The Preparation And Research Of Mannich Base Inhibitor

Metal corrosion has become a serious social problem,not only caused a lot of economic losses,but also brought a huge security risk.Corrosion inhibitors are an effective means of mitigating metal corrosion.Mannich base corrosion inhibitor due to its good stability and dispersion,low toxicity and other advantages,and is widely used.Mannich base contains nitrogen,oxygen and other heteroatoms,in there heteroatoms have unidentified lone pairs electrons,they could enter the empty orbit of metal atoms,then corrosion inhibitor molecules can adsoped on the metal surface.In order to prepare corrosion inhibitor with good efficiency,various aldehyde,ketone and amine,in mannich reaction were selected to obtain excellent performances of inhibitors.The results indicated that the corrosion efficiency of obtained products from formaldehyde,o-toluidine,benzylideneacetone(denoted as MNX-A)and formaldehyde,o-toluidine,p-methoxyacetophenone(denoted as MNX-B)are much better than others.The effects of reaction temperature,reaction time,reaction pH and molar ratio(aldehydes:ketones:amines)on the efficiency of corrosion inhibitor were investigated by single factor and orthogonal experiments.The preparation conditions of MNX-A and MNX-B were optimized.The optimized conditions for preparation of MNX-A addressed as follows: 2h,70℃,the pH was 3,the molar ratio(aldehydes:ketones:amines)was 1:1:1.Under there conditions the corrosion inhibition efficiency of steel was 93.95% and the isolated yield was 83.14%.The optimized conditions for preparation of MNX-B addressed as follows:3h,60℃,the p H was 2,the molar ratio(aldehydes:ketones:amines)was 1:1:1.Under there conditions the corrosion inhibition efficiency of steel was 92.45% and the isolatede yield was 86.34%.Besides the structure of MNX-A and MNX-B were determined by 1H NMR.The efficiency of the corrosion inhibitor was measured with the change of corrosion temperature,corrosion time,hydrochloric acid concentration and corrosion inhibitor concentration by weight loss method.The corrosion inhibition efficiency of MNX-A and MNX-B were increased initially and then decreased with the increasing of temperature and hydrochloric acid concentration,With the increase of the concentration of corrosion inhibitor and the prolonging of corrosion time,the efficiency of the corrosion inhibitor were increased initially and then constant.The adsorption of MNX-A and MNX-B on the surface of N80 steel were conform to the Langmuir isothermal adsorption model,ΔG0 were 33.49kJ/mol and-32.64kJ/mol respectively,all located between-20kJ/mol ~-40kJ/mol,so the adsorption of corrosion inhibitors on metal surface were the mix of chemical adsorption and physical adsorption.Dissolution experiments show that when the concentration of corrosion inhibitor less than 1500mg/L,the dispersion is good.It was found that the corrosion potentials of MNX-A and MNX-B are both less than 85 mV by polarization curve analysis,demonstrating that they are kinds of mixed type corrosion inhibitor,the corrosion inhibition efficiency calculated by the corrosion current density is basically consistent with the corrosion inhibition efficiency obtained by the weight loss method.By analyzing the AC impedance diagram and simulating the circuit diagram HCl solution,the distribution of corrosion inhibitor in the solution was studied,and the corrosion inhibition mechanism was deduced.The corrosion surface of N80 steel was effectively controlled by scanning electron microscopy(SEM).The results showed that the corrosion inhibitors of MNX-A and MNX-B have a good inhibitory effect on the N80 steel surface.In order to study the adsorption of the corrosion inhibitor in the metal surface within 30 min,measure the impedance every 5min,the result indicate that the adsorption on the metal surface reaches equilibrium at about 20 min.The corrosion inhibition efficiency were not ideal when the temperature and acidity of the single corrosion inhibitor became higher.In order to improve the corrosion resistance of higher temperature and acidity,add other compounds into single corrosion inhibitor.Select a variety of substances then mix them with the corrosion inhibitors MNX-A and MNX-B,the effect of there compound concentration on efficiency was studied,the result showed that KI,sodium molybdate,hexamethylenetetramine and thiourea have good synergistic effect on MNX-A and MNX-B.