Corrosion inhibitor used for protecting ancient cast iron antiques

[0013] According to the particularity of iron cultural relics, the present invention screens several industrial corrosion inhibitors that have been quite mature in industrial research and application. Z30 cast iron is used to simulate ancient cast iron samples and perform performance with the corrosion inhibitor of the present invention. Comparison and detailed description of the mechanism of action of the corrosion inhibitor of the present invention.

[0014] In the corrosion of ancient ironware, Cl - Will greatly promote the electrochemical reaction of ironware, and Cl - It can also accelerate the progress of local corrosion such as pitting, stress corrosion, intergranular corrosion and crevice corrosion, which is the biggest factor affecting the corrosion rate of ironware. Therefore, the present invention selects 3.5% NaCl solution as the corrosion environment to compare and analyze the corrosion inhibition performance of different corrosion inhibitors (the different corrosion inhibitors mentioned here include well-known corrosion inhibitors and the corrosion inhibitors provided by the present invention).

[0015] 1. Experimental part

[0016] 1. Sample: Since most of the outdoor ironware in ancient my country is cast iron (iron anchors are wrought iron), the present invention uses Z30 cast iron to simulate ancient ironware. Z30 cast iron is 50×25×2mm specification, in which C content is 3.3%, Si content is 2.8-3.2%.

[0017] 1) Using the weight loss method, the cast iron samples were suspended and soaked in 3.5% NaCl solution and 3.5% NaCl solution added with corrosion inhibitor for 168 hours and then taken out. The experimental results of the weight loss method are shown in Table 1 and Table 2.

[0018] Table 1: Weight loss results of blank sample (in 3.5% NaCl solution)

[0019]

[0020] Table 2: Weight loss results of adding corrosion inhibitor to 3.5% NaCl solution

[0021]

[0022] Note: In Table 2, serial numbers 1-1 to 1-3 are ethanolamine with a concentration of 1.5 mol/L, 2-1 to 2-3 are benzotriazole with a concentration of 8.5 mmol/L, and 3-1 to 3-3 It is sodium gluconate with a concentration of 2.3mmol/L, and 4-1~4-3 are 1.5mol/L ethanolamine+8.5mmol/L benzotriazole+2.3mmol/L sodium gluconate mixed corrosion inhibitor.

[0023] According to the experimental data in Table 1 and Table 2, in 3.5% NaCl solution, ethanolamine, benzotriazole, and sodium gluconate all have different degrees of corrosion inhibition to cast iron. Ethanolamine has the best corrosion inhibition effect. After mixing these kinds of corrosion inhibitors, the corrosion inhibition rate reaches more than 90%, indicating that there is a synergistic corrosion inhibition effect among the corrosion inhibitors, which enhances the corrosion inhibition.

[0024] 2) Polarization curve method

[0025] The Z30 cast iron was used as the working electrode to carry out the potentiodynamic scanning, and the potentiodynamic polarization curve was obtained. Use the potential V as the y-axis and the current density logarithm lg I as the x-axis. Compare the corrosion inhibition effects of various corrosion inhibitors through the graph curves of different corrosion inhibitors.

[0026] With 3.5% NaCl solution as the medium, different types of corrosion inhibitors are added (different types of corrosion inhibitors used in the polarization curve method are the same as those used in the weight loss method), and the total volume of the mixed solution is 250 mL. The Z30 cast iron is made into a working electrode with a 1cm×1cm square surface. After sanding the electrode surface smooth with 600#, 1000# sandpaper, use acetone to remove the oil on the surface and rinse with deionized water. The reference electrode is a saturated calomel electrode, and the auxiliary electrode is a platinum wire electrode. The scanning speed is 2mV/s, and the scanning range is -0.6~0.6V.

[0027] The polarization curve of Z30 cast iron in 3.5% NaCl solution with different corrosion inhibitors is shown figure 1. The self-corrosion potential of Z30 cast iron in blank solution is -0.72753V, the self-corrosion potential of BTA is -0.63080V, the self-corrosion potential of PMP is -0.65205V, the self-corrosion potential of ethanolamine is -0.51939V, BTA+ethanolamine+sodium gluconate The self-corrosion potential of -0.47267V. The cathodic polarization curve of the corrosion inhibitor is similar to that of the blank solution. The anodic polarization curve changes greatly, and the current decreases to different degrees at the same potential. It can be seen that these several corrosion inhibitors can inhibit the anodic dissolution process of metals and belong to the anode type corrosion inhibitor. Among them, the polarization curve in ethanolamine solution begins to show a passivation peak at about -0.70000V. As the potential increases, the corrosion current basically remains unchanged. At about -0.20000V, the film is broken down and passivation occurs. . And the polarization curve in the BTA+ethanolamine+sodium gluconate mixed corrosion inhibitor also showed a passivation peak around -0.70000V, and the passivation current was significantly reduced, which shows that the addition of BTA and sodium gluconate of the present invention can improve the ethanolamine The film-forming effect of the cast iron sample has a corrosion inhibition synergistic effect among the three, which improves the corrosion inhibition rate.

[0028] 3) Scanning electron microscope test

[0029] Grind, rinse, de-oil, dehydrate and dry the Z30 cast iron sheet. The specific operation steps are the same as the weightlessness method. The treated iron pieces were suspended and soaked in 3.5% NaCl solution of different corrosion inhibitors for 96 hours (different types of corrosion inhibitors used in the scanning electron microscope test method are the same as those used in the weight loss method). After taking out the iron piece, rinse it with deionized water, dehydrate it, blow it dry with a hair dryer, and put it into a drying dish. The surface morphology of the iron sheet before and after corrosion inhibition was analyzed by scanning electron microscope.

[0030] Figure 2A , Figure 2B The secondary electron image and backscattered electron image of the Z30 cast iron without corrosion inhibitor after corrosion in 3.5% NaCl solution for 168 hours. Figure 2C , Figure 2D The secondary electron image and backscattered electron image of Z30 cast iron added with BTA+ethanolamine+sodium gluconate mixed corrosion inhibitor after corrosion in 3.5% NaCl solution for 168 hours. It can be seen from the comparison between the corrosion inhibitor and the blank sample picture that the corrosion degree of the Z30 cast iron in the NaCl solution after the corrosion inhibitor of the invention is added is significantly lower than that without the corrosion inhibitor.

[0031] It can be seen from the results of the above three test methods that benzotriazole, ethanolamine and sodium gluconate have different degrees of corrosion inhibition effects on Z30 cast iron. Among them, ethanolamine has the best corrosion inhibition effect. When ethanolamine is mixed with benzotriazole and sodium gluconate, the corrosion inhibition coordination effect occurs, the corrosion inhibition effect is significantly improved, and it has good corrosion inhibition for Z30 cast iron.