CN115323365A

CN115323365A - Chromium-free passivation method for electrolytic manganese

Info

Publication number: CN115323365A
Application number: CN202110503942.1A
Authority: CN
Inventors: 曹占芳; 雷思华; 钟宏; 王帅; 马鑫
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2021-05-10
Filing date: 2021-05-10
Publication date: 2022-11-11
Anticipated expiration: 2041-05-10
Also published as: CN115323365B

Abstract

The invention relates to the technical field of electrolytic manganese passivation, in particular to a chromium-free passivation method of electrolytic manganese, which is characterized in that electrolytic manganese obtained by electrolysis is directly placed in a high-aluminum passivation solution for passivation without being cleaned; the high-aluminum passivation solution is an aluminum salt homogeneous aqueous solution; wherein the mass percent concentration of the aluminum salt is greater than 2.0wt.%. The research of the invention finds that the adverse effect of ammonium sulfate remained in electrolytic manganese on passivation can be effectively solved through the action of high aluminum salt concentration, and the effective passivation of manganese can be realized on the premise of not washing out ammonium sulfate.

Description

Chromium-free passivation method for electrolytic manganese

Technical Field

The invention relates to the field of corrosion prevention of metal manganese, in particular to a passivation method of electrolytic manganese, especially electrolytic manganese with residual ammonium sulfate.

Background

Manganese has very important strategic significance on the development of national economy, the high-quality manganese with the average manganese content of 35 percent per year produced by global manganese mine plants reaches 600 ten thousand tons, and the manganese alloy yield reaches about 800 ten thousand tons. The preparation method of manganese metal is generally divided into two methods of preparing manganese by a fire method and preparing manganese by a wet method, and the two methods both use pyrolusite and rhodochrosite as main raw materials. The fire method is less and less applied in industry, and the wet method mainly refers to the electrolytic method for preparing manganese. The manganese metal prepared by the electrolytic method has low impurity content and high product purity, is the most important preparation method for industrially producing manganese metal at present, wherein the annual output of electrolytic manganese in 2014 in China already accounts for 98.5 percent of the world yield of electrolytic manganese.

It is known that different metals have different electrolytic behaviors and different electrolytic preparation methods, and for example, in manganese electrolysis, it is generally necessary to add ammonium sulfate (70 to 150 g/L) at a high concentration as an electrolytic aid to an electrolyte solution in order to perform metal manganese electrodeposition. The use of ammonium sulphate contributes to improving the effect of manganese electrolysis, mainly in that: (1) The conductivity of the solution is improved, so that the voltage of the battery is reduced, and the energy consumption is reduced. (2) Plays a role in pH buffering capacity and formation of a manganese-ammonia complex, and prevents hydroxyl and oxide of manganese from precipitating on the surface of the cathode in neutral or weakly alkaline solution. Meanwhile, in the production of manganese by electrolysis, electrolytic manganese is obtained by electrolytic deposition onto the cathode plate. The stripped electrolytic manganese is in an irregular shape with one side contacting the cathode plate being bright and the other side being rough. The rough surface has a large surface area due to rich dendritic structures, so that electrolytic manganese just electrolyzed out of the cell is very easy to contact with air to be oxidized and corroded, the purity and the performance of a manganese product are reduced, and the simple substance manganese needs to be passivated immediately after being electrolyzed.

Currently, many documents or patents have been reported about the process optimization and surface passivation of electrolytic manganese, such as: goddard in the presence of trace amounts of SO ₂ And SeO ₂ 0.0015 to 0.015 percent of water-soluble polyacrylamide is added into the electrolyte, so that thick, compact and high-quality metal manganese is obtained, the deposition period is prolonged by about 70 percent, and the utilization rate of manganese is improved under the condition of maintaining high current efficiency. The patent CN101824615A adopts sodium silicate and titanium inorganic salt to form a chromium-free passivator for electrolytic manganese, and the passivation process is simple and convenient, and has no toxicity or pollution to the environment. Zou Xing and the like research on electrolytic manganese cleaning passivatorHas no toxicity, can be directly discharged into the environment, and can be completely decomposed and volatilized under the condition of slightly higher temperature, and does not bring any impurities to the electrolytic manganese product.

In addition, the inventor discloses that 0.05-2% of aluminum salt is used as a passivation agent of Mn in Chinese patent with publication No. CN109457242A, so that a Mn-Al hydrotalcite passivation layer is formed on the surface of electrolytic manganese, and effective passivation of manganese is realized. The present inventors have intensively studied and found that the main cause of the deterioration of the industrial amplification effect is the residue of ammonium sulfate in the electrolytic manganese process. After long-time electrolysis, ammonium sulfate is easy to crystallize and separate out on the upper end boundary and the surface of the electrode plate, so that the later passivation process is influenced, and the existence of the ammonium sulfate can generate adverse effect on the passivation process and reduce the passivation effect. The effect of ammonium sulfate on passivation at the laboratory stage is small and can easily be neglected, but the residual negative effect after industrial scale-up is further highlighted. However, the industry does not disclose any technical problem that ammonium sulfate influences the passivation effect of the Mn-Al hydrotalcite, and does not suggest related solutions.

Disclosure of Invention

In order to solve the technical problem that the passivation effect of Mn-Al hydrotalcite is not ideal due to ammonium sulfate remained in the manganese electrolysis process, the invention provides a chromium-free passivation method of electrolytic manganese, and aims to solve the technical problem of poor passivation effect due to ammonium sulfate.

The inventor of the invention has found through intensive research that 70-150 g/L ammonium sulfate is generally adopted in electrolytic manganese electrolytic systems, so that a large amount of ammonium sulfate is inevitably remained on the surface of electrolytic manganese when electrolytic manganese is taken out of a tank, and the influence of the remained ammonium sulfate on the passivation effect of the traditional chromium salt is not large, however, if an aluminum-based passivation system is adopted, part of the ammonium sulfate remained on the surface in the construction of a low-concentration aluminum-based passivation film layer is remained in the passivation film layer, so that pitting corrosion of a Mn-Al hydrotalcite film layer is caused, and the corrosion resistance of the aluminum-based passivation film is further continuously reduced; the adverse effect is not obvious in the laboratory bench stage and can be ignored easily, but is obvious in the industrial scale-up stage. The inventor firstly discovers the technical problem of the construction of the Mn-Al hydrotalcite passivation layer by ammonium sulfate remained in electrolytic manganese and provides the following solutions:

a chromium-free passivation method of electrolytic manganese is characterized in that electrolytic manganese obtained by electrolysis is directly placed in a high-aluminum passivation solution for passivation without being cleaned;

the high-aluminum passivation solution is an aluminum salt homogeneous aqueous solution; wherein the mass percent concentration of the aluminum salt is greater than 2.0wt.%.

Aiming at the technical problem of unsatisfactory passivation effect caused by the existence of ammonium sulfate residue in the passivation process of Mn-Al of electrolytic manganese, the invention innovatively discovers that the negative effect of the residual ammonium sulfate on the passivation layer can be effectively solved and good passivation effect can be obtained by adopting the high-concentration aluminum salt passivator.

The research of the invention finds that under the condition of the high-concentration aluminum-based passivator, the residual ammonium ions on the surface can be fully utilized as the oxidant (H) in the construction process of the passivation layer film layer ⁺ ) The method has the advantages that the method participates in the construction of the film layer, ammonium ions on the surface can be completely consumed under the condition of a high-concentration passivation system, the ammonium ions cannot remain in the passivation film layer, the formed passivation film layer is more compact, no pitting corrosion occurs in the later period, and the passivation performance is more excellent; the invention solves the problem that the corrosion resistance is reduced because the low-concentration aluminum-based passivation film layer is easily influenced by ammonium ions, and simultaneously reduces the acid consumption to a certain extent.

According to the invention, the electrolytic manganese obtained by electrolysis is directly placed in the passivation system with the concentration of aluminum salt for passivation without being cleaned, so that the problems that the residual ammonium sulfate influences the construction of the Mn-Al passivation layer and the pitting corrosion of the passivation layer can be effectively solved, the treatment process can be simplified, and the problems of hydrolysis and oxidation etching of the electrolytic manganese newly taken out of the tank in the washing process can be avoided.

Preferably, the electrolytic manganese is electrolytic manganese with residual ammonium sulfate;

preferably, the residual amount of ammonium sulfate in the electrolytic manganese is 0.05 to 20wt.%.

In the present invention, the electrolytic manganese may be prepared based on a technique known in the industry, for example, the electrolytic manganese is obtained by electrolysis in an electrolyte containing ammonium sulfate and manganese sulfate.

The concentrations of ammonium sulfate and manganese sulfate and the electrolysis process are well known in the industry.

In the invention, the aluminum salt passivation system and the accurate control of the aluminum salt concentration are key points for solving the negative influence of ammonium sulfate on the Mn-Al passivation layer and improving the passivation effect.

In the invention, the aluminum salt is one or more of aluminum citrate, aluminum acetate, aluminum sulfate, aluminum chloride, aluminum nitrate, polyaluminum chloride and polyaluminum sulfate.

Preferably, in the high-aluminum passivation solution, the mass percentage concentration of the aluminum salt is 2.5-45 wt.%; more preferably from 3.0 to 5.0wt.% or from 10.0 to 40.0wt.%. It was found that controlling the concentration of the aluminium salt at this preferred concentration surprisingly further addresses the effect of ammonium sulphate on electrolytic manganese passivation and contributes to further improving the passivation effect.

In the invention, the high-aluminum passivation solution also contains acid.

Preferably, the acid is one or more of nitric acid, sulfuric acid, hydrochloric acid, citric acid and acetic acid.

Preferably, the pH value of the high-aluminum passivation solution is 1.0-5.5; more preferably 2.0 to 4.5.

Preferably, a reinforcer is also added into the high-aluminum passivation solution;

the reinforcing agent is rare earth salt (RE) ³⁺ 、RE ⁴⁺ ) At least one water-soluble salt selected from molybdate, tungstate, silicate, titanate, nitrate, maleate, fumarate, borate, phytate, tartrate, citrate, tannate and acetate.

Preferably, the water-soluble rare earth salt comprises one or more of a nitrate, a sulfate, and a chloride of its corresponding rare earth element.

Preferably, the water-soluble molybdate, tungstate, silicate, titanate, nitrate, maleate, fumarate, borate, phytate, tartrate, citrate, acetate or tannate salt comprises at least one of its corresponding sodium, potassium, zinc, calcium and ammonium salts.

Preferably, the mass ratio of the reinforcing agent to the aluminum salt is 0.01 to 0.80; further preferably; preferably 0.1 to 0.3; more preferably 0.125 to 0.25.

The high-aluminum passivation solution consists of solvent water and the water-soluble aluminum salt. Or consists of solvent water, the water-soluble aluminum salt and acid. Or consists of solvent water, the water-soluble aluminum salt and an enhancer. Or consists of solvent water, the water-soluble aluminum salt, acid and an enhancer.

The temperature of the passivation process of the invention is, for example, 10 to 50 ℃; preferably 10 to 40 ℃.

In the process of intensive research, the inventor also finds that when the residual ammonium sulfate is solved, the high-concentration aluminum-based passivating agent is adopted, and if the temperature of a passivating system is effectively regulated, the maximum benefit of the ammonium sulfate can be exerted under the condition of no flushing, so that the efficient passivation of the electrolytic manganese is realized. In the temperature range of 10-50 ℃, the residual ammonium sulfate on the surface of the electrolytic manganese can play the greatest role in cooperation with a passivation system, and the construction of a compact passivation film layer is effectively promoted. The temperature is low (10 ℃), the ammonium sulfate reaction activity is low, the ammonium sulfate is difficult to effectively participate in the formation of the bimetallic hydrotalcite film layer, and partial ammonium sulfate residue is easy to cause further influence on the passivation effect; the temperature is higher (50 ℃), although ammonium sulfate can be accelerated to participate in the reaction to a certain degree, the self oxidation of the manganese metal can be accelerated, the divalent manganese ions on the surface interface are excessive, and the composition proportion and the crystal structure of the formed Mn-Al hydrotalcite film layer are further influenced. Thus, the properties of the formed film layer will also be affected to some extent.

Preferably, the passivation time is 20 seconds to 15 minutes; more preferably 1-8 min; more preferably 1 to 5min.

Advantageous effects

1. The invention discloses the problem of adverse effect of residual ammonium sulfate in the manganese electrolysis process in the Mn-Al passivation process for the first time, and provides a technical means for solving the problem of the ammonium sulfate influence and improving the passivation effect by adopting required high-concentration Al for the first time;

the low-concentration aluminum-based passivator has excellent passivation performance on electrolytic manganese under the condition of low ammonium sulfate concentration or cleaning firstly. However, if the concentration of ammonium sulfate is higher or more ammonium sulfate remains in the electrolytic manganese scale-up production process, the passivation performance of the electrolytic manganese is remarkably reduced. The present invention is therefore focused on solving the adverse effect of ammonium sulfate on the passivation process. The existence of ammonium sulfate can reduce the passivation effect of electrolytic manganese, so that the surface of the passivated electrolytic manganese part still turns yellow and black, and the corrosion resistance of a passivation film is obviously reduced. The passivating agent adopted by the invention is used for passivating the electrolytic manganese by using the high-concentration active component, so that the influence of ammonium sulfate on the passivation process can be effectively reduced, the surface of the passivated electrolytic manganese is hardly influenced, and the passivation performance of the high-concentration passivating agent is not influenced compared with that of the low-concentration passivating agent.

2. Under the condition of the aluminum salt passivation system with the required concentration, acid and/or a strengthening agent are further added, which is helpful for further improving the influence caused by ammonium sulfate and is helpful for further improving the passivation effect

For example, the acidic deactivator contains H ⁺ The active metal manganese acts on the surface of manganese with hydrogen ions to generate proper Mn ²⁺ Ions due to H ⁺ The local consumption of (b) causes the pH of the manganese metal surface to increase, resulting in Al in the passivating agent ³⁺ Fast reaction with Mn on the surface of metal manganese ²⁺ 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 passivator 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 cheaper and easily available in comparison with other metal inorganic salts, and is beneficial to reducing the cost, so that the passivator has a good industrial application prospect.

For another example, the enhancer is one or two of soluble rare earth salt, molybdate, tungstate, silicate, titanate, phosphate, maleate, fumarate, borate, phytate, tartrate, citrate, and tannate, and is used for further treatmentPromotion of Al ³⁺ With Mn ²⁺ Forming a hydrotalcite-like compound passivation film layer. Wherein the soluble trivalent rare earth salt can react with Al under acidic condition based on different atomic radii ³⁺ 、Mn ²⁺ 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, the soluble molybdate, tungstate, silicate, titanate, phosphate, maleate, fumarate, borate, phytate, tartrate, citrate and tannate used are mainly present in the form of acid anion in the solution, when Al is used ³⁺ 、Mn ²⁺ 、RE ³⁺ When the plasma forms the hydrotalcite-like film layer on the surface of the electrolytic manganese metal, based on the positive electricity characteristic of the hydrotalcite compound plate layer, anions are conveniently intercalated between the hydrotalcite compound plate layers, salt precipitation is 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.

Drawings

Fig. 1 is a Tafel plot of unpassivated manganese metal and passivated manganese metal prepared in example 15. 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 15.

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 15.

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 indicated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

In the following cases, the percentages are by weight unless otherwise stated.

(1) Study of Al concentration

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, the pH value of the catholyte is 6.8-7.0, and the current density is 400A/m ² Electrolyzing at 38 ℃ for 1.5h to obtain an electrolytic manganese product, wherein the prepared electrolytic manganese product is used for subsequent passivation experiments and passivation layer performance evaluation; detection shows that under the electrolysis condition, the residual quantity of ammonium sulfate in the unwashed electrolytic manganese is 2.03wt.%.

Preparing a passivating agent: 40g of aluminum sulfate was added to water to be dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH =2.0, to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (aluminum sulfate concentration of 4.0 wt.%).

Passivation and performance detection of electrolytic manganese products: and (3) placing the prepared chromium-free passivator in a passivation tank, then placing the cathode plate which is just taken out of the tank and is not cleaned in the passivation tank, immersing the surface of the cathode plate with the chromium-free passivator, passivating for 1.0 minute at normal temperature (20 ℃), 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 8.003 multiplied by 10 ^-7 A/cm ² 。

Comparative example 1:

compared with example 1, the difference is only the formulation of the passivating agent: 10g of aluminum sulfate was added to water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH =2.0, to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of aluminum sulfate was 1.0%, the residual amount of unwashed electrolytic manganese ammonium sulfate was the same as in example 1);

electrochemical performance of passivated manganese metal productsThe test shows that the self-corrosion current is 6.139 x 10 ^-5 A/cm ² 。

Comparative example 2:

compared with example 1, the only difference is the formulation of the passivating agent: 18g of aluminum sulfate was added to water and dissolved with stirring, and then hydrochloric acid was added to adjust the solution to pH =2.0, to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of aluminum sulfate was 1.8%, the residual amount of unwashed electrolytic manganese ammonium sulfate was the same as in example 1);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 2.708 multiplied by 10 ^-5 A/cm ² 。

Comparative example 3:

compared with example 1, the difference is only the formulation of the passivating agent: 15g of aluminum nitrate is added into water to be stirred and dissolved, and then sulfuric acid is added to adjust the pH of the solution to be =2.0, so that the chromium-free passivator for electrolytic manganese metal surface treatment is prepared (the mass concentration of the aluminum nitrate is 1.5%, and the residual quantity of the uncleaned electrolytic manganese ammonium sulfate is the same as that of example 1);

electrochemical performance test of passivated manganese metal product shows that the self-corrosion current is 1.441 multiplied by 10 ^-5 A/cm ² 。

Comparative example 4:

compared with example 1, the only difference is the formulation of the passivating agent: 500g of aluminum sulfate was added to water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH =2.0, to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of aluminum chloride was 50.0%, the residual amount of unwashed electrolytic manganese ammonium sulfate was the same as in example 1);

electrochemical performance test of passivated manganese metal product shows that the self-corrosion current is 1.269 multiplied by 10 ^-5 A/cm ² 。

Example 2:

compared with the example 1, the difference is only that different concentrations of aluminum sulfate are adopted (the mass concentrations are respectively 1%, 2%, 3%, 4%, 5%, 8%, 10%, 40% and 45%, and the residual quantity of the unwashed electrolytic manganese ammonium sulfate is the same as that of the example 1);

electrochemical tests are adopted to research the resistance of passivators with different concentrations to ammonium sulfate, and the electrochemical parameters are shown in table 1.

TABLE 1 comparison of ammonium sulfate tolerance for different deactivator concentrations

Test specimen	Self-corroding potential (V)	Self-corrosion current (A/m) ² )
			Unpassivated Mn	-1.379	3.782E ^-4
1％	-1.348	6.139E ^-5
			2％	-1.295	1.390E ^-6
3％	-1.284	4.527E ^-7
			4％	-1.277	8.003E ^-7
5％	-1.265	8.609E ^-7
			8％	-1.251	7.139E ^-7
10％	-1.260	9.121E ^-7
			40％	-1.272	9.872E ^-7
45％	-1.314	1.289E ^-6

As can be seen from the table 1, when the concentration of the passivator is low, the tolerance of the passivation process to ammonium sulfate is poor, and when the concentration of the ammonium sulfate is high, the passivated electrolytic manganese surface is partially yellow and black; the passivating agent with high concentration can obviously resist the adverse effect of ammonium sulfate, and the passivated electrolytic manganese surface presents silvery white and has good corrosion resistance; however, when the concentration reaches 45%, the passivation effect begins to decrease again, and the surface begins to turn yellow, possibly because too high a concentration of the passivation agent will make the acidity in the system too high to be beneficial for the construction of the passivation film layer.

(2) Cases simulating high concentrations of ammonium sulfate

Example 3:

the only difference compared to example 1 is that ammonium sulfate was artificially added to the passivation solution to simulate the effect of high concentrations of ammonium sulfate: 2g/L, 20g/L, 50g/L, 100g/L, 120g/L, 150g/L, 200g/L; the passivation performance was evaluated by using 4% and 15% aluminum sulfate, respectively (except for the concentration of the passivation agent, the passivation conditions were the same as in example 1).

The tolerance of 2 passivators to ammonium sulfate with different concentrations is researched by an electrochemical test, and the electrochemical parameters are shown in table 2.

TABLE 2 comparison of ammonium sulfate tolerance performance for passivating solutions of different concentrations

As can be seen from table 2, the high aluminum passivator has good resistance to high concentration of ammonium sulfate, but when the concentration of ammonium sulfate is too high, the resistance of the passivator is limited.

(3) Aluminum salt species study

Example 4:

compared with example 1, the difference is only that 40g of aluminum nitrate is used to replace equal mass of aluminum sulfate (the residual quantity of the electrolytic manganese ammonium sulfate which is not cleaned is the same as that of example 1);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 6.404 multiplied by 10 ^-7 A/cm ² 。

Example 5:

compared with example 1, the difference is only that 40g of aluminum chloride is used to replace equivalent mass of aluminum sulfate (the residual amount of ammonium sulfate is the same as that in example 1);

electrochemical performance test of passivated manganese metal product shows that the self-corrosion current is 5.115 multiplied by 10 ^-7 A/cm ² 。

Example 6:

compared with the example 1, the difference is only that 40g of aluminum citrate is used for replacing equal mass of aluminum sulfate (the residual quantity of the electrolytic manganese ammonium sulfate which is not cleaned is the same as that of the example 1);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 2.724 multiplied by 10 ^-7 A/cm ² 。

Comparative example 5:

compared with the example 1, the difference is only that 40g of aluminum sulfate is replaced by equal quality of ferric sulfate (the residual amount of the unwashed electrolytic manganese ammonium sulfate is the same as that of the example 1);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 1.845 multiplied by 10 ^-5 A/cm ² 。

Comparative example 6:

compared with the example 1, the difference is only that 40g of aluminum sulfate is replaced by cobalt chloride with equal mass (the residual quantity of the unwashed electrolytic ammonium manganese sulfate is the same as that in the example 1);

electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 1.234 multiplied by 10 ^-5 A/cm ² 。

From examples 4-6, it can be seen that high concentrations of different aluminum salts all have resistance to ammonium sulfate, while aluminum citrate exhibits better resistance, probably because citrate ions act synergistically with aluminum ions in the passivation solution to form a film on the surface of electrolytic manganese, thereby exhibiting better corrosion resistance and thus ammonium sulfate resistance. Further, it is understood from example 1 and comparative examples 5 and 6 that, although the hydrotalcite structure can be formed by the aluminum, iron, cobalt, etc., only Al is present ³⁺ Shows better passivation effect and ammonium sulfate tolerance, which is probably similar to Al ³⁺ The nature of which is related to the ionic radius.

(4) Acid addition study;

example 7:

compared with the example 1, the difference is only that the pH of the passivation solution is adjusted by nitric acid (the residual quantity of the unwashed electrolytic manganese ammonium sulfate is the same as that of the example 1);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 6.079 multiplied by 10 ^-7 A/cm ² 。

Example 8:

compared with the example 1, the difference is only that the pH value of the passivation solution is adjusted by using acetic acid (the residual quantity of the unwashed electrolytic manganese ammonium sulfate is the same as that of the example 1);

for passivated manganese metalThe electrochemical performance test of the product shows that the self-corrosion current is 2.112 multiplied by 10 ^-7 A/cm ² 。

Example 9:

compared with the example 1, the difference is that the passivation solution is not subjected to acidity regulation and control, and after the preparation is completed, the pH value of the passivation solution is 4.6 (the residual quantity of the unwashed electrolytic manganese ammonium sulfate is the same as that of the example 1);

electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 1.634 multiplied by 10 ^-6 A/cm ² 。

(5) Research of a reinforcing agent;

example 10:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate and 5g of cerium nitrate were added to water and dissolved with stirring to obtain a chromium-free passivator for electrolytic manganese metal surface treatment (aluminum salt mass concentration 4%, cerium nitrate concentration 0.5%, residual amount of unwashed electrolytic manganese ammonium sulfate same as example 1).

Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 6.336 multiplied by 10 ^-7 A/cm ² 。

Comparative example 7:

compared with example 1, the difference is only the formulation of the passivating agent: 10g of aluminum sulfate and 5g of cerium nitrate are added into water and stirred to be dissolved, so as to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of aluminum salt is 1.0%, the concentration of cerium nitrate is 0.5%, and the residual amount of uncleaned electrolytic manganese ammonium sulfate is the same as that in example 1);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 1.208 multiplied by 10 ^-5 A/cm ² 。

Example 11:

compared with example 1, the only difference is the formulation of the passivating agent: 40g of aluminum sulfate and 5g of sodium molybdate were added to water and dissolved with stirring to obtain a chromium-free passivator for electrolytic manganese metal surface treatment (mass concentration of aluminum salt: 4%, residual amount of unwashed electrolytic manganese ammonium sulfate in the same manner as in example 1).

Electrochemical performance test of passivated manganese metal product shows that the self-corrosion current is 5.727 multiplied by 10 ^-7 A/cm ² 。

Example 12:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate, 5g of cerium nitrate and 5g of sodium molybdate were added to water and stirred to dissolve, thereby obtaining a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of aluminum salt is 4%, and the residual amount of unwashed electrolytic manganese ammonium sulfate is the same as in example 1).

Electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 2.416 multiplied by 10 ^-7 A/cm ² 。

Electrochemical tests are adopted to research the strengthening effect of different reinforcing agents in the passivating agent, and the electrochemical parameters are shown in table 3.

TABLE 3 strengthening Effect of the enhancers

Test specimen	Self-corroding potential (V)	Self-corrosion current (A/m) ² )
			Non-passivated Mn	-1.379	3.782E ^-4
Example 1	-1.277	8.003E ^-7
			Example 10	-1.307	6.336E ^-7
Comparative example 7	-1.315	1.208E ^-5
			Example 11	-1.312	5.727E ^-7
Example 12	-1.297	2.416E ^-7

As can be seen from Table 3, the passivation effect of the passivator can be further improved by adding the reinforcing agent, and the influence of ammonium sulfate can be synergistically resisted. Introduction of soluble RE ³⁺ Based on the difference in atomic radius, can react with Al under acidic conditions ³⁺ 、Mn ²⁺ The hydrotalcite-like compound passivation film layer is formed cooperatively, so that the passivation film layer is more compact, and the passivation performance is more excellent; acid radical anions are introduced, and the hydrotalcite compound plate layers are positively charged, so that the hydrotalcite compound plate layers are conveniently intercalated between the hydrotalcite plate layers, and salt precipitation is 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 are improved. When RE is introduced at the same time ³⁺ And acid radical anions, the two can generate a synergistic effect, the passivation performance of the electrolytic manganese surface is obviously improved, and the ammonium sulfate has good tolerance performance.

(6) Acid addition plus fortifier study;

example 13:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate and 5g of cerium nitrate were added to water and dissolved with stirring, followed by addition of sulfuric acid to adjust the solution to pH =2.0, to obtain a chromium-free passivator for electrolytic manganese metal surface treatment (mass concentration of aluminum salt 4%, residual amount of unwashed electrolytic manganese ammonium sulfate the same as in example 1).

Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 4.081 multiplied by 10 ^-7 A/cm ² 。

Example 14:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate and 5g of sodium molybdate were added to 1L of water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH =2.0, to obtain a chromium-free passivating agent for electrolytic manganese metal surface treatment (the mass concentration of aluminum salt was 4%, and the residual amount of uncleaned electrolytic manganese ammonium sulfate was the same as in example 1).

Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 4.332 multiplied by 10 ^-7 A/cm ² 。

Example 15:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate, 5g of cerium nitrate and 5g of sodium molybdate were added to 1L of water and dissolved with stirring, and then sulfuric acid was added to adjust the solution to pH =2.0, to obtain a chromium-free passivation agent for electrolytic manganese metal surface treatment (the mass concentration of aluminum salt was 4%, and the amount of residual ammonium sulfate of electrolytic manganese not cleaned was the same as in example 1).

Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 7.881 multiplied by 10 ^-8 A/cm ² 。

Example 16:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate, 5g of cerium nitrate and 5g of sodium molybdate were added to 1L of water and dissolved with stirring, followed by addition of nitric acid to adjust the solution to pH =2.0, to obtain a chromium-free passivator for electrolytic manganese metal surface treatment (mass concentration of aluminum salt: 4%, residual amount of unwashed electrolytic manganese ammonium sulfate as in example 1).

Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 1.069 multiplied by 10 ^-7 A/cm ² 。

Example 17:

compared with example 1, the difference is only the formulation of the passivating agent: 40g of aluminum sulfate, 5g of cerium nitrate and 5g of sodium molybdate were added to 1L of water and dissolved with stirring, followed by addition of acetic acid to adjust the solution to pH =2.0, to obtain a chromium-free passivator for electrolytic manganese metal surface treatment (mass concentration of aluminum salt: 4%, residual amount of unwashed electrolytic manganese ammonium sulfate as in example 1).

Electrochemical performance test of passivated manganese metal product shows that the self-corrosion current is 2.051 multiplied by 10 ^-7 A/cm ² 。

The strengthening effect of the acid and the strengthening agent in the passivating agent is researched by adopting an electrochemical test, and the electrochemical parameters are shown in table 4.

TABLE 4 fortification Effect of acid + fortifier

Test specimen	Self-corroding potential (V)	Self-corrosion current (A/m) ² )
			Non-passivated Mn	-1.379	3.782E ^-4
Example 1	-1.277	8.003E ^-7
			Example 13	-1.333	4.081E ^-7
Example 14	-1.286	4.332E ^-7
			Example 15	-1.238	7.881E ^-8
Example 16	-1.284	1.069E ^-7
			Example 17	-1.298	2.051E ^-7

As can be seen from Table 4, the simultaneous addition of acid and reinforcing agent further enhances the passivation effect and also further enhances the ammonium sulfate tolerance. This may be due to H ⁺ Increase of (2) promotes Mn ²⁺ The generation of ions further accelerates Al in the passivating agent ³⁺ Mn with surface of metal manganese ²⁺ Crystallizing to form a hydrotalcite-like compound passivation film layer. And the film formation is promoted, so that the passivation effect of the passivator is further improved. After the electrolytic manganese product is passivated, the self-corrosion potential of the product is obviously shifted positively, the self-corrosion potential is shifted positively by 141mV, the corresponding self-corrosion current is reduced by 4 orders of magnitude, and the corrosion resistance of the electrolytic manganese 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 electrolytic manganese which has just been electrolyzed and has not been passivated has a plurality of hairy flaky oxides on the surface, and the surface is obviously oxidized. In fig. 3, it can be seen that the surface of the passivated manganese metal product is obviously smooth and flat, and is hardly oxidized.

(8) Influence of passivation temperature and passivation time

Example 18:

compared with example 1, the only difference is that the passivation temperatures are set to: the same procedure as in example 1 was repeated except that the electrolytic manganese ammonium sulfate was not washed at 8 ℃,10 ℃, 20 ℃, 30 ℃, 35 ℃, 40 ℃, 50 ℃ and 60 ℃;

the electrochemical test is adopted to research the resistance of the passivator to ammonium sulfate with different concentrations, and the electrochemical parameters are shown in table 5.

TABLE 5 influence of passivation temperature

Test specimen	Self-corroding potential (V)	Self-corrosion current (A/m) ² )
			Unpassivated Mn	-1.379	3.782E ^-4
8℃	-1.331	5.732E ^-6
			10℃	-1.284	8.732E ^-7
20℃	-1.277	8.003E ^-7
			30℃	-1.297	9.610E ^-7
35℃	-1.301	8.024E ^-7
			40℃	-1.294	9.925E ^-7
50℃	-1.309	1.622E ^-6
			60℃	-1.327	2.024E ^-5

As can be seen from Table 5, the passivation temperature has a significant effect on the corrosion resistance and ammonium sulfate tolerance of the high-aluminum passivator, and the passivation performance is better within the range of 10-40 ℃.

Example 19:

compared with example 1, the only difference is that the passivation times are set as: 20s, 1min, 2min, 5min, 10min, 15min and 20min (the residual quantity of the unwashed electrolytic manganese ammonium sulfate is the same as that of the embodiment 1);

the electrochemical test is adopted to research the resistance of the passivator to ammonium sulfate with different concentrations, and the electrochemical parameters are shown in table 6.

TABLE 6 influence of passivation time

As can be seen from Table 6, the passivation time has little influence on the corrosion resistance and ammonium sulfate resistance of the high-aluminum passivator, but the passivation time is too long and is also unfavorable, and an optimized interval exists in the passivation time. When the passivation time is as long as 20 minutes, the passivation effect is significantly reduced, which may be due to the fact that the passivation film layer is too thick and exhibits a loose and porous structure, thereby reducing the corrosion resistance of the film layer.

Example 20:

the production conditions of the electrolytic manganese metal product were the same as in example 1. The passivator used in the embodiment 20 is an aluminum-based chromium-free passivator (the concentration of the aluminum-based passivator is 4 percent in the same way as that in the embodiment 1), the pH value of the passivating solution is 3.0-3.5, and the passivating time is 2.0min. Electrolytic manganese is continuously produced, and the acid consumption in the passivation process is monitored. Tests show that after the electrolytic manganese is produced out of the tank (the residual quantity of the ammonium sulfate of the electrolytic manganese which is not cleaned is 2.17 wt.%), an aluminum-based chromium-free passivation solution is directly adopted for passivation for 2.0min, and the electrolytic manganese is taken out and placed in an aeration tank for treatment for 10min and dried to obtain a passivated manganese metal product. The technical scheme is that the acid consumption for passivation is 0.25Kg 98 percent H for each 1 ton of electrolytic manganese production ₂ SO ₄ . Mn content of electrolytic manganese product>99.9 percent and 0.013 percent of S. Electrochemical performance tests are carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 5.947 multiplied by 10 ^-7 A/cm ² 。

Comparative example 8:

compared with the embodiment 20, the difference is that 1.0 percent of aluminum-based chromium-free passivating agent is adopted to verify the passivating effect and the acid consumption condition, and the method specifically comprises the following steps:

the production conditions of the electrolytic manganese metal product were the same as in example 1. The passivating agent used in the comparative example 1 is 1.0 percent of aluminum-based chromium-free passivating agent, the pH value of the passivating solution is 3.0-3.5, and the passivating time is 2.0min. Electrolytic manganese is continuously produced, and the acid consumption in the passivation process is monitored. The test shows that after the electrolytic manganese is produced out of the tank (the residual ammonium sulfate of the electrolytic manganese is not cleaned)The residual amount is 2.17 wt.%), aluminium-based chromium-free passivation solution is directly adopted for passivation for 2.0min, and the aluminium-based chromium-free passivation solution is taken out and placed in an aeration tank for treatment for 10min and dried to obtain a passivated manganese metal product. The technical proposal has the acid consumption of passivation of 0.29Kg 98 percent H for producing 1 ton of electrolytic manganese ₂ SO ₄ . Mn content of electrolytic manganese product>99.9 percent and 0.017 percent of S. Electrochemical performance test of passivated manganese metal product shows that the self-corrosion current is 1.127 multiplied by 10 ^-5 A/cm ² 。

Comparative example 9:

compared with the embodiment 20, the difference is that 1.0% of aluminum-based chromium-free passivator is adopted, ammonium sulfate is removed by carefully washing before passivation, and the passivation effect and the acid consumption condition are verified, specifically:

the production conditions of the electrolytic manganese metal product were the same as in example 1. The passivator used in the comparative example 2 is 1.0 percent of aluminum-based chromium-free passivator, the pH of the passivating solution is 3.0-3.5, and the passivating time is 2.0min. Electrolytic manganese is continuously produced, and the acid consumption in the passivation process is monitored. Tests show that after electrolytic manganese is produced out of a tank, the electrolytic manganese is washed by clear water (the residual amount of ammonium sulfate is 0.03%), then passivated by aluminum-based chromium-free passivation solution for 2.0min, taken out and dried to obtain a passivated manganese metal product. According to the technical scheme, the acid consumption for passivation is 1.37Kg 98 percent H for each 1 ton of electrolytic manganese ₂ SO ₄ . Mn content of electrolytic manganese product>99.9 percent and the S content is 0.021 percent. Electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 5.197 multiplied by 10 ^-7 A/cm ² 。

Compared with the comparative example, the method of the invention can effectively reduce the acid consumption of continuous production while ensuring the passivation performance.

The conclusion shows that the high-concentration aluminum-based passivator can keep the surface of the electrolytic manganese which is just taken out of the tank and not cleaned to show silvery white metallic luster required by practical application, and meanwhile, the surface also has good corrosion resistance. This shows that the high concentration aluminum salt passivator not only has good ammonium sulfate tolerance, but also has good passivation effect. While low concentrations of aluminum salts do not resist the adverse effects of residual ammonium sulfate, and the passivated surface tends to yellow and black due to the presence of ammonium sulfate. The high-concentration aluminum salt passivator adopted by the invention simultaneously meets the corrosion resistance and ammonium sulfate tolerance of passivation, and has important practical application value for solving the influence of residual ammonium sulfate in electrolytic manganese industry.

Example 21:

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: 100g/L of ammonium sulfate, 76.9g/L of manganese sulfate and 0.05g/L of selenium dioxide, the pH value of the catholyte is 6.8-7.0, and the current density is 400A/m ² The electrolytic temperature is 38 ℃, the electrolytic time is 1.5h, and the electrolytic manganese product is prepared and used for subsequent passivation experiments and passivation layer performance evaluation; detection shows that under the electrolysis condition, the residual quantity of ammonium sulfate in the unwashed electrolytic manganese is 1.82wt.%.

Compared with the embodiment 1, the difference is that the concentration of the ammonium sulfate adopted in the electrolytic manganese preparation process is 100g/L; preparing a passivating agent: adding 60g of aluminum sulfate into water, stirring and dissolving, and then adding sulfuric acid to adjust the pH of the solution to be =3.0, so as to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of the aluminum sulfate is 6.0%, and the residual quantity of unwashed electrolytic manganese ammonium sulfate is 1.82 wt%);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 6.281 multiplied by 10 ^-7 A/cm ² 。

Example 22:

compared with the example 1, the difference is only that in the electrolytic manganese preparation process, the concentration of the adopted ammonium sulfate is 140g/L, and the residual quantity of the prepared unwashed electrolytic manganese ammonium sulfate is 2.23wt.%; preparing a passivating agent: adding 300g of aluminum sulfate into water, stirring and dissolving, and then adding hydrochloric acid to adjust the pH of the solution to be =4.0, so as to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of the aluminum sulfate is 30.0%);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 7.043 multiplied by 10 ^-7 A/cm ² 。

Example 23:

compared with the example 1, the difference is only that the concentration of the adopted ammonium sulfate in the electrolytic manganese preparation process is 80g/L, and the residual quantity of the unwashed electrolytic manganese ammonium sulfate is 1.47wt.%; preparing a passivating agent: adding 50g of aluminum sulfate into water, stirring and dissolving, and then adding hydrochloric acid to adjust the pH of the solution to be 3.0, so as to prepare a chromium-free passivator for electrolytic manganese metal surface treatment (the mass concentration of the aluminum sulfate is 5.0%);

electrochemical performance test is carried out on the passivated manganese metal product, and the result shows that the self-corrosion current is 5.316 multiplied by 10 ^-7 A/cm ² 。

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.

Because the electrolyte of the electrolytic manganese contains a large amount of ammonium sulfate, the ammonium sulfate is easy to crystallize and precipitate on the upper layer boundary of the electrolytic manganese after long-term electrolysis, so that the electrolytic manganese is brought into the next passivation process. And the existence of the residual ammonium sulfate is easy to reduce the passivation effect, so that the surface of the passivated electrolytic manganese still turns yellow and black, and the use value of the passivated electrolytic manganese is reduced. The invention adopts the high-concentration aluminum salt passivator, can effectively resist the adverse effect brought by ammonium sulfate in the passivation process, so that the electrolytic manganese surface keeps the original silvery white metallic luster, and has good surface tolerance. Meanwhile, the high-concentration passivator can reduce the adding times of the later passivator make-up fluid, save the operation cost, simplify the process flow and have important practical application value.

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 acid system with pH = 1.0-5.5, and Al element is Al under the acid condition ³⁺ The form exists. Active metal manganese and H ⁺ Act on the surface to generate a proper amount of Mn ²⁺ ，Mn ²⁺ Under the environment that the pH of the surface of the metal manganese is locally increased, the metal manganese is easy to react with Al ³⁺ 、RE ³⁺ 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.

The reinforcing agent used in the chromium-free passivation solution is soluble trivalent rare earth ions or soluble acid radical anions, and can further improve the compactness of a passivation film layer and improve the passivation effect on the basis of forming a hydrotalcite-like passivation film by aluminum salt.

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 and the promotion effect of adding acid. Compared with the self-corrosion potential of the manganese metal product before passivation, the self-corrosion potential after passivation is shifted by 141mV, and the corresponding self-corrosion current is reduced by 4 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. All possible combinations of the technical features of the above embodiments may not be described for the sake of brevity, but should be considered as within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.

Claims

1. The chromium-free passivation method of electrolytic manganese is characterized in that electrolytic manganese obtained by electrolysis is directly placed in a high-aluminum passivation solution for passivation without being cleaned;

the high-aluminum passivation solution is an aluminum salt homogeneous phase aqueous solution; wherein the mass percent concentration of the aluminum salt is greater than 2.0wt.%.

2. The method for chromium-free passivation of electrolytic manganese according to claim 1, wherein the electrolytic manganese is electrolytic manganese with residual ammonium sulfate;

3. The method of claim 2, wherein the electrolytic manganese is obtained by electrolysis in an electrolyte comprising ammonium sulfate and manganese sulfate.

4. The method for chromium-free passivation of electrolytic manganese according to claim 1, wherein said aluminum salt is one or more of aluminum citrate, aluminum acetate, aluminum sulfate, aluminum chloride, aluminum nitrate, polyaluminum chloride, polyaluminum sulfate.

5. The chromium-free passivation method of electrolytic manganese of claim 1, wherein in the high-aluminum passivation solution, the mass percentage concentration of aluminum salt is 2.5-45.0%; more preferably from 3.0 to 5.0wt.% or from 10.0 to 40.0wt.%.

6. The chromium-free passivation method of electrolytic manganese according to any one of claims 1 to 5, wherein said high aluminum passivation solution further comprises an acid;

preferably, the acid is one or more of nitric acid, sulfuric acid, hydrochloric acid, acetic acid and citric acid.

7. The chromium-free passivation method of electrolytic manganese according to claim 6, wherein the high aluminum passivation solution has a pH of 1.0 to 5.5; more preferably 2.0 to 4.5.

8. The chromium-free passivation method of electrolytic manganese according to any one of claims 1 to 7, wherein a strengthening agent is further added to the high aluminum passivation solution;

the reinforcing agent is rare earth salt (RE) ³⁺ 、RE ⁴⁺ ) At least one water-soluble salt selected from the group consisting of molybdate, tungstate, silicate, titanate, nitrate, maleate, fumarate, borate, phytate, tartrate, citrate, tannate and acetate;

preferably, the water-soluble rare earth salt comprises one or more of its corresponding nitrate, sulphate and chloride.

Preferably, the water soluble molybdate, tungstate, silicate, titanate, nitrate, maleate, fumarate, borate, phytate, tartrate, citrate, acetate or tannate salt comprises at least one of its corresponding sodium, potassium, zinc, calcium and ammonium salts.

9. The method of chromium-free passivation of electrolytic manganese according to claim 8, characterized in that the mass ratio of said reinforcing agent to said aluminum salt is preferably 0.01 to 0.80; preferably 0.1 to 0.3; more preferably 0.125 to 0.25.

10. The chromium-free passivation method of electrolytic manganese of claim 1, wherein the temperature of the passivation process is 10-50 ℃; preferably 10 to 40 ℃;