temperature 35℃,crystallization temperature 105℃.