Method for detecting ammonium-zinc ion ratio of galvanizing assistant agent

Abstract

The invention belongs to the technical field of quantitative detection, and particularly discloses a method for detecting the ammonium-zinc ion ratio of a galvanizing assistant agent. The method comprises the following steps: respectively detecting the concentration of ammonium ions and the concentration of zinc ions in the galvanizing assistant agent, and then obtaining the ammonium-zinc ion ratio; the detection method of the zinc ion concentration comprises the following steps: firstly, mixing the zinc plating assistant agent with the composite masking agent, then adjusting the pH value of the first mixed solution to be neutral by utilizing ammonia water, and then mixing with the buffer solution. And titrating the mixed solution by taking an EDTA (Ethylene Diamine Tetraacetic Acid) solution as a titrant and a Cu-EDTA solution as a displacer, and calculating the concentration of the zinc ions when the titration potential suddenly exceeds and the titration end point is reached. According to the method, the masking agent is added before titration, so that the interference of metal hetero-ions in the monitoring process of zinc chloride serving as a zinc plating assistant can be eliminated, an accurate and rapid zinc ion content detection method is provided, and Cu-EDTA can increase the titration jump of the zinc ions and improve the titration accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of quantitative detection, and in particular to a method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent. Background Art

[0002] Hot-dip galvanizing has long been the most widely used process in steel galvanizing. Its coating has good corrosion resistance, controllable thickness and surface morphology, simple process and low cost, and has become an effective method for steel corrosion protection. To obtain a good hot-dip galvanized layer, the pre-treatment of the plated parts is very important. Its main process flow includes: pre-plated parts alkali degreasing-water washing-acid washing and rust removal-water washing-solvent plating-drying-hot-dip galvanizing-cooling-post-treatment and other processes. Among them, the solvent plating process is an important link in the hot-dip galvanizing process and plays a vital role. It refers to the process of immersing the plated parts after alkali washing and acid washing into the plating solution to obtain a uniform plating salt film on the surface of the plated parts. This salt film can remove the oxides on the surface of the plated parts and protect the surface of the plated parts from oxidation before immersion plating; at the same time, it activates the surface of the plated parts, improves the wetting ability of the zinc liquid on the plated parts, and thus improves the adhesion of the coating to the workpiece.

[0003] The commonly used plating aid is a mixed solution of zinc chloride and ammonium chloride in a certain proportion, called ammonium zinc plating aid, which has a history of hundreds of years. Therefore, research reports on the concentration, use temperature and pH value control of the plating aid have been fruitful. For example, the concentration of the plating aid should be controlled at 200g / L~400g / L, and the ammonium zinc ratio is recommended to be 1.2~1.6. High or low will affect the quality of the final plated parts. When the ammonium zinc ratio is less than 1, the salt film formed on the surface of the plated part is easy to absorb moisture in the air and easy to explode zinc during immersion plating. When the ammonium zinc ratio is greater than 2, the large amount of ammonium chloride in the plating aid has poor thermal stability at high temperatures, resulting in poor stability of the salt film on the surface of the plated part, and excessive ammonium chloride during immersion plating will produce a lot of smoke and dust, affecting the health of the operating workers, polluting the environment, and ultimately causing a waste of resources. Although the hot-dip galvanizing process is very mature, the domestic galvanizing industry still relies solely on experience and visual observation for the concentration and ratio of ammonium zinc in the plating agent. There is no formal operating procedure for monitoring the concentration of ammonium zinc in the plating agent. Therefore, the concentration of the plating agent is often not well controlled, which directly affects the quality of galvanizing and production costs, resulting in a waste of resources.

[0004] Therefore, strict control of the concentration of the plating agent and the ratio of ammonium to zinc is of great significance for the production of the hot-dip galvanizing industry. Summary of the invention

[0005] In view of this, the present invention provides a method for detecting the ammonium-zinc ion ratio of a zinc plating auxiliary agent, so as to solve the problem that the monitoring of the ion concentration in the existing zinc plating auxiliary agent is irregular and the ammonium-zinc ion ratio cannot be accurately detected.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent comprises the following steps: respectively detecting the ammonium root ion concentration and the zinc ion concentration in the zinc plating auxiliary agent, and then calculating the ammonium zinc ion ratio according to the ammonium root ion concentration and the zinc ion concentration;

[0008] Wherein, the detection method of the zinc ion concentration comprises the following steps:

[0009] 1) mixing the zinc plating auxiliary agent to be tested with the composite masking agent to obtain a first mixed solution;

[0010] 2) adjusting the pH value of the first mixed solution to neutral with aqueous ammonia, and then mixing with a buffer solution to obtain a second mixed solution;

[0011] 3) The second mixed solution is titrated using EDTA solution as a titrant and Cu-EDTA solution as a displacing agent. When a sudden change occurs in the titration potential and the titration endpoint is reached, the zinc ion concentration is calculated.

[0012] Preferably, the composite masking agent is a mixed solution of ammonium fluoride and sodium tartrate;

[0013] The mass ratio of ammonium fluoride to sodium tartrate in the composite masking agent is 7 to 9:1;

[0014] The mass concentration of ammonium fluoride in the composite masking agent is 0.2-2%.

[0015] Preferably, the volume ratio of the zinc plating auxiliary agent to be tested to the composite masking agent is 50:0.2-5.

[0016] Preferably, the buffer in step 2) is an ammonia-ammonium chloride buffer;

[0017] The volume ratio of the buffer solution to the first mixed solution after adjusting the pH value is 1:1-2.

[0018] Preferably, the titration process in step 3) is to first mix the second mixed solution with the Cu-EDTA solution, and then titrate with the EDTA solution.

[0019] Preferably, the mass concentration of the Cu-EDTA solution is 0.1 to 0.3 mol / L, and the mass concentration of the EDTA solution is 0.1 to 0.5 mol / L;

[0020] The volume ratio of the second mixed solution to the Cu-EDTA solution is 4 to 1:1.

[0021] Preferably, the absolute value of the sudden change in the titration potential is ≥390 mv.

[0022] Preferably, the calculation formula of zinc ion concentration is:

[0023]

[0024] Where:

[0025] C1——molar concentration of EDTA solution, mol / L;

[0026] C2——Zinc ion concentration, mol / L;

[0027] V1——the volume of EDTA solution consumed, mL;

[0028] V2——The volume of the zinc plating agent to be tested, mL.

[0029] Preferably, the ammonium to zinc ion ratio is calculated as ammonium ion concentration / zinc ion concentration.

[0030] Preferably, the zinc plating auxiliary agent is an ammonium zinc plating auxiliary agent.

[0031] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention eliminates the Ca in the zinc plating auxiliary agent zinc chloride monitoring process by adding a masking agent before titration. 2+ Mg 2+ , Fe 2+ , Fe 3+ During the determination process, an appropriate amount of Cu-EDTA solution was added as a replacement agent, and the copper ion selective electrode was used as the indicator electrode. Cu-EDTA can increase the Zn 2+ The titration jump range is reduced, the end point is effectively identified, and the titration accuracy is improved. The invention provides an accurate and rapid method for detecting the content of zinc chloride (zinc ion), which updates the existing method for determining the content of zinc chloride in hot-dip galvanizing auxiliary agent, and largely ensures the quality of galvanizing and saves costs. DETAILED DESCRIPTION

[0033] The invention provides a method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent, comprising the following steps: respectively detecting the ammonium root ion concentration and the zinc ion concentration in the zinc plating auxiliary agent, and then calculating the ammonium zinc ion ratio according to the ammonium root ion concentration and the zinc ion concentration.

[0034] In the present invention, the method for detecting zinc ion concentration comprises the following steps:

[0035] 1) mixing the zinc plating auxiliary agent to be tested with the composite masking agent to obtain a first mixed solution;

[0036] 2) adjusting the pH value of the first mixed solution to neutral with aqueous ammonia, and then mixing with a buffer solution to obtain a second mixed solution;

[0037] 3) Using EDTA solution as titrant and Cu-EDTA solution as displacing agent, the second mixed solution is titrated. When the titration potential jumps and reaches the titration endpoint, the zinc ion concentration is calculated.

[0038] In the present invention, the composite masking agent is a mixed solution of ammonium fluoride and sodium tartrate.

[0039] In the present invention, the mass ratio of ammonium fluoride to sodium tartrate in the composite masking agent is 7 to 9:1, preferably 7.5 to 8.5:1, and more preferably 8:1.

[0040] In the present invention, the mass concentration of ammonium fluoride in the composite masking agent is 0.2-2%, specifically 0.4%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%.

[0041] In the present invention, the volume ratio of the zinc plating auxiliary agent to be tested to the composite masking agent is 50:0.2-5, preferably 50:1-4, and more preferably 50:2.

[0042] In the present invention, the buffer in step 2) is an ammonia-ammonium chloride buffer; the concentration of the ammonia-ammonium chloride buffer is 0.5-1 mol / L, specifically 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L.

[0043] In the present invention, the volume ratio of the buffer solution to the first mixed solution after adjusting the pH value is 1:1-2, preferably 1:1.2-1.8, and more preferably 1:1.5.

[0044] In the present invention, the titration process in step 3) is to first mix the second mixed solution with the Cu-EDTA solution, and then titrate with the EDTA solution.

[0045] In the present invention, the mass concentration of the Cu-EDTA solution is 0.1-0.3 mol / L, specifically 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, 0.2 mol / L, 0.22 mol / L, 0.25 mol / L, 0.28 mol / L; the mass concentration of the EDTA solution is 0.1-0.5 mol / L, specifically 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L.

[0046] In the present invention, the volume ratio of the second mixed solution to the Cu-EDTA solution is 4 to 1:1, preferably 3 to 2:1, and more preferably 2.5:1.

[0047] In the present invention, the absolute value of the jump value when the titration potential jumps is ≥390mv, specifically -400mv, -410mv, -420mv, -430mv; the jump indicates that a sudden change in potential occurs between the previous drop and the next drop.

[0048] In the present invention, the calculation formula of zinc ion concentration is:

[0049]

[0050] Where:

[0051] C1——molar concentration of EDTA solution, mol / L;

[0052] C2——Zinc ion concentration, mol / L;

[0053] V1——the volume of EDTA solution consumed, mL;

[0054] V2——The volume of the zinc plating agent to be tested, mL.

[0055] In the present invention, the calculation method of the ammonium to zinc ion ratio is ammonium ion concentration / zinc ion concentration.

[0056] In the present invention, the zinc plating auxiliary agent is an ammonium zinc plating auxiliary agent.

[0057] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Example 1

[0059] Prepare a zinc-ammonium standard mixed solution at a ratio of zinc chloride: ammonium chloride = 1:1.2. Accurately prepare 250ml solution with a zinc chloride concentration of 0.1mol / L and an ammonium chloride concentration of 0.12mol / L. Add 0.01g of ferrous chloride, 0.01g of ferric chloride, 1.0g of calcium chloride, and 0.2g of magnesium chloride (by adding the above substances, the influence of impurity ions in the zinc plating aid on the test results can be simulated).

[0060] The mixed solution is taken as the zinc plating auxiliary agent to be tested, and the ammonia zinc ion ratio is tested.

[0061] The zinc ion test method is:

[0062] 10 mL of the zinc plating auxiliary agent to be tested was mixed with 0.5 mL of a composite masking agent (the mass ratio of ammonium fluoride to sodium tartrate was 9:1, and the mass concentration of ammonium fluoride was 1.8%) to obtain a zinc plating auxiliary agent containing the composite masking agent; the pH value of the zinc plating auxiliary agent containing the composite masking agent was then adjusted to neutral using ammonia water, and then an ammonia-ammonium chloride buffer solution (concentration of 1 mol / L) was added in a volume ratio of 1:1 to obtain a zinc plating auxiliary agent containing a buffer solution.

[0063] The zinc plating auxiliary agent containing buffer solution was first mixed with 0.2 mol / L Cu-EDTA solution in a volume ratio of 1:1, and a copper ion selective electrode was used as the indicator electrode. Then, 0.1 mol / L EDTA solution was used for titration. When the EDTA solution was titrated to 10.01 mL, a potential jump occurred (the change value was -410 mv), reaching the titration end point. The zinc ion concentration was calculated by the zinc ion concentration formula to obtain a zinc ion concentration of 0.1001 mol / L.

[0064] The ammonium ion test method is:

[0065] Take 10mL of the zinc plating aid to be tested, then add dilute acid to clarify, then add 5ml of formaldehyde solution, and titrate with 0.1mol / L sodium hydroxide solution to pH 6. The volume of sodium hydroxide consumed is 11.98ml. The ammonium ion content in the plating aid solution is calculated to be 0.1198mol / L.

[0066] The ammonium ion concentration / zinc ion concentration gave an ammonia-zinc ion ratio of 1.1968.

[0067] Example 2

[0068] Prepare a zinc-ammonium standard mixed solution at a ratio of zinc chloride: ammonium chloride = 1:1.4. Accurately prepare 250ml solution with a zinc chloride concentration of 0.1mol / L and an ammonium chloride concentration of 0.14mol / L. Add 0.01g of ferrous chloride, 0.01g of ferric chloride, 1.0g of calcium chloride, and 0.2g of magnesium chloride (by adding the above substances, the influence of impurity ions in the zinc plating aid on the test results can be simulated).

[0069] The mixed solution is taken as the zinc plating auxiliary agent to be tested, and the ammonia zinc ion ratio is tested.

[0070] The zinc ion test method is:

[0071] 10 mL of the zinc plating auxiliary agent to be tested was mixed with 0.5 mL of a composite masking agent (the mass ratio of ammonium fluoride to sodium tartrate was 9:1, and the mass concentration of ammonium fluoride was 1.8%) to obtain a zinc plating auxiliary agent containing the composite masking agent; the pH value of the zinc plating auxiliary agent containing the composite masking agent was then adjusted to neutral using ammonia water, and then an ammonia-ammonium chloride buffer solution (concentration of 1 mol / L) was added in a volume ratio of 1:1 to obtain a zinc plating auxiliary agent containing a buffer solution.

[0072] The zinc plating auxiliary agent containing buffer solution was first mixed with 0.2 mol / L Cu-EDTA solution in a volume ratio of 1:1, and a copper ion selective electrode was used as the indicator electrode. Then, 0.1 mol / L EDTA solution was used for titration. When the EDTA solution was titrated to 9.95 mL, a potential jump occurred (the change value was -410 mv), reaching the titration end point. The zinc ion concentration was calculated by the zinc ion concentration formula to obtain a zinc ion concentration of 0.1001 mol / L.

[0073] The ammonium ion test method is:

[0074] Take 10mL of the zinc plating aid to be tested, then add dilute acid to clarify, then add 5ml of formaldehyde solution, and titrate with 0.1mol / L sodium hydroxide solution to pH 6. The volume of sodium hydroxide consumed is 14.02ml. The ammonium ion content in the plating aid solution is calculated to be 0.1402mol / L.

[0075] The ammonium ion concentration / zinc ion concentration gave an ammonia-zinc ion ratio of 1.4090.

[0076] Example 3

[0077] Prepare a zinc-ammonium standard mixed solution at a ratio of zinc chloride: ammonium chloride = 1:1.6. Accurately prepare 250ml solution with a zinc chloride concentration of 0.100mol / L and an ammonium chloride concentration of 0.160mol / L. Add 0.01g of ferrous chloride, 0.01g of ferric chloride, 1.0g of calcium chloride, and 0.2g of magnesium chloride (by adding the above substances, the influence of impurity ions in the zinc plating aid on the test results can be simulated).

[0078] The mixed solution is taken as the zinc plating auxiliary agent to be tested, and the ammonia zinc ion ratio is tested.

[0079] The zinc ion test method is:

[0080] 10 mL of the zinc plating auxiliary agent to be tested was mixed with 0.5 mL of a composite masking agent (the mass ratio of ammonium fluoride to sodium tartrate was 9:1, and the mass concentration of ammonium fluoride was 1.8%) to obtain a zinc plating auxiliary agent containing the composite masking agent; the pH value of the zinc plating auxiliary agent containing the composite masking agent was then adjusted to neutral using ammonia water, and then an ammonia-ammonium chloride buffer solution (concentration of 1 mol / L) was added in a volume ratio of 1:1 to obtain a zinc plating auxiliary agent containing a buffer solution.

[0081] The zinc plating auxiliary agent containing buffer solution was first mixed with 0.2 mol / L Cu-EDTA solution in a volume ratio of 1:1, and a copper ion selective electrode was used as the indicator electrode. Then, 0.1 mol / L EDTA solution was used for titration. When the EDTA solution was titrated to 10.05 mL, a potential jump occurred (the change value was -410 mv), reaching the titration end point. The zinc ion concentration was calculated by the zinc ion concentration formula to obtain a zinc ion concentration of 0.1005 mol / L.

[0082] The ammonium ion test method is:

[0083] Take 10mL of the zinc plating aid to be tested, then add dilute acid to clarify, then add 5ml of formaldehyde solution, and titrate with 0.1mol / L sodium hydroxide solution to pH 6. The volume of sodium hydroxide consumed is 15.89ml. The ammonium ion content in the plating aid solution is calculated to be 0.1589mol / L.

[0084] The ammonium ion concentration / zinc ion concentration gave an ammonia-zinc ion ratio of 1.5810.

[0085] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0086] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent, characterized in that: The method comprises the following steps: respectively detecting the ammonium ion concentration and the zinc ion concentration in the zinc plating auxiliary agent, and then calculating the ammonium zinc ion ratio according to the ammonium ion concentration and the zinc ion concentration; Wherein, the detection method of the zinc ion concentration comprises the following steps: 1) mixing the zinc plating auxiliary agent to be tested with the composite masking agent to obtain a first mixed solution; 2) adjusting the pH value of the first mixed solution to neutral with aqueous ammonia, and then mixing with a buffer solution to obtain a second mixed solution; 3) The second mixed solution is titrated using EDTA solution as a titrant and Cu-EDTA solution as a displacing agent. When a sudden change occurs in the titration potential and the titration endpoint is reached, the zinc ion concentration is calculated.

2. The method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 1, wherein: The composite masking agent is a mixed solution of ammonium fluoride and sodium tartrate; The mass ratio of ammonium fluoride to sodium tartrate in the composite masking agent is 7 to 9:1; The mass concentration of ammonium fluoride in the composite masking agent is 0.2-2%.

3. The detection method of the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 2, characterized in that, The volume ratio of the zinc plating auxiliary agent to be tested to the composite masking agent is 50:0.2-5.

4. A method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to any one of claims 1 to 3, characterized in that: The buffer in step 2) is an ammonia-ammonium chloride buffer; The volume ratio of the buffer solution to the first mixed solution after adjusting the pH value is 1:1-2.

5. The method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 4, wherein: The titration process in step 3) is to first mix the second mixed solution with the Cu-EDTA solution, and then titrate with the EDTA solution.

6. The method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 5, characterized in that: The mass concentration of the Cu-EDTA solution is 0.1-0.3 mol / L, and the mass concentration of the EDTA solution is 0.1-0.5 mol / L; The volume ratio of the second mixed solution to the Cu-EDTA solution is 4 to 1:

1.

7. A method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 5 or 6, characterized in that: When the titration potential has a sudden change, the absolute value of the sudden change is ≥390 mv.

8. The method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 7, characterized in that: The calculation formula of zinc ion concentration is: Where: C1——molar concentration of EDTA solution, mol / L; C2——Zinc ion concentration, mol / L; V1——the volume of EDTA solution consumed, mL; V2——The volume of the zinc plating agent to be tested, mL.

9. The method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 8, characterized in that: The calculation method of the ammonium-zinc ion ratio is ammonium ion concentration / zinc ion concentration.

10. The method for detecting the ammonium zinc ion ratio of a zinc plating auxiliary agent according to claim 9, characterized in that: The zinc plating auxiliary agent is an ammonium zinc plating auxiliary agent.

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