A pitting corrosion inhibitor for inhibiting pitting corrosion of stainless steel in cooling water containing manganese dioxide and a preparation method and application thereof

Abstract

The present application relates to a kind of for inhibiting the pitting corrosion inhibitor of stainless steel in containing manganese dioxide cooling water pitting corrosion and its preparation method and application, the pitting corrosion inhibitor contains sulfide and surfactant, preparation method is first added to water surfactant, then add sulfide, after stirring, dissolution obtains pitting corrosion inhibitor.Compared with prior art, the present application can better inhibit the pitting corrosion promoting effect of manganese dioxide to stainless steel.

Description

Technical Field

[0001] This invention relates to the field of corrosion inhibition technology, and in particular to a pitting inhibitor for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, its preparation method and application. Background Technology

[0002] Microorganisms are considered a significant factor in the corrosion of cooling pipes in circulating cooling water systems, particularly affecting common stainless steel cooling pipes. In recent years, there have been frequent cases of pitting corrosion in stainless steel cooling water systems caused by manganese microorganisms, drawing attention to corrosion problems caused by manganese dioxide deposition. Manganese dioxide-induced pitting corrosion in stainless steel is characterized by short failure time and severe pitting, potentially causing significant damage to condensers.

[0003] When manganese dioxide is present in cooling water, it can cause a positive shift in the open-circuit potential of stainless steel, making it higher than its pitting potential in the cooling water, leading to pitting corrosion. Commonly used passivating corrosion inhibitors are ineffective against this type of corrosion because they can further increase the open-circuit potential. Therefore, more effective pitting corrosion inhibitors are needed to control the corrosion of stainless steel. Summary of the Invention

[0004] The purpose of this invention is to provide a pitting inhibitor for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, its preparation method and application, which has a good pitting inhibition effect.

[0005] The objective of this invention can be achieved through the following technical solution: a pitting inhibitor for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, wherein the pitting inhibitor contains sulfides and surfactants.

[0006] Preferably, in the pitting corrosion inhibitor, the sulfide concentration (calculated as sulfide ions) ranges from 1 to 100 mg / L; and the surfactant concentration ranges from 0 to 200 mg / L.

[0007] More preferably, in the pitting corrosion inhibitor, the sulfide concentration (calculated as sulfide ions) ranges from 1 to 20 mg / L; and the surfactant concentration ranges from 40 to 60 mg / L.

[0008] Preferably, the sulfide is soluble in water and produces sulfur ions.

[0009] More preferably, the sulfide is Na2S·9H2O.

[0010] Preferably, the surfactant can form an adsorption film on the stainless steel surface.

[0011] More preferably, the surfactant is sodium dodecylbenzenesulfonate.

[0012] A method for preparing the above-mentioned pitting inhibitor for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water involves first adding a certain concentration of surfactant to water, then adding a certain concentration of sulfide (calculated as sulfide ions), stirring and dissolving to obtain the pitting inhibitor.

[0013] More preferably, the pitting inhibitor is prepared at room temperature.

[0014] More preferably, the stirring time is 1 to 20 minutes.

[0015] An application of the above-mentioned pitting inhibitor for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, wherein the pitting inhibitor is used in a neutral aqueous solution, such as industrial cooling water.

[0016] Preferably, the cooling water contains manganese dioxide or manganese microorganisms.

[0017] Preferably, the pitting corrosion is caused by the deposition of manganese dioxide in the cooling water on the stainless steel surface.

[0018] Preferably, the pitting inhibitor is used to inhibit pitting corrosion of stainless steel cooling pipes caused by manganese dioxide or manganese microorganisms in the cooling water.

[0019] The stainless steel pitting inhibitor of this invention is particularly suitable for controlling pitting corrosion of stainless steel in circulating cooling water systems containing manganese microorganisms. When circulating cooling water systems contain manganese microorganisms, manganese dioxide is produced and deposited on the surface of the cooling pipes. This manganese dioxide deposition causes the open-circuit potential of the stainless steel cooling pipes to shift positively above its pitting potential, leading to rapid pitting corrosion. When the pitting inhibitor is added, the reducing agent sulfide ions react with the strong oxidizing agent manganese dioxide, inhibiting the positive shift of the stainless steel's open-circuit potential. Simultaneously, the surfactant has a certain peeling and removal effect on the microbial film and manganese dioxide deposits on the stainless steel surface, and can form an adsorption film on the stainless steel surface, inhibiting the potential destructive effect of sulfide ions on the stainless steel passivation film. This pitting inhibitor can effectively reduce pitting corrosion of stainless steel in manganese dioxide-containing cooling water, significantly improving the corrosion resistance of stainless steel.

[0020] Conventional passivating corrosion inhibitors are not effective in inhibiting pitting corrosion of stainless steel in cooling water containing manganese dioxide or manganese microorganisms.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The pitting corrosion inhibitor of the present invention has a good inhibitory effect on the pitting corrosion of stainless steel in cooling water containing manganese dioxide or manganese microorganisms, and is low in cost and simple in process.

[0023] 2. When the stainless steel surface in the cooling water contains manganese dioxide deposits or manganese microorganisms, the stainless steel is prone to pitting corrosion. The pitting corrosion inhibitor of the present invention reduces the oxidizing power of oxides by sulfur ions and inhibits the positive shift of the open circuit potential of stainless steel. It removes the deposits of manganese dioxide or manganese microorganisms on the stainless steel surface by surfactants and forms an adsorption protective film on the stainless steel surface, thereby inhibiting the pitting corrosion of stainless steel.

[0024] 3. The pitting corrosion inhibitor of this invention uses few types of inexpensive raw materials, is simple to prepare, and has low cost.

[0025] 4. The pitting corrosion inhibitor prepared by this invention can perform impact treatment on cooling water containing manganese dioxide, effectively inhibiting the pitting corrosion promoting effect of manganese dioxide on stainless steel. Attached Figure Description

[0026] Figure 1 Open circuit potential diagram of stainless steel with pitting inhibitor added to simulated cooling water containing manganese dioxide;

[0027] Figure 2 Nyquist plot of stainless steel after adding pitting inhibitor to simulated cooling water containing manganese dioxide;

[0028] Figure 3 Bode plot of stainless steel after adding pitting inhibitor to simulated cooling water containing manganese dioxide;

[0029] Figure 4 This is a micrograph of the surface of stainless steel in simulated cooling water containing manganese dioxide. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0032] Example 1

[0033] A pitting inhibitor for stainless steel, the pitting inhibitor comprising a sulfide and a surfactant, wherein the concentration of the sulfide (calculated as sulfide ions) is 10 mg / L.

[0034] The preparation method of the above pitting inhibitor is as follows: 0.75 g of Na₂S·9H₂O is added to 100 mL of deionized water to obtain a 1 g / L sulfide ion solution. 25 mg of sodium dodecylbenzenesulfonate is added to 495 mL of deionized water and stirred until evenly distributed. Then, 5 mL of the above 1 g / L sulfide ion solution is added, and the mixture is stirred for 5 min to obtain the pitting inhibitor, which contains 10 mg / L sulfide ions and 50 mg / L sodium dodecylbenzenesulfonate.

[0035] Example 2

[0036] The pitting inhibitor prepared in Example 1 was added to cooling water containing manganese dioxide, and its effect on inhibiting pitting corrosion of stainless steel was tested. The specific experimental method is shown below.

[0037] (1) Experimental materials and experimental media

[0038] The basic composition of the simulated cooling water used in the experiment was: 20 mg / L Ca 2+ 6 mg / L Mg 2+ 360 mg / L SO4 2- 300mg / L Cl - 379 mg / L Na + 122 mg / L HCO3 - .

[0039] The experimental material was 304 stainless steel. The stainless steel was processed into test pieces with a working surface of 1cm × 1cm. Wires were soldered to the back of the working surface, and the non-working surface was sealed with epoxy resin. Before the experiment, the test pieces were polished with sandpaper ranging from 0# to 6#, cleaned with anhydrous ethanol, and dried at room temperature for later use.

[0040] (2) Test method

[0041] Electrochemical tests using the stainless steel electrode were performed on a CHI660E electrode using a three-electrode system: a saturated calomel electrode as the reference electrode, a platinum electrode as the auxiliary electrode, and a stainless steel electrode as the working electrode. The electrochemical impedance spectroscopy (EIS) was conducted in the frequency range of 10 mHz–100 kHz with an amplitude of 10 mV. The experimental temperature was 45 °C.

[0042] (3) Test Results

[0043] The pitting inhibitor from Example 1 was added to simulated cooling water containing manganese dioxide for open-circuit potential testing. The results are shown in [Figure 1]. Figure 1 .

[0044] As shown by curve 1 in the figure, the open-circuit potential of the stainless steel electrode in the simulated cooling water is approximately -210 mV. Further addition of 5 g / L of manganese dioxide particles to the simulated cooling water, which are then deposited on the surface of the stainless steel electrode, results in a rapid positive shift of the open-circuit potential to 521 mV. Figure 1 Curve 2) exceeded the pitting potential in simulated cooling water. Figure 1 Curve 4) leads to pitting corrosion. Repeating the above experiment, but before adding manganese dioxide, adding the pitting corrosion inhibitor containing 10 mg / L of sulfur ions from Example 1 to the cooling water, it was found that the open circuit potential of the stainless steel also showed a positive shift, but the magnitude of the positive shift was smaller. Figure 1 The middle curve (3) did not exceed the pitting potential of stainless steel in the simulated cooling water. Figure 1 (Curve 4) This shows that the pitting corrosion inhibitor effectively suppressed the positive shift of the open circuit potential of stainless steel in manganese dioxide-containing cooling water, making it lower than the pitting potential of stainless steel, thereby inhibiting pitting corrosion of stainless steel.

[0045] Electrochemical impedance spectroscopy (EIS) measurements of the stainless steel electrode were performed under the above three conditions, and the results are shown in the figure. Figures 2-3 . Figure 2 The results show that stainless steel has a large impedance value in simulated cooling water and a large capacitive arc radius in the Nyquist plot; the capacitive arc radius decreases significantly when manganese dioxide is deposited on the stainless steel surface, but increases significantly when pitting inhibitor is present. Figure 3 The Bode plot shows the |Z| of stainless steel in simulated cooling water. 0.01 The value is 59.39 kΩ·cm 2 It is in a passivated state. Figure 4 (a)); In simulated cooling water containing manganese dioxide, the |Z| of stainless steel 0.01 The value decreased to 0.095 kΩ·cm 2 Pitting corrosion appeared on the stainless steel surface. Figure 4 (b)); In simulated cooling water containing manganese dioxide and with added pitting inhibitors, the |Z| of stainless steel 0.01 The value increased to 42.69 kΩ·cm 2 It is also in a passivated state. Figure 4 (c) Pitting corrosion of stainless steel electrodes caused by manganese dioxide was effectively controlled.

[0046] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. The application of a pitting inhibitor for suppressing pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The pitting inhibitor contains sulfides and surfactants. In the pitting inhibitor, the concentration of sulfides, calculated as sulfide ions, ranges from 1 to 20 mg / L; the concentration of surfactants ranges from 40 to 60 mg / L. The pitting inhibitor was used in industrial cooling water.

2. The application of the pitting inhibitor according to claim 1 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The sulfide is soluble in water and produces sulfur ions.

3. The application of the pitting inhibitor according to claim 1 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The surfactant can form an adsorption film on the stainless steel surface.

4. The application of the pitting inhibitor according to claim 1 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The method for preparing the pitting inhibitor includes: first adding a surfactant to water, then adding a sulfide, stirring and dissolving to obtain the pitting inhibitor.

5. The application of the pitting inhibitor according to claim 4 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, Preparation was carried out at room temperature.

6. The application of the pitting inhibitor according to claim 4 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The stirring time is 1 to 20 minutes.

7. The application of the pitting inhibitor according to claim 1 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The cooling water contains manganese microorganisms.

8. The application of the pitting inhibitor according to claim 1 for inhibiting pitting corrosion of stainless steel in manganese dioxide-containing cooling water, characterized in that, The pitting corrosion is caused by the deposition of manganese dioxide in the cooling water on the stainless steel surface.

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