CN101967643A - Application of chitosan used as brass corrosion inhibitor - Google Patents

Abstract

The invention discloses an application of chitosan (CTS) used as a brass corrosion inhibitor, belonging to the technical fields of corrosion and protection of metal materials. The concentration of the CTS in the HCL solution of 0.1mol/L is 0-1.5g/L. The electrochemical data show that when the CTS is used as a brass corrosion inhibitor in the HCL solution of 0.1mol/L, the CTS has better corrosion inhibition effect; and especially, after the corrosion inhibitor CTS of 1.0g/L is added into the HCL solution of 0.1mol/L, the corrosion current of the brass is obviously reduced from 11.54mu A/cm<2> to 5.76mu A/cm<2>, and the corrosion inhibition efficiency is 54.08%. Thus, the results prove that the CTS can be used as the brass corrosion inhibitor, is a natural high molecular organic matter, has the advantages of rich resources, no toxicity and harm, easy biological degradation and the like, and has better corrosion inhibition effect on the brass in the system after being used.

Description

Application of Chitosan as Corrosion Inhibitor for Brass

technical field

The invention relates to the application of chitosan as a corrosion inhibitor for brass, belonging to the technical field of metal material corrosion and protection.

Background technique

Brass is a binary alloy composed of copper and zinc. Brass is widely used in heat exchangers, condensers, cryogenic pipelines and submarine transportation pipes because of its good mechanical properties, process properties, electrical and thermal conductivity and corrosion resistance. However, during the operation of the equipment, some components in the medium are often deposited on the surface of the equipment or pipelines, which reduces the heat exchange efficiency, and chemical cleaning with acid cleaning agents is required, among which hydrochloric acid is the most widely used cleaning agent. During the cleaning process, brass is very prone to corrosion, which leads to the failure of equipment perforation, often causing huge economic losses. Therefore, the problem of corrosion inhibition of brass in hydrochloric acid medium is particularly important.

Adding corrosion inhibitors to cleaning agents can not only effectively control corrosion, but also not destroy the original process flow, almost no additional equipment is required, and it has the characteristics of economy, high efficiency, and strong applicability, and has been widely used. With the deterioration of the earth's environment and the enhancement of human awareness of environmental protection, the development of environmentally friendly green corrosion inhibitors has become an important sustainable development measure. At present, most pickling corrosion inhibitors are organic compounds containing nitrogen, sulfur, oxygen, and phosphorus, such as benzotriazole, 2-mercaptobenzothiazole, and propynyl alcohol. However, a serious disadvantage of this class of corrosion inhibitors is that they are toxic and most of them are not biodegradable. The present invention proposes a kind of brass anticorrosion corrosion inhibitor-chitosan just in order to solve this problem.

Chitosan (chitosan, CTS) is a linear type of natural polymer organic matter (as shown below),

The chemical name is (1,4)-2-amino-2-deoxy-β-D-glucan, which is very rich in resources and mainly obtained by deacetylation of chitin. It is non-toxic, harmless, and easy to biodegrade. Containing active groups such as -OH and _-NH2 in the molecule, it has high chemical activity and is prone to hydrolysis, carboxylation, crosslinking and other reactions to obtain new structures and properties. The molecular structure of chitosan (CTS) contains a large number of amino and hydroxyl groups of organic corrosion inhibitors, which can coordinate with metal elements, firmly adsorb on the metal surface, and form a protective film to prevent metal corrosion. Chitosan has a certain corrosion inhibition effect, and it is environmentally friendly and cheap. It has high application value to develop it as an independent corrosion inhibitor or an effective component of a compound corrosion inhibitor. However, as an environment-friendly corrosion inhibitor, chitosan has not been reported on the corrosion inhibition of brass in 0.1mol/L HCl solution.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the brass anti-corrosion corrosion inhibitor in the prior art, and provide a new environment-friendly brass anti-corrosion corrosion inhibitor.

Technical scheme of the present invention

Application of chitosan as corrosion inhibitor for brass corrosion protection.

The concentration of chitosan in 0.1mol/L HCl solution is 0.005-1.5g/L.

Chitosan has the best corrosion inhibition effect on brass when the concentration of chitosan in 0.1mol/L HCl solution is 1.0g/L.

Beneficial effects of the present invention

A brass anti-corrosion and corrosion inhibitor of the present invention is a green water treatment agent, which participates in the carbon and nitrogen cycle of the ecological system after biodegradation, plays an important role in regulating the earth's ecological environment, has no harm to the environment, and is in line with sustainable The needs of the development concept, and the raw materials are easy to get. Electrochemical data show that chitosan is used as brass corrosion inhibitor in 0.1mol/L HCl solution has better corrosion inhibition effect, especially when 1.0g/L corrosion inhibitor chitosan is added in 0.1mol/L HCl solution After adding sugar, the corrosion current of brass decreased significantly from 11.54μA/cm ² to 5.76μA/cm ² , and the corrosion inhibition efficiency was 54.08%.

Description of drawings

Figure 1. Nyquist plots of brass electrodes soaked in 0.1mol/L HCl solution without and with different concentrations of chitosan for 0.5h

Figure 2. Polarization curves of brass electrodes soaked in 0.1mol/L HCl solution without and with different concentrations of corrosion inhibitor chitosan for 0.5h

Detailed ways

The present invention will be further elaborated below by means of embodiments in conjunction with the accompanying drawings, but the present invention is not limited.

Example 1

1. Solution preparation

Chitosan (BR): The degree of deacetylation is 80.0-95.0%, white powder, and the implementation system is 0.1mol/L HCl solution.

All the utensils used in the experiment were washed with deionized water, and all the solutions used were prepared with deionized water.

2. Brass electrodes

The non-working surface of the brass electrode is sealed with epoxy resin, and the working area is 1.0cm ² . The surface before measurement is polished and polished step by step with 1#, 3#, 5# metallographic sandpaper, rinsed with deionized water, and deionized with absolute ethanol. Oil, rinsed with deionized water, put into the electrolytic cell and stabilized for 30 minutes before testing.

3. Test method

AC Impedance and Polarization Curve Test

The classic three-electrode system is adopted, and the working electrode is a brass electrode. The auxiliary electrodes used are all platinum electrodes, the reference electrodes are all saturated calomel electrodes (SCE), and the potentials shown in the present invention are all relative to the saturated calomel electrodes.

The equipment used for the determination of AC impedance and polarization curves was Shanghai Chenhua Electrochemical Workstation CHI660C. The frequency range of AC impedance measurement was 100.00kHz-50.00mHz, the AC excitation signal was 10mV, and the scanning rate of polarization curve was 1mV/s.

In the measurement of AC impedance, the blank means that 0.1mol/L HCl solution is used as the medium, and the addition amount of corrosion inhibitor is 0mg/L.

Accompanying drawing 1 is the Nyquist diagram after brass electrode does not add and adds the 0.1mol/LHCl solution of different concentrations of corrosion inhibitor chitosan soaked 0.5h, wherein curve 1, curve 2, curve 3, curve 4, curve 5 , Curve 6 and Curve 7 represent the Nyquist diagrams for CTS of 0g/L, 0.005g/L, 0.05g/L, 0.1g/L, 0.5g/L, 1.0g/L, and 1.5g/L, respectively. When there is a corrosion inhibitor in the solution, the corrosion inhibitor interacts with the metal to form a protective film, reflecting the corrosion inhibition effect. The corresponding AC impedance test result is an impedance spectrum (Nyquist diagram), and the impedance spectrum is an irregular capacitive reactance arc, indicating that the corrosion of brass in the studied system is mainly controlled by charge transfer. The arc and the chord length on the Z axis correspond to the film resistance R _f of the brass electrode. The larger the R _f is, the better the corrosion inhibition effect is.

It can be seen from Figure 1 that compared with the blank solution, the chord length of the impedance spectrum corresponding to the brass electrode added with CTS corrosion inhibitor increased significantly, but when the CTS exceeded 1.0g/L, the chord length of the impedance spectrum showed a downward trend, and the copper electrode The corrosion resistance performance of the steel is reduced instead. Therefore, when the CTS concentration is 1.0g/L, the corrosion inhibition effect is the best.

It has been found that CTS has good corrosion inhibition ability for brass in 0.1mol/L HCl solution by AC impedance method, and the optimal concentration of CTS as a corrosion inhibitor has been obtained.

Accompanying drawing 2 is the polarization curve figure after brass electrode is soaked 0.5h in the 0.1mol/LHCl solution that does not add and adds different concentrations of corrosion inhibitor chitosan, wherein curve 1, curve 2, curve 3, curve 4, Curve 5, Curve 6 and Curve 7 respectively indicate that the CTS is 0g/L, 0.005g/L, 0.05g/L, 0.1g/L, 0.5g/L, 1.0g/L, 1.5g/L polarization curves, The corresponding corrosion potential and corrosion current density data are shown in Table 1. The corrosion inhibition efficiency (η%) of the corrosion inhibitor is calculated according to the following formula:

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; I</span>}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>$

I ₀ and I are the corrosion current densities of the blank experiment and after adding the corrosion inhibitor, respectively.

Table 1 Electrochemical parameters of brass in 0.1mol/L HCl solution with different concentrations of CTS

It can be seen from Table 1 that when the corrosion inhibitor CTS is not added to the 0.1mol/L HCl solution, the corrosion current of the brass electrode is 11.54μA/cm ² , and the corrosion current becomes smaller with the addition of the corrosion inhibitor. When the CTS concentration is 1.0 g/L, the minimum corrosion current of copper electrode is 5.76μA/cm ² , and the corresponding corrosion inhibition efficiency is also the highest, which is 54.1%, indicating that CTS has a good corrosion inhibition effect on brass in 0.1mol/L HCl solution . This is consistent with the conclusion obtained by the AC impedance method. In addition, it can also be seen from the polarization curve that the corrosion potential and cathodic polarization curve of the brass electrode shifted negatively after adding the corrosion inhibitor CTS, indicating that the corrosion inhibitor is a cathodic corrosion inhibitor.

The above content is only a basic description of the concept of the present invention, and any equivalent transformation made according to the technical solution of the present invention shall fall within the scope of protection of the present invention.

Claims (3)

1. The application of chitosan as a corrosion inhibitor for brass corrosion. 2. the application of chitosan as claimed in claim 1 as brass corrosion inhibitor, is characterized in that described application is that the concentration of chitosan is 0.005～1.5g/L in 0.1mol/LHCl solution. 3. the application of chitosan as claimed in claim 1 as brass corrosion inhibitor, is characterized in that described application is that the concentration of chitosan is 1.0g/L in 0.1mol/LHCl solution.

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