Chromium-free passivation method for zinc steel guardrail

Abstract

The invention provides a chromate-free passivation method for a zinc steel guardrail. The chromate-free passivation method comprises the steps that the average thickness of a hot galvanizing layer of the zinc steel guardrail is obtained; the passivation temperature is calculated according to a first control formula; the passivation time is calculated according to a second control formula; the zinc steel guardrail is immersed in a chromate-free passivation solution with the temperature of 50 DEG C, and the constant temperature is kept for time; and the zinc steel guardrail subjected to chromium-free passivation is taken out and dried, and a passivation film is formed on the hot galvanizing layer of the zinc steel guardrail in a curing mode. A chromium-free passivation system is adopted to meet the requirements of environmental protection laws and regulations, a correlation model of the average thickness of a hot galvanizing layer, the passivation temperature and the passivation time is established, passivation process parameter adaptation is achieved, the uniformity of the density and the adhesive force of a passivation film is remarkably improved, the corrosion resistance stability of guardrail products of different batches and different parts is guaranteed, and the service life of the guardrail products is prolonged. The service life of the zinc steel guardrail is prolonged, and meanwhile the core characteristics of high strength, high rigidity and the like are maintained.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to a chromium-free passivation method for zinc-steel guardrails. Background Technology

[0002] Zinc-steel guardrails are widely used in municipal construction, real estate, and transportation facilities due to their high strength, high rigidity, aesthetic appeal, and durability. Hot-dip galvanizing is the core method for improving the corrosion resistance of zinc-steel guardrails, while passivation treatment, as a key process after hot-dip galvanizing, can form a dense passivation film on the zinc layer surface, further isolating corrosive media such as air and moisture, and significantly extending the service life of the guardrails.

[0003] Traditional passivation processes use chromate passivation solutions primarily composed of hexavalent or trivalent chromium. While these processes can form passivation films with excellent self-healing capabilities, hexavalent chromium is highly toxic and carcinogenic, and the treatment of chromium-containing wastewater is costly, posing a serious threat to the environment and human health. With increasingly stringent global environmental regulations, developing environmentally friendly chromium-free passivation technologies has become an inevitable trend in the industry.

[0004] Currently, chromium-free passivation technology has made some progress. However, existing chromium-free passivation processes use fixed passivation parameters or are adjusted based on experience, making it difficult to form an optimal passivation film for all thicknesses of zinc plating, thus affecting the overall corrosion resistance uniformity and reliability of the guardrail product. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a chromium-free passivation method for zinc-steel guardrails, which improves the stability and batch consistency of the passivation film performance of zinc-steel guardrails while achieving environmental protection goals.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a chromium-free passivation method for zinc-steel guardrails, the method comprising: S1: Obtain the average thickness of the hot-dip galvanized layer on the zinc-steel guardrail. .

[0007] S2: Calculate the passivation temperature according to the first control formula. The first control formula is: in, The first adjustment factor is... This is the reference temperature.

[0008] The passivation time is calculated according to the second control formula. The second control formula is: in, This is the second adjustment factor; Used as the base time.

[0009] S3: Immerse the zinc-steel guardrail at a temperature of... In a chromium-free passivation solution, maintain a constant temperature time.

[0010] S4: Take out the chromium-free passivated zinc steel guardrail and dry it to allow the hot-dip galvanized layer of the zinc steel guardrail to solidify and form a passivation film.

[0011] Preferably, the method for obtaining the average thickness of the hot-dip galvanized layer of the zinc-steel guardrail in S1 includes: using a thickness gauge to measure the thickness of the hot-dip galvanized layer at at least 5 detection points on the zinc-steel guardrail, and taking the average value of the hot-dip galvanized layer thickness at at least 5 detection points as the average thickness of the hot-dip galvanized layer of the zinc-steel guardrail.

[0012] Preferably, S1 further includes: if the average thickness of the hot-dip galvanized layer of the zinc-steel guardrail is not less than a set thickness threshold, then S2 is executed; if the average thickness of the hot-dip galvanized layer of the zinc-steel guardrail is less than the set thickness threshold, then the zinc-steel guardrail is marked as a defective product.

[0013] Preferably, the set thickness threshold is 60–80 μm.

[0014] Preferably, in the first control formula, It is 0.17–0.18℃ / μm; The temperature ranges from 8.5 to 9.5℃.

[0015] Preferably, in the second control formula, The value is 0.02–0.03 min / μm; The time is 0.5 to 0.6 minutes.

[0016] Preferably, the chromium-free passivation solution in S3 is a zirconium-titanium composite chromium-free passivation solution, and its components and mass concentrations are as follows: fluorozirconic acid: 5.0-8.0 g / L; fluorotitanic acid: 3.0-5.0 g / L; nitric acid: 2.5-4.0 g / L; citric acid: 1.8-3.0 g / L; cobalt nitrate: 0.8-1.5 g / L; silane coupling agent: 0.5-1.2 g / L; the balance is deionized water.

[0017] Preferably, the drying temperature in S4 is 60–80°C.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: In the chromium-free passivation method of zinc steel guardrail of the present invention, the chromium-free passivation system meets the requirements of environmental protection regulations, establishes a correlation model between the average thickness of the hot-dip galvanized layer and the passivation temperature and time, realizes the adaptation of passivation process parameters, significantly improves the uniformity of passivation film density and adhesion, ensures the stability of corrosion resistance of guardrail products of different batches and different parts, and maintains its core characteristics such as high strength and high rigidity while extending the service life of zinc steel guardrail. Attached Figure Description

[0019] Figure 1 This is a flowchart of a chromium-free passivation method for zinc-steel guardrails according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It is understood that, without conflict, some technical means of the various embodiments described herein can be substituted for or combined with each other.

[0021] In the description of this invention, the terms "first," "second," etc., are used only to distinguish the described objects and have no sequential or technical meaning. Therefore, objects specified with "first," "second," etc., may explicitly or implicitly include one or more of those objects. Furthermore, the words "one" or "a" do not indicate a quantity limitation, but rather indicate the presence of at least one, while "multiple" indicates at least two.

[0022] In the description of this invention, references to "one embodiment" or "some embodiments" mean that one or more embodiments of the invention include a particular feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "one embodiment," "some embodiments," "other embodiments," "and other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0023] This invention provides a chromium-free passivation method for zinc-steel guardrails, referring to... Figure 1 The chromium-free passivation method for this zinc-steel guardrail includes: S1: Obtain the average thickness of the hot-dip galvanized layer on the zinc-steel guardrail. .

[0024] S2: Calculate the passivation temperature according to the first control formula. The first control formula is: in, The first adjustment factor is... This is the reference temperature.

[0025] The passivation time is calculated according to the second control formula. The second control formula is: in, This is the second adjustment factor; Used as the base time.

[0026] S3: Immerse the zinc-steel guardrail at a temperature of... In a chromium-free passivation solution, maintain a constant temperature time.

[0027] S4: Take out the chromium-free passivated zinc steel guardrail and dry it to allow the hot-dip galvanized layer of the zinc steel guardrail to solidify and form a passivation film.

[0028] In the chromium-free passivation method for zinc-steel guardrails of the present invention, a chromium-free passivation system is adopted to meet environmental protection regulations. A correlation model is established between the average thickness of the hot-dip galvanized layer and the passivation temperature and time, so as to achieve the adaptation of passivation process parameters, significantly improve the uniformity of passivation film density and adhesion, ensure the stability of corrosion resistance of guardrail products in different batches and different parts, and maintain its core characteristics such as high strength and high rigidity while extending the service life of zinc-steel guardrails.

[0029] Tests have verified that the porosity of the passivation film on zinc-steel guardrails treated with this method can be reduced to below 3%, and the adhesion level can reach Grade 1. Compared with the passivation process with fixed parameters, the overall corrosion resistance life of the product is extended by more than 30%.

[0030] In some embodiments, the method for obtaining the average thickness of the hot-dip galvanized layer of the zinc-steel fence in S1 includes: measuring the thickness of the hot-dip galvanized layer at at least five detection points on the zinc-steel fence using a thickness gauge, and taking the average thickness of the hot-dip galvanized layer at the at least five detection points as the average thickness of the hot-dip galvanized layer of the zinc-steel fence. The thickness gauge can be a product such as an eddy current thickness gauge or a magnetic thickness gauge, which are products of the prior art. It should be noted that the selection of detection points in this step needs to cover the key parts of the zinc-steel fence to ensure that the measurement results reflect the overall state of the hot-dip galvanized layer.

[0031] In some embodiments, S1 further includes: if the average thickness of the hot-dip galvanized layer of the zinc-steel guardrail is not less than a set thickness threshold, then S2 is executed; if the average thickness of the hot-dip galvanized layer of the zinc-steel guardrail is less than the set thickness threshold, then the zinc-steel guardrail is marked as a defective product. Adding a thickness screening step can preemptively remove products with insufficient galvanized layer thickness, avoiding ineffective investment in subsequent passivation processes, while ensuring that products entering the passivation process have basic corrosion resistance; defective products can be returned to the hot-dip galvanizing process for reprocessing, improving raw material utilization and reducing production costs.

[0032] Furthermore, the thickness threshold can be set to 60–80 μm. For example, in scenarios with relatively mild corrosive environments such as municipal roads and inland production areas, 60 μm can be selected as the thickness threshold; in scenarios with harsh corrosive environments such as coastal areas and industrial zones, 80 μm can be selected as the thickness threshold to ensure the basic protective capability of the hot-dip galvanized layer.

[0033] In some embodiments, in the first control formula, It is 0.17–0.18℃ / μm; The temperature ranges from 8.5 to 9.5℃.

[0034] Furthermore, in the second control formula, The value is 0.02–0.03 min / μm; The time is 0.5 to 0.6 minutes.

[0035] The settings of the first adjustment coefficient, reference temperature, second adjustment coefficient, and reference time mentioned above can improve the passivation effect, ensure the stability of the passivation film, and control production costs.

[0036] In some embodiments, the chromium-free passivation solution in S3 is a zirconium-titanium composite chromium-free passivation solution, with the following components and mass concentrations: fluorozirconic acid: 5.0–8.0 g / L; fluorotitanic acid: 3.0–5.0 g / L; nitric acid: 2.5–4.0 g / L; citric acid: 1.8–3.0 g / L; cobalt nitrate: 0.8–1.5 g / L; silane coupling agent: 0.5–1.2 g / L; the balance is deionized water. Fluorozirconic acid and fluorotitanic acid are the main components for film formation, and their synergistic effect can form a zirconium-titanium composite oxide film, effectively improving the corrosion resistance of the zinc-steel guardrail. Nitric acid is used to adjust the pH of the chromium-free passivation solution to 2.0–3.0, providing a suitable acidic environment for the film formation reaction. Citric acid, as a complexing agent, can form stable complexes with zirconium and titanium ions, preventing premature precipitation and extending the service life of the passivation solution. Cobalt ions in cobalt nitrate can be embedded in the passivation film, improving the electrochemical stability of the film layer. Silane coupling agents enhance the adhesion between the passivation film and the zinc layer, while also improving the wear resistance of the film. The precise proportions of the above components ensure the stability and reactivity of the passivation solution.

[0037] In some embodiments, the drying temperature in step S4 is 60–80°C, and the drying time is 15–30 minutes. Suitable drying temperature and time ensure sufficient curing of the passivation film, improve adhesion, and prevent stress concentration within the film layer. The hardness of the dried passivation film can reach HV300 or higher, effectively resisting mechanical damage during transportation and installation. Example 1:

[0038] Chromium-free passivation methods for zinc-steel guardrails include: S1: The thickness of the hot-dip galvanized layer was measured at five points on the zinc-steel guardrail: both ends, the middle part, the corners, and the weld. The thicknesses at each point were 73μm, 76μm, 74μm, 77μm, and 75μm, respectively. The average thickness of the hot-dip galvanized layer of the zinc-steel guardrail was calculated to be 75μm.

[0039] S2: In the first control formula, the first adjustment coefficient is set. It is 0.178℃ / μm, with a reference temperature. The passivation temperature is calculated to be 9.2℃. The temperature is 22.55℃. In the second control formula, a second adjustment coefficient is set. 0.028 min / μm; reference time The passivation time was calculated to be 0.58 min. It takes 2.68 minutes.

[0040] S3: Immerse the zinc-steel guardrail in a chromium-free passivation solution at a temperature of 22.55℃ and maintain the temperature for 2.68 minutes.

[0041] S4: Take out the chromium-free passivated zinc steel guardrail and dry it at 60-65℃ for 15-30 minutes to solidify and form a passivation film on the hot-dip galvanized layer of the zinc steel guardrail.

[0042] Tests showed that the passivation film had a porosity of 2.0% and an adhesion grade of 1; the time to white rust appeared in the neutral salt spray test was 520 hours; the tensile strength of the zinc-steel guardrail was above 425 MPa and the bending strength was above 585 MPa. Example 2:

[0043] Chromium-free passivation methods for zinc-steel guardrails include: S1: The thickness of the hot-dip galvanized layer was measured at five points on the zinc-steel guardrail: both ends, the middle part, the corners, and the weld. The thicknesses at each point were 102μm, 106μm, 104μm, 108μm, and 105μm, respectively. The average thickness of the hot-dip galvanized layer of the zinc-steel guardrail was calculated to be 105μm.

[0044] S2: In the first control formula, the first adjustment coefficient is set. It is 0.172℃ / μm, with a reference temperature. The passivation temperature is calculated to be 8.8℃. The temperature is 26.86℃. In the second control formula, a second adjustment coefficient is set. 0.023 min / μm; reference time The passivation time was calculated to be 0.53 min. It takes 3.04 minutes.

[0045] S3: Immerse the zinc-steel guardrail in a chromium-free passivation solution at a temperature of 26.86℃ and maintain the temperature for 3.04 minutes.

[0046] S4: Take out the chromium-free passivated zinc steel guardrail and dry it at 60-65℃ for 15-30 minutes to solidify and form a passivation film on the hot-dip galvanized layer of the zinc steel guardrail.

[0047] Tests showed that the passivation film had a porosity of 1.7% and an adhesion grade of 1; the time for white rust to appear in the neutral salt spray test was 680 hours; and the tensile strength of the zinc-steel guardrail was above 430 MPa and the bending strength was above 590 MPa.

[0048] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A chromium-free passivation method for zinc steel guardrails, characterized in that: The chromium-free passivation method of the zinc steel guardrail comprises the following steps: S1 : Obtain the average thickness of the hot-dip galvanizing layer of the zinc steel guardrail ; S2: calculating the passivation temperature according to a first control formula , the first control formula being: wherein, is a first adjustment coefficient, is a reference temperature; calculating the deactivation time according to a second control formula , the second control formula being: wherein, is a second adjustment coefficient; is a reference time; S3: Immersing the zinc steel guardrail into a chromium-free passivation solution with a temperature of 40-50°C, keeping constant temperature for 10-20 minutes. minutes.​ S4: taking out the zinc steel guardrail after chromium-free passivation and drying, so as to solidify the passivation film on the hot-dip galvanized layer of the zinc steel guardrail.

2. The method of claim 1, wherein the zinc steel guardrail is a galvanized steel guardrail. The method for obtaining the average thickness of the hot-dip galvanized layer of the zinc steel guardrail in S1 comprises the following steps: using a thickness gauge to measure the thickness of the hot-dip galvanized layer at at least 5 detection points of the zinc steel guardrail, and taking the average value of the thickness of the hot-dip galvanized layer at the at least 5 detection points as the average thickness of the hot-dip galvanized layer of the zinc steel guardrail.

3. The method of claim 1, wherein the zinc steel guardrail is a galvanized steel guardrail. S1 further comprises: if the average thickness of the hot-dip galvanized layer of the zinc steel guardrail is not less than a set thickness threshold, performing S2; and if the average thickness of the hot-dip galvanized layer of the zinc steel guardrail is less than the set thickness threshold, marking the zinc steel guardrail as unqualified product.

4. The method of claim 3, wherein the zinc steel guardrail is a galvanized steel guardrail. The set thickness threshold is 60-80 μm.

5. The method of claim 1, wherein the zinc steel guardrail is a galvanized steel guardrail. In the first control formula, is 0.17-0.18°C / μm; is 8.5-9.5°C.

6. The method of claim 1, wherein the zinc steel guardrail is a galvanized steel guardrail. In the second control formula, is 0.02 to 0.03 min / μm; is 0.5 to 0.6 min.

7. The method of claim 1, wherein the zinc steel guardrail is a galvanized steel guardrail. The chromium-free passivation liquid in S3 is a zirconium-titanium composite chromium-free passivation liquid, and the components and mass concentrations thereof are as follows: fluorozirconic acid: 5.0-8.0 g / L; fluorotitanic acid: 3.0-5.0 g / L; nitric acid: 2.5-4.0 g / L; citric acid: 1.8-3.0 g / L; cobalt nitrate: 0.8-1.5 g / L; silane coupling agent: 0.5-1.2 g / L; and the rest is deionized water. The temperature of drying in S4 is 60-80 °C. ​ 8. The method of claim 1, wherein the zinc steel guardrail is a galvanized steel guardrail. ​

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