Study On The Corrosion Inhibition Performance And Mechanism Of Compound Vapor Phase Inhibitor For Carbon Steel

Vapor phase inhibitor can effectively reduce the corrosion rate of carbon steel,and can block or completely terminate the atmospheric corrosion process of metals.Gas phase corrosion inhibitor has been widely used because of its advantages of low cost,simple process,convenient operation,long storage time,good effect and meeting the requirements of combat readiness.The industry has begun to restrict the use of nitrous acid and its derivatives and other efficient traditional corrosion inhibitors.Based on this,this paper will develop a kind of environmentally friendly vapor phase corrosion inhibitor formula.At the same time,weight loss method,Tafel polarization curve test and impedance spectrum test were used to study its corrosion inhibition performance and mechanism for carbon steel.Firstly,the inhibition performance of 15 kinds of gas phase corrosion inhibitors was investigated by volatility test and gas phase corrosion inhibition ability.Considering environmental protection,price and other factors,polyaspartic acid(PASP),sodium benzoate,urea and Urotropine were selected as the components of the gas phase corrosion inhibitor formula.Based on the study of inhibition efficiency and inhibition mechanism of single component inhibitor,the orthogonal experiment of weight loss inhibition efficiency was carried out,and the optimum formula was obtained as follows: polyaspartic acid 15 g/L,urotropine 6 g/L,sodium benzoate 4 g/L,urea 2 g/L.The corrosion inhibition performance of the compound inhibitor showed that the inhibition efficiency of the compound inhibitor for carbon steel could reach 92.6%.The composite system belongs to anodic inhibition type.Weight loss method,Tafel polarization curve and electrochemical impedance spectroscopy were used to study the effects of p H value and temperature on the inhibition performance of the compound inhibitor.The results show that the inhibitor formula has higher inhibition efficiency under neutral and weak alkaline conditions,which can reach more than90%.The optimum temperature is 25 ℃,and the inhibition efficiency decreases with the increase of temperature.The long-term inhibition performance of the composite inhibitor shows that the first 10 days is the growth period of the adsorption film,and the inhibition efficiency can maintain more than 90% after that.According to the calculation of the activation energy of corrosion reaction and the analysis of the molecular adsorption behavior of corrosion inhibitor,the adsorption energy of composite corrosion inhibitor increases the corrosion reaction energy barrier and reduces the corrosion rate.Through organic synthesis experiments,amine,hydroxyl and aromatic groups were introduced into PASP.The elements and valence bond states of dopamine modified polyaspartic acid(PASP-Dop)were characterized by XPS.It was verified that PASP-Dop was successfully synthesized and showed good corrosion inhibition potential.The study on the inhibition performance of PASP-Dop showed that the dosage of PASP-Dop could be reduced and the inhibition efficiency could be improved.The effective adsorption of PASP and PASP-Dop molecules at the carbon steel/solution interface follows the Langmuir adsorption isotherm.The Gibbs free energy of PASP adsorption process is-28.738 k J/mol,and the Gibbs free energy of PASP-Dop adsorption process is-33.154 k J/mol.The study of corrosion inhibition mechanism shows that the donor acceptor interaction and aromatic ring of PASP-Dop between π electron and d orbital of iron vacancy can provide better protection for carbon steel.