Formulation Design And Performance Research Of Volatile Inhibitor For Carbon Steel

Compounding is the most commonly used and cost-effective method to obtain high-efficiency volatile corrosion inhibitors(VCI).The purpose of this article is to develop a compound VCI to deal with the atmospheric corrosion problem of carbon steel.At present,orthogonal experimental design is mostly used for the compounding of VCI.This article creatively introduces the mixture design into the development of VCI.Firstly,urea,urotropine,benzotriazole and sodium benzoate were compounded by orthogonal experimental design.It was concluded that the best formula of VCI containing the above four components was urea:urotropine:benzotriazole:sodium benzoate=1:6.67:10:1,the dosage was0.56 kg/m~3,and the inhibition efficiency was 89.23%.Then the mixture design of these four components was carried out based on Minitab.The optimal formula was calculated as urea:Urotropine:benzotriazole:sodium benzoate=0.0722:0.4642:0.4136:0.0500(i.e.1.44:9.28:8.27:1).When the dosage was 0.56 kg/m~3,the inhibition efficiency was 92.90%.The advantages and disadvantages of the two experimental design methods and the inhibition efficiency of the two formulations at the same dosage was compared,which proves the feasibility and superiority of mixture design in the development of VCI field.Through density functional theory(DFT),XPS,SEM,and contact angle measurement,the corrosion inhibition mechanism and performance on the carbon steel were studied.The results showed that the components of the VCI can chemically adsorb and vaporize on the surface of carbon steel.The VCI film formed on the surface of carbon steel had a fast speed;the coverage was comprehensive;the film of the inhibitor was hydrophobic and the state of the film was constantly adjusted.The electrochemical test was used to study the electrochemical behavior of VCI in simulated atmospheric corrosion water.From the open circuit potential,it could be seen that the addition of the VCI made the electrode rebehavior reached equilibrium faster than without VCI.From the polarization curve,it could be seen that the VCI was a mixed-type inhibitor with predominant anodic effectiveness.Its addition significantly reduced the corrosion rate of carbon steel.From the electrochemical impedance spectroscopies,it could be seen that the higher the concentration of the VCI,the greater the charge transfer resistance,the more complete and dense the film,but the fluctuation of adsorption film resistance(R_a)value also proved that the state of inhibitor film was constantly adjusted.From constant potential polarization curve,it could be seen that the VCI film had strong adsorption.The VCI film was not easy to be destroyed and even could exist at high potential.The VCI was made into volatile corrosion inhibitor paper(VCIP),and the best coating amount of the VCIP was determined to be 15 g/m~2through the vapor phase anti-corrosion screening test.The contact corrosion test verified that the VCIP would not cause corrosion of carbon steel when they close contacted in a humid environment.