CN116288303A

CN116288303A - Cobalt-free passivation solution for zinc and zinc alloy surface deposition and preparation method thereof

Info

Publication number: CN116288303A
Application number: CN202310059136.9A
Authority: CN
Inventors: 潘文亮
Original assignee: Foshan Nanhai Gaoyimei Environmental Protection Industry Co ltd
Current assignee: Foshan Nanhai Gaoyimei Environmental Protection Industry Co ltd
Priority date: 2023-01-18
Filing date: 2023-01-18
Publication date: 2023-06-23

Abstract

The invention discloses a zinc and zinc alloy surface deposition cobalt-free passivation solution and a preparation method thereof, wherein the zinc and zinc alloy surface deposition cobalt-free passivation solution comprises chromium compounds of Cr < 3+ > 258-35g/L, complexing agents of 40-70g/L, organic acids of 50-90g/L, inorganic acids of 20-70g/L, inorganic salts of 65-102g/L and water. The complexing agent is sodium fluoride or ammonium fluoborate. The chromium compound is one or more than two of chromium nitrate, potassium chromium sulfate or chromium chloride. Does not contain cobalt compounds. The inorganic salt is one or more than two of sodium sulfate, vanadyl sulfate or zirconium sulfate. The organic acid is one or more than two of oxalic acid dihydrate, tartaric acid, malonic acid, citric acid, glacial acetic acid, lactic acid or amino acetic acid. The passivation film obtained by matching a proper amount of reducing agent in the passivation solution with a proper amount of organic acid, chromium compound and vanadium or zirconium compound has good corrosion resistance and is not easy to oxidize into hexavalent chromium; the surface of the passivation layer is smooth, beautiful and has no micropores.

Description

Cobalt-free passivation solution for zinc and zinc alloy surface deposition and preparation method thereof

Technical Field

The invention relates to a cobalt-free passivation solution for zinc and zinc alloy surface deposition and a preparation method thereof, belonging to the technical field of metal surface treatment.

Background

In order to improve corrosion resistance of steel products, a galvanized layer is usually formed on the surface of the product by plating zinc or alloys thereof (zinc nickel, zinc diamond and zinc iron), and in order to further improve corrosion resistance and decoration, the galvanized layer must be subjected to passivation treatment to form a passivation film with high corrosion resistance and good decoration. In the past, hexavalent chromium is always adopted for passivation treatment, the hexavalent chromium passivation process is mature and stable, the corrosion resistance is high, the self-healing capacity of repairing the corrosion resistance is realized, the raw material sources are wide and the cost is low, but the hexavalent chromium has high toxicity and carcinogenicity, and serious adverse effects on the environment and the human health exist, so that the zinc coating adopts the trivalent chromium passivation process to replace the hexavalent chromium passivation process, and the technical problem which must be solved in the surface treatment industry is solved.

However, protection against corrosion is to be achieved, since it is necessary, for example, in the standard DIN50979, which is known in the art, such additional passivation being based on trivalent chromium compounds and may also contain water-soluble cobalt compounds, for example in the form of cobalt sulfate or cobalt nitrate. These cobalt compounds are classified according to the label 1272/2008/EC for substances suspected of causing human cancers. Thus, there is an urgent need for cobalt-free passivation, according to DIN50979, in which at least the corrosion resistance requirements are met.

The related trivalent chromium color passivating agent reported at home and abroad generally comprises trivalent chromium salt (main film forming agent), cobalt salt (auxiliary film forming agent), fluoride ion (complexing agent), sulfuric acid (film forming accelerator), nitric acid (film forming accelerator) and other components. In order to improve the corrosion resistance, phosphates, silicates, rare earth metal salts, and the like may also be added. The invention patent USP 6287704 proposes a high-concentration passivating agent formula of 50g/L chromium chloride, 100g/L sodium nitrate, 3g/L cobalt nitrate and 31.2g/L malonic acid, and an iridescent passivating film with the thickness of 100-1000nm can be obtained at the temperature of 50-70 ℃ and has extremely excellent corrosion resistance. However, the high-concentration passivation solution has high production cost, and the loss brought by the workpiece is extremely large, so that the passivation solution is difficult for a user to bear. Meanwhile, the operation is carried out at a higher temperature of 50-70 ℃, so that the energy consumption is high, the working environment is bad, and the environment is not protected.

The metallic galvanized layer passivated by the existing trivalent chromium color passivating agent technology can obtain corrosion resistance and brightness to a certain extent, but the corrosion resistance is still quite different from the requirement of the current industries such as automobiles, electronics and the like on the high corrosion resistance of galvanized workpieces. This is mainly related to the rough surface of the passivation layer formed by the existing passivation solution and the existence of a plurality of micro-hole defects, and the rough surface and the micro-hole defects affect the brightness of the passivation layer and the corrosion resistance of the passivation layer. The complexing agent in the prior art is added into the passivation solution or the passivation layer is subjected to sealing treatment by adopting a sealing agent after passivation, so that the appearance of the passivation layer is seriously influenced although the corrosion resistance of the passivation layer can be improved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a cobalt-free passivation solution for zinc and zinc alloy surface deposition. The passivation film obtained by using a proper amount of reducing agent in the passivation solution and a proper amount of organic acid, chromium compound and vanadium or zirconium compound in a matching way has good corrosion resistance and is not easy to be oxidized into hexavalent chromium.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a zinc and zinc alloy surface deposited cobalt-free passivation solution comprising: cr < 3+ > compound containing 2-4g/L of chromium, 5-15g/L of organic acid, vanadium compound containing 1.2-5g/L of vanadium, zirconium compound containing 1-2g/L of zirconium, 2-4g/L of complexing agent, 1-3g/L of NaOH,10-30g/L of N03-,0.5-10g/L of inorganic acid and the balance of pure water.

The complexing agent is one or more than two of ammonium fluoborate or sodium fluoride.

The chromium compound (Cr3+ compound) is one or more than two of chromium nitrate, potassium chromium sulfate or chromium chloride.

The vanadium compound is one or more than two of vanadyl sulfate, vanadic anhydride or vanadic oxalate.

The zirconium compound is one or more than two of zirconium nitrate and zirconium sulfate.

The complexing agent is one or more than two of dicyandiamide, HEDP or NTA.

The organic acid is one or more than two of oxalic acid dihydrate, tartaric acid, malonic acid, citric acid, glacial acetic acid, lactic acid or amino acetic acid.

The inorganic acid is sulfuric acid or nitric acid.

The zinc and zinc alloy surface deposition cobalt-free passivation solution is characterized in that a trivalent chromium chemical conversion film is formed on the surface of zinc plating or zinc plating alloy, the corrosion resistance (white rust occurrence time) of the trivalent chemical conversion film in a salt water spray test is more than 200 hours, the hexavalent chromium concentration in terms of metal atoms in the chemical conversion film is less than 0.0l mug/cm < 2 >, and the leaching amount of hexavalent chromium (leaching amount when the film is immersed in hot water at 100 ℃ for 10 minutes) after being placed in a constant temperature and humidity tank at 80 ℃ and humidity of 95% for 60 days is less than 0.05 mug/cm < 2 >.

Compared with the prior art, the invention has the advantages that:

(1) The cobalt-free passivation solution is deposited on the surfaces of zinc and zinc alloy, so that the corrosion resistance of a passivation product can be greatly improved, and the corrosion resistance exceeds 200 hours as measured by a 5% NaCI neutral salt spray test (NSS) of GB/T10125-1997, so that the requirements of most high corrosion resistance industrial products can be met, and meanwhile, the preparation of the passivation agent and the passivation process are simple and convenient to operate, and the passivation cost is low.

(2) The cobalt-free passivation solution deposited on the surfaces of the zinc and the zinc alloy does not contain hexavalent chromium, and the production process has no hexavalent chromium pollution, so that the production cost is low, and the method is economical and practical; the high corrosion-resistant trivalent chromium color passivating agent is completely free of hexavalent chromium, and is an environment-friendly low-concentration galvanized layer passivating agent; by adding vanadate, an iridescent passivation film can be formed on the galvanized layer at normal temperature. In the passivation process, vanadium ions in the solution can be deposited in the passivation film, so that the corrosion resistance of the passivation film is remarkably improved. The organic carboxylic acid can promote the growth of the passivation film and is beneficial to improving the thickness of the passivation film. In addition, it is an essential passivation of vanadium in cationic form, i.e. the invention as vanadyl cation has examples of vanadium compounds in cationic form, which demonstrate that passivation can use both VCl 3 and VBR 3, vanadyl sulfate (VOSO 4), vanadium acetylacetonate (V (acetylacetonate can also be prepared, for example, from vanadyl sulfate first reacted with 5 moles of sodium acetate; preferably in the present invention, passivation of vanadyl sulfate and/or vanadyl diacetylamino complex comprises; in the case of vanadyl sulfate and vanadyl diacetylamino complex, it is in the oxidation state +4 vanadium, and the compound has covalent v=o bonds; the Cr/V achieved when the corrosion resistance is optimal is in a weight ratio of 5/1 to 100/1, particularly preferably Cr/V from 10/1 to 50/1.

(3) Trivalent chromium coatings are prepared on zinc-iron alloys by electroless plating, and when the replacement fluid changes chelating additives, such as: sodium hydroxide, tartaric acid, several conclusions were drawn from the analysis of magnetic turbo film thickness, X-ray energy dispersive analyzer (EDS), vickers hardness tester, scanning Electron Microscope (SEM), X-ray diffraction instrument, tafel electrochemical test: the addition of 0.25M, 0.5M, 0.75M, 1M and 1.25M sodium hydroxide causes the phenomenon of sudden boiling of temperature due to the addition of sodium hydroxide to the chelating solution, and forms crystalline hydroxide with chromium potassium sulfate and oxalic acid, which results in poor surface flatness, so that the addition of 0.5M sodium hydroxide chelate has the best corrosion resistance effect, and the analysis results by various instruments show that the analysis trend graph of the oxide film thickness has the maximum value of 1.55 μm at 0.5M. As for the addition of 0.25M, 0.5M, 0.75M, 1M, and 1.25M tartaric acid in the 0.25M tartaric acid chelate addition has the best corrosion resistance, and as is known from the Tafel electrochemical test results, although the range of the passivation region is wide without adding sodium hydroxide, no hydroxide having poor corrosion resistance is formed on the surface of the substitution layer, and therefore, experiments with the addition of sodium hydroxide + tartaric acid have found that the addition of two complexing agents does not have an additive effect on corrosion resistance, but rather, the addition efficiency of sodium hydroxide is reduced, but if the use of a chelate solution with sodium hydroxide is used for a long time, the use of the chelate solution with sodium hydroxide is not recommended because the addition of sodium hydroxide will deteriorate the stability of the plating bath. The Tafel results above were shown to be: the addition of 0.5M sodium hydroxide > 0.25M tartaric acid +0.5M sodium hydroxide, on the contrary, results in poor substitution rate and thus poor corrosion resistance.

(4) The substitution layer treated with trivalent chromium solution added with 0.01M, 0.02M, 0.03M, 0.04M, 0.05M sodium fluoride solution was placed in 5wt% sodium chloride solution and subjected to scanning potential ranging from-2V to 1V using electrochemical instrument analysis and scanning rate 2mV/s, thereby observing corrosion resistance comparison of the trivalent chromium substitution layer. The passivation region range is wider in 0.01M sodium fluoride, the passivation region with lower corrosion potential is opened at-0.2V, and the open loop potential tends to rise more and more with the increase of the concentration of sodium fluoride. As is clear from the taver results, as the concentration of sodium fluoride increases, the passivation area behind the open loop potential is found to have a tendency to gradually decrease in extent because the zinc coating is dissolved during the formation of the chromium oxide film; thus, too high a concentration of fluoride ions causes an increase in the roughness of the surface of the substitution layer, and the substitution rate is poor, so that the surface of the substitution layer of trivalent chromium may exhibit a poor corrosion resistance that indicates a poor substitution layer.

(5) In the experiment, 0.01M, 0.02M, 0.03M, 0.04M and 0.05M ammonium tetrafluoroborate are added into passivation solution, the ring-opening potential of the ammonium tetrafluoroborate is gradually increased from 0.01M to 0.03M, and the passivation area range is reduced along with the increase of the concentration of the ammonium fluoroborate. However, 0.04M ammonium fluoborate has the lowest open loop potential of-1.18V and corrosion current value of 0.69A/cm < 2 >, although no passivation area is generated, the five concentrations directly tend to be stable after being analyzed by Taver, and the lowest corrosion potential of 0.301A/cm < 2 >, because fluoride ions attack the surface of a galvanized layer and borate of ammonium fluoborate has an inhibition effect, ammonium ions are stable metals, can improve the corrosion resistance and increase the replacement rate of a plating layer, and therefore when the adhesiveness of deposited metal oxide is good, the deposition rate and compactness of an oxide film can be increased to greatly improve the corrosion resistance. In the case where the concentration of ammonium fluoroborate is increased to 0.05M, the open loop potential is relatively close to the positive potential, but the corrosion current rises, and the passivation region is directly stabilized without being generated.

The cobalt-free passivation solution is deposited on the surfaces of zinc and zinc alloy, and an iridescent passivation film with good corrosion resistance can be generated on the surface of a galvanized layer at room temperature, so that the method is beneficial to environmental protection and simultaneously saves energy consumption.

The invention has the beneficial effects that:

the cobalt-free passivation solution deposited on the surfaces of zinc and zinc alloy not only improves the corrosion resistance of the zinc plating, but also combines the excellent corrosion resistance of the special trivalent chromium chemical conversion film. Further, a film obtained by directly forming a trivalent chromium conversion coating on zinc plating does not substantially cause elution of hexavalent chromium by leaving the film, has corrosion resistance and brine resistance equal to or higher than those of conventional hexavalent chromates, and can be used in various hues. In addition, the zinc and zinc alloy surface deposition cobalt-free passivation solution of the present invention capable of forming such a chemical conversion film is advantageous for wastewater treatment and economically advantageous because the trivalent chromium concentration in the treatment solution is low and the organic acid concentration and nitrogen concentration are also reduced.

Detailed Description

The following describes the invention in more detail. The description of these embodiments is provided to assist understanding of the present invention, but is not intended to limit the present invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

Inventive example 1:

a preparation method of a cobalt-free passivation solution for zinc and zinc alloy surface deposition comprises the following steps:

adding 500g of pure water, heating to 80 ℃, continuously stirring, dissolving 23g of chromium nitrate (nine water) containing chromium in the pure water, adding 3g of tartaric acid, stirring and dissolving, preserving heat for 30 minutes at 80 ℃, then adding 10-15g of 20% concentration sodium hydroxide solution, adjusting the PH to 2.4-2.6, sequentially adding 0.42g of sodium fluoride and 5.6g of ammonium fluoborate, preserving heat for 2 hours at 80 ℃, cooling to 60 ℃, adding 0.65g of vanadyl sulfate, adding 0.6g of 98% sulfuric acid after the raw materials are completely dissolved, fully reacting for 0.5 hours, cooling to 60 ℃, adding 0.9g of NTA, preserving heat for 1 hour, stopping heating and cooling to 50 ℃, adding 1.2g of zirconium nitrate and 13g of sodium nitrate, stirring for 30 minutes, cooling to 30 ℃, adding 10g of acetic acid, stirring for 10 minutes, adding pure water to 1000ml of constant volume, and depositing cobalt-free passivation solution on the zinc and zinc alloy surface.

When in use, the pH of the passivating agent solution is regulated to 2.0 by acid (nitric acid) or alkali (NaOH), the galvanized workpiece (the thickness of the galvanized layer is more than 6 mu m) is passivated at 25 ℃, the passivation time is 60 seconds, after the passivation is finished, hot water is sealed for 30 seconds at 60-70 ℃, and the iridescent passivation part is obtained after drying at 70-80 ℃.

The zinc and zinc alloy surface of the invention is deposited with the cobalt-free passivation solution, and the galvanized workpiece is passivated at the room temperature of more than 25 ℃ for 30-90s. The galvanized workpiece is detected by the IEC62321 method of SGS, and after the workpiece is placed for 2 months, the Cr6 ten content still does not exceed the Japanese monitoring standard by 2ppm. The work piece is placed for 2 months, and the work piece is not reddish after being boiled in water.

According to GB/T10125-1997 artificial atmosphere corrosion salt spray test, the neutral salt spray test time reaches 240 hours (white rust) under the condition that the outer layer is not sealed (optimal state: cyanide-free alkaline hanging galvanization, automatic line operation and passivation working solution Zn < 2+ > is not beyond the standard range).

The appearance of the passivation layer is bright in color and high in brightness.

Inventive example 2:

adding 500g of pure water, heating to 80 ℃, dissolving chromium trichloride hexahydrate containing 16.7g of chromium into the pure water under continuous stirring, adding 3g of tartaric acid, stirring and dissolving, preserving heat for 30 minutes at 80 ℃, then adding 10-15g of 20% concentration sodium hydroxide solution, adjusting the PH to 2.4-2.6, sequentially adding 0.42g of sodium fluoride and 5.6g of ammonium fluoborate, preserving heat for 2 hours at 80 ℃, cooling to 60 ℃, adding 0.65g of vanadyl sulfate, adding 0.6g of 98% sulfuric acid after the raw materials are completely dissolved, fully reacting for 0.5 hours, cooling to 60 ℃, adding 0.9g of NTA, preserving heat for 1 hour, stopping heating and cooling to 50 ℃, adding 1.2g of zirconium nitrate and 13g of sodium nitrate, stirring for 30 minutes, cooling to 30 ℃, adding 10g of acetic acid, stirring for 10 minutes, adding 1000ml of pure water, and fixing the volume, thus obtaining the cobalt-free passivation solution deposited on the surfaces of zinc and zinc alloy.

The zinc and zinc alloy surface of the invention is deposited with the cobalt-free passivation solution, and the galvanized workpiece is passivated at the room temperature of more than 25 ℃ for 30-90s. The galvanized workpiece is detected by the IEC62321 method of SGS, and after the workpiece is placed for 2 months, the Cr6 ten content still does not exceed the Japanese monitoring standard by 2ppm. The workpiece is placed for 2 months, the workpiece is not reddened after being boiled in water, and the hexavalent chromium is detected to be negative.

Inventive example 3:

adding 500g of pure water, heating to 80 ℃, continuously stirring, dissolving 30g of chromium-containing potassium chromium sulfate in the pure water, adding 3g of tartaric acid, stirring for dissolving, keeping the temperature at 80 ℃ for 30 minutes, then adding 10-15g of 20% concentration sodium hydroxide solution, adjusting the pH to 2.4-2.6, sequentially adding 0.42g of sodium fluoride and 5.6g of ammonium fluoborate, keeping the temperature at 80 ℃ for 2 hours, cooling to 60 ℃, adding 0.65g of vanadyl sulfate, adding 0.6g of 98% sulfuric acid after the raw materials are completely dissolved, fully reacting for 0.5 hours, cooling to 60 ℃, adding 0.9g of NTA, keeping the temperature for 1 hour, stopping heating and cooling to 50 ℃, adding 1.2g of zirconium nitrate and 13g of sodium nitrate, stirring for 30 minutes, cooling to 30 ℃, adding 10g of acetic acid, stirring for 10 minutes, adding pure water to 1000ml of constant volume, and obtaining the zinc and zinc alloy surface deposited cobalt-free passivation solution.

The use conditions and analysis of the cobalt-free passivation solution deposited on the surface of zinc and zinc alloy with different chromium ion concentrations and vanadium ion concentrations are as follows:

the passivation layer of each test panel was carried out at 25 ℃ (surface 1 dm 2PH2.0, time 60 seconds.) and then removed by dipping in 20% hydrochloric acid. 100ml of this solution was taken for analysis and the elemental chromium and vanadium were analyzed by ICP, so the relative proportions of chromium and vanadium in the passivation layer were determined.

Example 4

The appearance of the passivation layer is bright in color and high in brightness. Vanadium content 0.5 g/kg and chromium content 30 g/kg.

Example 5

The appearance of the passivation layer is bright in color and high in brightness. The concentrate contained 0.72 g/kg and 30 g/kg chromium as vanadium.

Example 6

The appearance of the passivation layer is bright in color and high in brightness. Vanadium content 1.02 g/kg and chromium content 30 g/kg.

Example 7

The appearance of the passivation layer is bright in color and high in brightness. Vanadium containing 1.24 g/kg and chromium containing 26 g/kg. .

Example 8

The appearance of the passivation layer is bright in color and high in brightness. Vanadium-containing 2.23 g/kg and chromium-containing 26 g/kg.

Example 9

The appearance of the passivation layer is bright in color and high in brightness. Vanadium containing 3.1 g/kg and chromium containing 35 g/kg.

In examples 4-9 of the present invention, the passivation test 1000 ml/l batch concentration chart data is as follows:

passivation is from 0.05 to 0.5 mg/L of chromium and vanadium containing 3 to 4g/L, thus, correspondingly, the chromium content in the passivation solution, such as the passivation of prior art galvanized sheet passivated with cobalt, is at pH2.0 and 25 ℃ for 60 seconds. The appearance of the passivation film is yellow-green. Passivation ICP analysis showed a chromium content of 0.98 mg/dm 2 and a vanadium content of 0.71 mg/dm 2, so that the chromium-vanadium ratio of 1.35 was free of zinc corrosion during the test after salt spray test according to DIN EN ISO 9227 360 hours.

Comparative example 1

For comparison, a passivation containing cobalt was added thereto. Cobalt sulfate was used instead of vanadyl sulfate.

When in use, the pH of the passivating agent solution is regulated to 2.0 by acid (nitric acid) or alkali (NaOH), the galvanized workpiece (the thickness of the galvanized layer is more than 6 mu m) is passivated at 20-50 ℃, the passivation time is 30-60 seconds, after the passivation is finished, hot water at 60-70 ℃ is sealed for 30 seconds, and the iridescent passivation part is obtained by drying at 70-80 ℃.

The high corrosion-resistant trivalent chromium color passivating agent is used for passivating a galvanized workpiece at the room temperature of more than 25 ℃ for 30-60 seconds. The galvanized workpiece is detected by the IEC62321 method of SGS, and after the workpiece is placed for 2 months, the Cr6 ten content still does not exceed the Japanese monitoring standard by 2ppm. The work piece is placed for 2 months, and the work piece is not reddish after being boiled in water.

According to GB/T10125-1997 artificial atmosphere corrosion salt spray test, the neutral salt spray test time reaches 200 hours (white rust) under the condition that the outer layer is not sealed (optimal state: cyanide-free alkaline hanging galvanization, automatic line operation and passivation working solution Zn < 2+ > is not beyond the standard range).

The appearance of the passivation layer is bright in color and high in brightness. .

Comparative example 2

Comparative example 3

Comparative example 4

Comparative example 5

For comparison, cobalt sulfate and vanadyl sulfate were omitted.

Corrosion occurred in the boundary zone of the test piece after passing DIN EN ISO 9227 for a test period of 8 hours and about 20% surface strong zinc corrosion occurred during 96 hours of the test. The results of comparative examples 5 and 4 show that no cobalt sulfate can be added, resulting in improved corrosion resistance of the passivation. The passivation solution containing cobalt sulfate or vanadyl sulfate can significantly further increase corrosion protection.

The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, and still fall within the scope of the invention.

Claims

1. A cobalt-free passivation solution for zinc and zinc alloy surface deposition is characterized in that: comprises chromium compound of Cr3+258-35g/L, complexing agent 40-70g/L, organic acid 50-90g/L, inorganic acid 20-70g/L, inorganic salt 65-102g/L and water.

2. The zinc and zinc alloy surface deposition cobalt-free passivation solution according to claim 1, wherein: the complexing agent is sodium fluoride or ammonium fluoborate.

3. The zinc and zinc alloy surface deposition cobalt-free passivation solution according to claim 1, wherein: the chromium compound is one or more than two of chromium nitrate, potassium chromium sulfate or chromium chloride.

4. The zinc and zinc alloy surface deposition cobalt-free passivation solution according to claim 1, wherein: the inorganic salt is one or more than two of sodium sulfate, vanadyl sulfate or zirconium sulfate.

5. The zinc and zinc alloy surface deposition cobalt-free passivation solution according to claim 1, wherein: the organic acid is one or more than two of oxalic acid dihydrate, tartaric acid, malonic acid, citric acid, glacial acetic acid, lactic acid or amino acetic acid.

6. The zinc and zinc alloy surface deposition cobalt-free passivation solution according to claim 1, wherein: the inorganic acid is sulfuric acid or nitric acid.

7. The method for preparing the passivation solution without cobalt deposited on the surface of zinc and zinc alloy according to claim 1, comprising the following steps:

adding 500g of pure water, heating to 80 ℃, continuously stirring, dissolving 23g of chromium nitrate containing chromium in the pure water, adding 3g of tartaric acid, stirring and dissolving, keeping the temperature at 80 ℃ for 30 minutes, then adding 10-15g of 20% concentration sodium hydroxide solution, adjusting the pH to 2.4-2.6, sequentially adding 0.42g of sodium fluoride and 5.6g of ammonium fluoborate, keeping the temperature at 80 ℃ for 2 hours, cooling to 60 ℃, adding 0.65g of vanadyl sulfate, adding 0.6g of 98% sulfuric acid after the raw materials are completely dissolved, fully reacting for 0.5 hours, cooling to 60 ℃, adding 0.9g of NTA, keeping the temperature for 1 hour, stopping heating and cooling to 50 ℃, adding 1.2g of zirconium nitrate and 13g of sodium nitrate, stirring for 30 minutes, cooling to 30 ℃ and adding 10g of acetic acid, stirring for 10 minutes, and adding the pure water to 1000ml of constant volume, thus obtaining the cobalt-free passivation solution for zinc and zinc alloy surface deposition.