CN109457242B - Chromium-free passivator and preparation method and application thereof - Google Patents

Chromium-free passivator and preparation method and application thereof Download PDF

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CN109457242B
CN109457242B CN201811558903.6A CN201811558903A CN109457242B CN 109457242 B CN109457242 B CN 109457242B CN 201811558903 A CN201811558903 A CN 201811558903A CN 109457242 B CN109457242 B CN 109457242B
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chromium
free passivator
aluminum salt
manganese
passivation
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CN109457242A (en
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曹占芳
逯菲
钟宏
王帅
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/40—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing molybdates, tungstates or vanadates

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Abstract

The invention relates to a chromium-free passivator and a preparation method and application thereof. The pH value of the chromium-free passivator is 1-4.5, and the chromium-free passivator comprises: solvent water and soluble aluminum salt, wherein the mass concentration of the soluble aluminum salt is 0.05-2% by mass percent. The passivating agent can form a passivating film layer on the surface of the metal manganese, and the passivating film layer has good binding force and excellent corrosion resistance. The invention also provides a preparation method of the chromium-free passivator, which comprises the following steps: according to the mass percent, 0.05-2% of aluminum salt is added into solvent water and stirred to be dissolved to obtain a solution, and then the pH value of the solution is adjusted to 1-4.5 to obtain the chromium-free passivator. The invention also discloses the application of the chromium-free passivator or prepared by the preparation method of the chromium-free passivator in passivation of metal manganese.

Description

Chromium-free passivator and preparation method and application thereof
Technical Field
The invention relates to the field of corrosion prevention of manganese metal, and particularly relates to a chromium-free passivator and a preparation method and application thereof.
Background
As an important metal element, the manganese metal is widely used in industry and has large demand, has very important strategic significance on the development of national economy, and is applied to various industries such as steel smelting, building industry, machinery, transportation and the like. The method for producing manganese metal in industry is mainly electrolytic method, but because the chemical potential of manganese metal is low, the surface of manganese metal which is just electrolyzed is very rough, and the contact area with air is large, so that the manganese metal is easy to be oxidized in the air to cause the corrosion of manganese metal, and the purity and the mechanical property of manganese metal are reduced. In order to ensure the commercial value and the service performance of the manganese metal, the passivation treatment of the newly electrolyzed manganese metal is a very important link. The passivation treatment can form a layer of passivation film on the surface of the manganese metal, and the corrosion resistance of the manganese metal is improved so as to ensure the storage and transportation of the manganese metal. The common potassium dichromate solution with the concentration of 3 percent is used for passivating the manganese metal in the industry, the process is simple, the cost is low, the bath solution is stable, and the obtained passivation film has the advantages of uniform color, good binding force, high corrosion resistance and good self-repairing capability. However, hexavalent chromium is a highly toxic and carcinogenic substance, and a large amount of chromium-containing wastewater and waste liquid are generated in the passivation process, which seriously harms the environment and human health. Because of the environmental protection problem, the use of the chromate passivation process is strictly limited in many countries at present, so that the development of a novel environment-friendly passivator for replacing chromate has a very important significance for the benign development of the electrolytic manganese industry.
At present, technologists are also actively developing novel electrolytic manganese chromium-free passivators. For example, patent CN103805979A discloses a chromium-free passivation solution for manganese metal, which mainly comprises phosphate, cosolvent, corrosion inhibitor and brightener, and has certain effect on passivation of manganese metal. However, due to the use of phosphoric acid, the passivation solution can generate a large amount of phosphorus-containing passivation waste liquid, which has certain harm to water, and the phosphorus content in the manganese metal product is easy to exceed the standard. Patent CN103834941A discloses an electrolytic manganese passivation solution using molybdate as main passivating agent and triethanolamine and hydroxyethylidene diphosphate as complexing agent. The corrosion resistance of the manganese metal treated by the passivation solution is similar to that of a product passivated by potassium dichromate, but the molybdate is expensive, and the cost is overhigh after the molybdate is used, so that the industrial application is not utilized. Patent CN107034456A discloses a metal manganese passivation solution using silicate as a film-forming agent and hydrogen peroxide or potassium permanganate as an oxidant. The process does not need water washing after passivation, and the product is dried at 60 ℃ for half an hour, the surface of the product passivated by the passivation solution is bright and has better corrosion resistance, but the quality of the electrolytic manganese metal product is reduced to a certain extent due to the increase of the silicon content in the product. In conclusion, the existing chromium-free passivation technology for metal manganese has the defects of phosphorus pollution, unstable passivation solution, poor product color, no self-repairability and the like, so that the development of a novel environment-friendly chromium-free passivator product with excellent performance is urgently needed.
Disclosure of Invention
The invention aims to provide a chromium-free passivator for metal manganese, which has the advantages of good passivation effect, environmental protection and good stability, and further provides a chromium-free passivator, and a preparation method and application thereof.
The chromium-free passivator is characterized by having a pH of 1-4.5, and comprising: solvent water and soluble aluminum salt, wherein the mass concentration of the soluble aluminum salt is 0.05-2% by mass percent.
Further, the hydrogen peroxide solution is also included, and the concentration of the hydrogen peroxide solution is 1-15 ml/L.
Preferably, the soluble aluminium salt comprises one or more of aluminium nitrate, aluminium sulphate, aluminium chloride, polyaluminium chloride and polyaluminium sulphate.
Further, the aluminum salt-containing paint also comprises a reinforcing agent, wherein the mass ratio of the reinforcing agent to the aluminum salt is 0.01-0.5: 1.
Preferably, the enhancer comprises one or both of a soluble cerium salt and a soluble molybdate salt.
Preferably, the soluble cerium salt comprises one or more of cerium nitrate, cerium sulfate, cerium chloride and ceric sulfate.
Preferably, the soluble molybdate comprises one or more of sodium molybdate, potassium molybdate, zinc molybdate, calcium molybdate and ammonium molybdate.
The invention also provides a preparation method of the chromium-free passivator, which comprises the following steps: according to the mass percent, 0.05-2% of aluminum salt is added into solvent water and stirred to be dissolved to obtain a solution, and then the pH value of the solution is adjusted to 1-4.5 to obtain the chromium-free passivator.
The invention also discloses the application of the chromium-free passivator or prepared by the preparation method of the chromium-free passivator in passivation of metal manganese.
Further, the application includes: and immersing the metal manganese into the chromium-free passivator for passivation for 30 seconds to 5 minutes.
Compared with the prior art, the invention has the advantages that: the pH value of the chromium-free passivator is 1-4.5, and the chromium-free passivator comprises: solvent water and soluble aluminum salt, wherein the mass concentration of the soluble aluminum salt is 0.05-2% by mass percent. The acidic passivating agent contains H+The active metal manganese acts on the surface of manganese with hydrogen ions to generate proper Mn2+Ions due to H+Causes the pH of the manganese metal surfaceIncrease, resulting in Al in the passivating agent3+Rapid Mn reaction with the surface of metal manganese2+The hydrotalcite-like compound passivation film layer is formed by crystallization, and the passivation film layer has good binding force and excellent corrosion resistance. The passivating agent provided by the invention does not contain carcinogenic or toxic substances such as hexavalent chromium and the like, has the characteristic of environmental friendliness, is cheap and easily available in comparison with other metal inorganic salts, and is beneficial to reducing the cost, so that the passivating agent has a good industrial application prospect.
In addition, the passivating agent of the invention adds a small amount of H2O2Can promote Mn required by the surface of the manganese metal in the application process2+And (4) generating.
In the present invention, the reinforcing agent used is one or both of a soluble cerium salt and a soluble molybdate salt, and is intended to further promote Al3+With Mn2+Forming a hydrotalcite-like compound passivation film layer. Wherein the soluble cerium salt, based on the difference in atomic radius, can react with Al under acidic conditions3+、Mn2+The hydrotalcite-like compound passivation film layers are cooperatively formed, and the passivation film layers are more compact and have better passivation performance; in addition, a small amount of H is added into the passivator in the application process2O2Ce in soluble cerium salts3+Can be substituted by H under acidic condition2O2Partial oxidation to Ce4+When the film layer is destroyed, Ce stored in the inorganic film4+The components can act with exposed fresh manganese metal to realize self-repair of the passivation film layer; in addition, the soluble molybdenum salts used, predominantly MoO in solution4 2-When Al is present in an anionic state3+、Mn2+、Ce3+When the hydrotalcite-like film layer is formed on the surface of electrolytic manganese metal by plasma, the MoO is based on the positive electricity characteristic of the hydrotalcite compound plate layer4 2-The hydrotalcite film layer is convenient to be intercalated between hydrotalcite layer layers, molybdenum salt precipitates are formed under the condition that the pH value of the manganese surface is relatively high, and the compactness and the passivation performance of the passivation film layer can be further improved.
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The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 is a Tafel plot of unpassivated manganese metal and passivated manganese metal prepared in example 5. Wherein: curve 1 is the Tafel curve of the unpassivated manganese metal; curve 2 is the Tafel curve for passivated manganese metal prepared in example 5.
FIG. 2 is a scanning electron micrograph of the unpassivated manganese metal.
FIG. 3 is a surface electron micrograph of passivated manganese metal prepared in example 5.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but rather should be construed as broadly as the present invention is capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
Example 1:
firstly, preparing an electrolytic manganese metal product in a diaphragm tank by an electrolytic method: stainless steel is used as a cathode plate, and a lead-silver four-alloy plate is used as an anode plate. The electrolysis conditions are as follows: 120g/L of ammonium sulfate, 76.9g/L of manganese sulfate and 0.05g/L of selenium dioxide, wherein the pH value of the catholyte is about 6.8-7.0, and the current density is 350A/m2And the electrolysis temperature is 38 ℃, the electrolysis time is 1.5h, and the prepared electrolytic manganese product is used for subsequent passivation experiments and passivation layer performance evaluation.
Preparing a passivating agent: 3g of aluminum nitrate, 5mLH g2O2(30%) was added to 1L of water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH 3.5, to obtain a chromium-free passivator (aluminum nitrate with a mass concentration of about 0) for electrolytic manganese metal surface treatment.3％)。
The pH value of the chromium-free passivator is 1-4.5, and the chromium-free passivator comprises: 1L of water, 3g of aluminum nitrate and 5mLH2O2(30%), wherein the mass concentration of the aluminum nitrate is about 0.3% by mass.
Passivation and performance detection of electrolytic manganese products: and (3) placing the prepared chromium-free passivator in a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate in the passivation tank, immersing the surface of the cathode plate with the chromium-free passivator, passivating for 1 minute, taking out, washing with distilled water, and drying to obtain a passivated manganese metal product. Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 2.020 multiplied by 10-9A/cm2。
Example 2:
the electrolytic manganese metal product was prepared as in example 1.
Preparing a passivating agent: 3g of aluminum nitrate was added to 1L of water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH 3.5, to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (aluminum nitrate concentration by mass is about 0.3%).
The pH value of the chromium-free passivator is 3.5, and the chromium-free passivator comprises 3g of aluminum nitrate and 1L of water; wherein the mass concentration of the aluminum nitrate is about 0.3% by mass percentage.
Passivation and performance detection of electrolytic manganese products: and (3) placing the prepared chromium-free passivator in a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate in the passivation tank, immersing the surface of the cathode plate with the chromium-free passivator, passivating for 1 minute, taking out, washing with distilled water, and drying to obtain a passivated manganese metal product. Electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 9.521 multiplied by 10-9A/cm2。
Example 3:
the electrolytic manganese metal product was prepared as in example 1.
Preparing a passivating agent: 3g of aluminum nitrate, 0.3g of cerium nitrate and 5mLH g of cerium nitrate2O2(30%) additionThe solution is stirred and dissolved in 1L of water, and then sulfuric acid is added to adjust the pH value of the solution to be 3.5, so that the chromium-free passivator for electrolytic manganese metal surface treatment is prepared.
The pH value of the chromium-free passivator is 3.5, and the chromium-free passivator comprises 3g of aluminum nitrate, 0.3g of cerium nitrate and 5mLH2O2(30%) and 1L water; wherein, the mass concentration of the aluminum nitrate is about 0.3 percent and the mass concentration of the cerium nitrate is about 0.03 percent in percentage by mass.
Passivation and performance detection of electrolytic manganese products: and (3) placing the chromium-free passivator in a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate in the passivation tank, immersing the surface of the cathode plate with the chromium-free passivator, passivating for 1 minute, taking out, washing with distilled water, and drying to obtain a passivated manganese metal product. Electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 8.024 multiplied by 10-10A/cm2。
Example 4:
the electrolytic manganese metal product was prepared as in example 1.
Preparing a passivating agent: 3g of aluminum nitrate, 0.3g of sodium molybdate and 5mLH g of sodium molybdate2O2(30%) was added to 1L of water to dissolve with stirring, and then the solution was adjusted to pH 3.5, to prepare a chromium-free passivator for electrolytic manganese metal surface treatment.
The pH value of the chromium-free passivator is 3.5, and the chromium-free passivator comprises 3g of aluminum nitrate, 0.3g of sodium molybdate and 5mLH2O2(30%) and 1L water; wherein, the mass concentration of the aluminum nitrate is about 0.3 percent and the mass concentration of the cerium nitrate is about 0.03 percent in percentage by mass.
Passivation and performance detection of electrolytic manganese products: and (3) placing the chromium-free passivator in a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate in the passivation tank, immersing the surface of the cathode plate with the chromium-free passivator, passivating for 1 minute, taking out, washing with distilled water, and drying to obtain a passivated manganese metal product. Electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 1.542 multiplied by 10-10A/cm2。
Example 5:
the electrolytic manganese metal product was prepared as in example 1.
Preparing a passivating agent: 3g of aluminum nitrate, 0.3g of cerium nitrate, 0.2g of sodium molybdate and 5mL of H2O2(30%) was added to 1L of water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH 3.5, to obtain a chromium-free passivator for electrolytic manganese metal surface treatment (mass concentration about 0.35%).
The pH value of the chromium-free passivator is 3.5, and the chromium-free passivator comprises 3g of aluminum nitrate, 0.3g of cerium nitrate, 0.2g of sodium molybdate and 5mLH2O2(30%) and 1L water; wherein, the mass concentration of the aluminum nitrate is about 0.3 percent and the mass concentration of the cerium nitrate is about 0.03 percent in percentage by mass.
Passivation and performance detection of electrolytic manganese products: and (3) placing the prepared chromium-free passivator in a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate in the passivation tank, immersing the surface of the cathode plate with the chromium-free passivator, passivating for 1 minute, taking out, washing with distilled water, and drying to obtain a passivated manganese metal product. Electrochemical performance tests were performed on the unpassivated manganese metal and the passivated manganese metal, and the results of the polarization curves are shown in fig. 1 and table 1.
TABLE 1 Tafel Curve results for non-passivated manganese metal products and passivated manganese metal products
Sample (I) Self-corroding potential (V) Self-corrosion current (A/cm)2)
Non-passivated Mn -1.446 3.434×10-4
Post-passivation Mn -1.346 6.458×10-11
As shown in the attached figure 1 and the electrochemical test results in the table 1, after the manganese metal product is passivated, the self-corrosion potential of the product is obviously shifted forwards, the self-corrosion potential is shifted forwards by 0.10V, the corresponding self-corrosion current is reduced by more than six orders of magnitude, and the corrosion resistance of the electrolytic manganese metal product is obviously improved.
The electron microscope results before and after sample passivation are shown in the attached figures 2 and 3, wherein figure 2 is an electron microscope picture of an unpassivated manganese metal product after electrolysis is finished, and figure 3 is an electron microscope picture of a passivated manganese metal product. As can be seen from FIG. 2, the manganese metal product just electrolyzed has smooth conical surface; it can be seen from fig. 3 that the surface of the passivated manganese metal product is obviously covered by a passivation film layer.
Example 6:
the electrolytic manganese metal was prepared as in example 1.
Preparing a passivation solution: 3g of aluminum sulfate, 0.5g of cerium nitrate and 10mLH g of cerium nitrate2O2(30%) was added to 1L of water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH 2, to prepare a chromium-free passivation solution for electrolytic manganese metal surface treatment.
The pH value of the chromium-free passivator is 2, and the chromium-free passivator comprises 3g of aluminum sulfate, 0.5g of cerium nitrate and 10mLH2O2(30%) and 1L water; wherein, the mass concentration of the aluminum nitrate is about 0.3 percent and the mass concentration of the cerium nitrate is about 0.05 percent in percentage by mass.
Passivation and performance detection of electrolytic manganese products: placing the chromium-free passivation solution into a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate into the passivation tank to ensure that the chromium-free passivation solution immerses the surface of the cathode plate, taking out the cathode plate after passivation for 1 minute, washing the cathode plate with distilled water, and drying to obtain the cathode plateTo the passivated manganese metal product. Electrochemical performance test of passivated manganese metal shows that the self-corrosion potential is-1.383V and the self-corrosion current is 1.802 multiplied by 10-10A/cm2And the passivation effect is good.
Example 7:
the electrolytic manganese metal was prepared as in example 1.
Preparing a passivation solution: 3g of aluminum chloride, 0.5g of ammonium molybdate, 8mLH2O2(30%) was added to 1L of water to dissolve it with stirring, and then the solution was adjusted to pH 2 to prepare a chromium-free passivation solution for electrolytic manganese metal surface treatment.
The pH value of the chromium-free passivator is 2, and the chromium-free passivator comprises 3g of aluminum chloride, 0.5g of ammonium molybdate and 8mLH2O2(30%) and 1L water; wherein, the mass concentration of the aluminum nitrate is about 0.3 percent and the mass concentration of the cerium nitrate is about 0.05 percent in percentage by mass.
Passivation and performance detection of electrolytic manganese products: and (3) placing the chromium-free passivation solution into a passivation tank, washing the surface of the electrolytic cathode plate with clear water, then placing the cathode plate into the passivation tank, immersing the surface of the cathode plate with the chromium-free passivation solution, passivating for 1 minute, taking out the cathode plate, washing with distilled water, and drying to obtain a passivated manganese metal product. Electrochemical performance tests are carried out on the passivated manganese metal, and the results show that the self-corrosion potential is-1.219V, and the self-corrosion current is 1.965 multiplied by 10-10A/cm2And the passivation effect is good.
As can be seen from examples 1 to 7, the self-corrosion current of the electrolytic manganese metal can be controlled from 3.434 multiplied by 10 under the acidic condition by singly adopting the soluble aluminum salt as the electrolytic manganese passivator-4Reduced to 9.521 × 10-9A/cm2(example 2), the self-corrosion current decreased by 4 orders of magnitude or more, indicating that the aluminum salt reacts with Mn on the surface of manganese under acidic conditions2+The formed passivation film is excellent. By H2O2The components such as soluble cerium salt, soluble molybdenum salt and the like are added into the passivator to further improve the passivation performance of the passivator, and the self-corrosion current can be further reduced to 6.458 multiplied by 10-11(reduced by more than 6 orders of magnitude), the performance is very good.
Compared with the prior art, the invention has the following other beneficial effects:
the main component of the chromium-free passivation solution is soluble aluminum salt, compared with chromate, hexavalent chromium is not used in the passivation process, and the pollution to the environment and the harm to the health of a human body are greatly reduced.
Compared with phosphate and silicate, the passivated product does not have the condition that the content of phosphorus or silicon exceeds the standard, and the use value of the manganese metal is improved; particularly, elements such as aluminum and the like used in the invention are beneficial components in the subsequent application process of the manganese metal; for example, aluminum or aluminum-containing agents are used as deoxidizing and nitrogen-fixing agents in steel making, the crystal grains are refined, the aging of low-carbon steel is inhibited, the toughness of the steel at low temperature is improved, and the brittle transition temperature of the steel is particularly reduced; improve the oxidation resistance of the steel.
The invention adopts an acidic system with pH of 1-4.5, and Al is used as an Al element under an acidic condition3+The form exists. Active metal manganese and H+And H2O2Act on the surface to generate a proper amount of Mn2+，Mn2+Under the environment that the pH of the surface of the metal manganese is locally increased, the metal manganese is easy to react with Al3+、Ce3+And the trivalent metal ions are assembled into a compact hydrotalcite-like protective film, and the film layer is seamlessly combined with the surface of the metal manganese, so that an ideal passivation effect is achieved.
(4) The reinforcing agent used in the chromium-free passivation solution is soluble cerium salt or soluble molybdate, and the cerium salt and the molybdate can further improve the compactness of the passivation film layer and improve the passivation effect on the basis of forming a hydrotalcite-like passivation film by aluminum salt.
(5) The chromium-free passivation solution has the advantages of good passivation effect and stability, good environmental protection and low cost through the synergistic effect of the aluminum salt and the reinforcing agent. Compared with the self-corrosion potential of the manganese metal product before passivation, the self-corrosion potential after passivation is shifted by more than 0.10V, and the corresponding self-corrosion current is reduced by more than six orders of magnitude.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

Claims (7)

1. The chromium-free passivator for the metal manganese is characterized by having a pH value of 1-4.5, and being composed of sulfuric acid, solvent water and soluble aluminum salt, or sulfuric acid, solvent water, soluble aluminum salt and hydrogen peroxide, or sulfuric acid, solvent water, soluble aluminum salt, hydrogen peroxide and a reinforcing agent, or sulfuric acid, solvent water, soluble aluminum salt and a reinforcing agent; wherein the mass concentration of the soluble aluminum salt is 0.05-2% by mass percent; the concentration of the hydrogen peroxide is 1-15 ml/L; the mass ratio of the reinforcing agent to the aluminum salt is 0.01-0.5: 1, and the reinforcing agent is one or two of soluble cerium salt and soluble molybdate.
2. The chromium-free passivator for metal manganese of claim 1, wherein the soluble aluminum salt comprises one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, polyaluminum chloride, and polyaluminum sulfate.
3. The chromium-free passivator for manganese metal of claim 1 wherein the soluble cerium salt comprises one or more of cerium nitrate, cerium sulfate and cerium chloride.
4. The chromium-free passivator for manganese metal of claim 1 wherein the soluble molybdate comprises one or more of sodium molybdate, potassium molybdate, zinc molybdate, calcium molybdate, and ammonium molybdate.
5. The method for preparing the chromium-free passivator for manganese metal according to any one of claims 1 to 4, comprising: adding soluble aluminum salt, or soluble aluminum salt and hydrogen peroxide, or soluble aluminum salt, hydrogen peroxide and a reinforcing agent, or soluble aluminum salt and reinforcing agent into solvent water, stirring and dissolving to obtain a solution, and then adding sulfuric acid to adjust the pH of the solution to 1-4.5 to obtain the chromium-free passivator; wherein the mass concentration of the soluble aluminum salt is 0.05-2% by mass; the concentration of hydrogen peroxide is 1-15 ml/L; the mass ratio of the reinforcing agent to the soluble aluminum salt is 0.01-0.5: 1.
6. The use of a chromium-free passivator for manganese metal as defined in any one of claims 1 to 4 or a chromium-free passivator prepared by the method of preparation of a chromium-free passivator for manganese metal as defined in claim 5 for passivating manganese metal.
7. The application according to claim 6, wherein the application comprises: and immersing the metal manganese into the chromium-free passivator for passivation for 30 seconds to 5 minutes.
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