| Acid solutions are widely used in a series of industrial processes such as petrochemicals,chemical cleaning,as well as,pickling and descaling,which causes serious metal corrosion problems.In order to expand the service life of industrial equipment and reduce industrial costs,it is necessary to protect the metal against corrosion.To date,adding corrosion inhibitor is regarded as a simple and effective corrosion inhibition method,and designing and developing a new type of high-efficiency corrosion inhibitor becomes a hot spot of the current research.As nitrogen-riched compounds,triazine derivatives,the potential corrosion inhibitors with high efficiency,contain not only unpaired N heteroatoms,but also have rich?electrons,which can be adsorbed on the surface of carbon steel via an intereaction with metals.Triazine derivatives with surface activities were synthesized by using cyanuric chloride as the matrix,and introducing hydrophilic and hydrophobic groups to make its surface active,by which,the solubility and directional adsorption capacity of triazine derivatives were improved.The synthesized triazine derivatives with surface activity can be used as metal corrosion inhibitors with high efficiency and low dosage.The main research contents are as follows:?1?Triazine derivatives with surface activities?T1,T2,T3,T4,T5?were synthesized by using cyanuric chloride,fatty amines?n-hexylamine,n-octylamine?and N,N-dimethyl-1,3-propanediamine as raw materials.High resolution mass spectrometry?ESI-MS?,Fourier infrared?FT-IR?and nuclear magnetic resonance?1H NMR?were used to characterize the structure of the target corrosion inhibitor.?2?The surface activity of the corrosion inhibitor in 1 M HCl solution was measured by hanging tablet method.The results illustrated that the triazine derivatives showed good surface activity in 1 M HCl and reduced the surface tension of the system significantly.The surface activity of T4 is the best,with cmc of 0.21 mM and?cmcmc of 22.87mN m-1,followed by T5,T3,T2 and T1.As a surfactant with double asymmetric hydrophobic chains,T4 has better surface activity than symmetric surfactants?T1,T2,T3 and T5?.?3?The static weight loss method and the electrochemical method were used to study the corrosion inhibition performance of the corrosion inhibitor on carbon steel in 1 M HCl medium,and the effects of the concentration of the corrosion inhibitor,the application temperature as well as several factors on the corrosion inhibition performance were investigated.The corrosion inhibition effect of T4 and T5 at 0.01 mM and 0.05 mM can reach more than 90%,indicating that the corrosion inhibitor has a good anti-corrosion effect at a low concentration,and the optimal corrosion inhibition rate of T4 reaches 95.28%at 20?.The corrosion inhibition performance of corrosion inhibitors increases with the increase of concentration and decreases with the increase of temperature.Under the same conditions,the corrosion inhibition effect of T4 is slightly better,which proves that the asymmetric surfactant has better corrosion inhibition effect than the symmetric surfactant.The electrochemical impedance results show that the addition of the corrosion inhibitor does not change the corrosion inhibition mechanism,and the dynamic potential polarization corrosion current density decreases significantly with the addition of the corrosion inhibitor,illustrating that the corrosion inhibitor can play the role of corrosion inhibition,and all five target corrosion inhibitors belong to mixed anode and cathode corrosion inhibitors.?4?The surface analysis method proves that the corrosion inhibitor is adsorbed on the surface of the carbon steel and forms a film,and the corrosion of the carbon steel is suppressed seriously.he surface morphology of the carbon steel before and after adding the corrosion inhibitor.The surface morphology of the carbon steel before and after adding the corrosion inhibitor.The surface of the carbon steel sample was smooth after the addition of corrosion inhibitor,proving that the corrosion inhibitor played a corrosion inhibitory effect;In EDS analyses,the decrease of Fe element and the appearance of N element prove that the corrosion inhibitor is adsorbed on the surface of carbon steel.The contact angle of water on the surface of the carbon steel sample before and after corrosion proves that the surface roughness of the carbon steel sample decreases after the addition of the corrosion inhibitor,and the water contact angle is greater than the water contact angle of the original carbon steel sample,illustrating that the corrosion inhibitor is adsorbed on the surface of the carbon steel,and the hydrophobic chain is exposed on the surface of the carbon steel.XPS analysis of the surface of carbon steel showed that the C=N,C-N+,N-H,and-N=bonds in the inhibitor molecules appeared on the surface of the carbon steel sample,which further proved that the inhibitor molecules were adsorbed on the surface of the carbon steel sample.?5?Corrosion kinetics and adsorption thermodynamics were used to explore the corrosion inhibition mechanism of corrosion inhibitor molecules.Corrosion kinetics results showed that both the corrosion activation energy Ea and pre-finger factor Ar increased with the concentration after adding the corrosion inhibitor,indicating that the carbon steel corrosion reaction energy barrier was increased,and the reaction became more difficult.The addition of corrosion inhibitor increased the corrosion energy barrier and improved the corrosion inhibition performance.Adsorption thermodynamic results showed that the corrosion inhibitor adsorbed on the surface of the carbon steel fitted well with Freundluich isotherm,and the surface-active triazine derivatives adsorbed on the surface of the carbon steel at different temperatures can be divided into three stages:at low concentrations,the surface-active triazine derivatives molecules are adsorbed on the surface of carbon steel by monolayer adsorption;as the concentration increases,the inhibitor molecules undergo multilayer adsorption at medium concentration;at high concentrations,saturation adsorption is basically achieved.?6?Material Studio 5.5 was used for molecular dynamics simulation to analyze the adsorption process of triazine derivative molecules in 1 M HCl medium.T4 has the strongest adsorption capacity on the surface of carbon steel,followed by T5,T3,T2 and T1.The synthesized five surface-active triazine derivatives have good corrosion inhibition performance for carbon steel in 1 M HCl.The surface activity and corrosion inhibition performance of the corrosion inhibitor molecules are enhanced,and the surfactant molecules can be adsorbed on the surface of carbon steel by multi-molecular layer adsorption. |
PDF Full Text Request