Acid solution is widely used in petrochemical, chemical cleaning, pickling and scaling and other industrial processes, resulting in serious metal corrosion problems. In order to improve the service life of industrial equipment and reduce industrial costs, it is necessary to carry out metal corrosion protection. As a simple and effective corrosion inhibitor, the design and development of a new type of efficient corrosion inhibitor is currently a research focus. As nitrogen-rich compounds, triazine derivatives not only contain unpaired N heteroatoms, but also have abundant π electrons.
As a double-asymmetric hydrophobic chain surfactant, the surface activity of T_4 is superior to that of symmetric surfactants (T_1, T_2 and T_3, T_5). (3) The corrosion inhibition performance of corrosion inhibitor on carbon steel in 1 M HCl medium was studied by static weight loss method and electrochemical method, and the influence of corrosion inhibition concentration and application temperature of corrosion inhibitor on corrosion inhibition performance was investigated. The corrosion inhibition effect of T_4 and T_5 at 0.01 mM and 0.05 mM, respectively, is more than 90%, indicating that the corrosion inhibitor has good corrosion inhibition performance at low concentration, and the optimal corrosion inhibition rate of T_4 at 20℃ is 95.28%. The corrosion inhibition performance of corrosion inhibitors increased with increasing concentration and decreased with increasing temperature. Under the same conditions, the inhibition effect of T_4 is slightly better, which proves that the inhibition effect of asymmetric surfactants is better than that of symmetric surfactants. The electrochemical impedance results showed that the corrosion inhibition mechanism was not changed by the addition of inhibitor. The potentiodynamic polarization corrosion current density decreases significantly with the addition of corrosion inhibitors, which proves that corrosion inhibitors can play a role in corrosion inhibition. All the five target corrosion inhibitors belong to the mixed type of anode and cathode corrosion inhibitors. (4) The surface analysis method proved that the corrosion inhibitor was adsorbed on the surface of carbon steel to form a film, and the corrosion of carbon steel was greatly inhibited. The surface morphology of carbon steel before and after the addition of corrosion inhibitor was analyzed by scanning electron microscopy.
The surface of carbon steel samples was flat after the addition of corrosion inhibitor. EDS analysis of the changes of O, N and Fe elements on the surface of carbon steel samples after adding corrosion inhibitor showed that the decrease of Fe element and the appearance of N element proved that corrosion inhibitor adsorbed on the surface of carbon steel. The contact Angle of water on the surface of carbon steel samples before and after corrosion proves that the surface roughness of carbon steel samples decreases after adding corrosion inhibitor, and the water contact Angle is larger than that of original carbon steel samples, which proves that corrosion inhibitor adsorbs on the surface of carbon steel and the hydrophobic chain is exposed to the surface of carbon steel. The surface analysis of carbon steel by XPS shows that the C=N, c-n ~+, n-h, -N= bonds in the corrosion inhibitor molecules appear on the surface of carbon steel samples, which further proves that the corrosion inhibitor molecules are adsorbed on the surface of carbon steel samples. (5) Corrosion kinetics and adsorption thermodynamics were used to investigate the corrosion inhibition mechanism of corrosion inhibitor molecules. The corrosion kinetics results show that the corrosion activation energy E_a and pre-exponential factor Ar increase with the increase of corrosion inhibitor concentration, and the corrosion reaction energy barrier of carbon steel increases, that is, the addition of corrosion inhibitor in the corrosion system increases the corrosion energy barrier and improves the corrosion inhibition performance. The adsorption thermodynamic results show that the corrosion inhibitor is in line with Freundluich isotherm adsorption on the surface of carbon steel. The adsorption of surface active triazine derivatives on the surface of carbon steel presents three stages at different concentrations. At low concentrations, the surface active triazine derivatives are adsorbed on the surface of carbon steel in a single molecular layer. As the concentration increases, the corrosion inhibitor molecules are adsorbed in multiple layers at medium concentration. At high concentration, saturated 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. The adsorption capacity of T_4 on carbon steel surface is the strongest, followed by T_5, T_3, T_2 and T_1. The five surface-active triazine derivatives have good corrosion inhibition properties on carbon steel in 1 M HCl. The surface activity is enhanced, the corrosion inhibition properties of corrosion inhibitor molecules are enhanced, and the surfactant molecules are adsorbed on the surface of carbon steel in multimolecular layers.
Post time: Mar-21-2023