A method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface

Abstract

The present invention provides a method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface, comprising the following steps: step 1, surface pretreatment: mechanically treating the surface of the steel substrate to remove the oxide layer and oil stains to ensure surface cleanliness, and enhancing the roughness of the substrate surface by sandblasting or laser treatment to improve the adhesion of the ceramic composite layer; step 2, ceramic composite coating preparation: using a spraying method to evenly coat a composite slurry containing acid-resistant ceramic particles on the surface of the steel substrate, the ceramic particles used are selected from aluminum oxide, titanium oxide or silicon nitride materials; step 3, heat treatment and curing. Compared with the prior art, the present invention has the following beneficial effects: its acid resistance and high temperature resistance are much better than traditional materials, the ceramic coating has stronger corrosion resistance in a strong acid environment, and can effectively avoid corrosion of the substrate.

Description

Technical Field

[0001] The invention belongs to the technical field of surface treatment, and is particularly suitable for corrosion protection of steel materials in acidic environments, and particularly relates to a method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface. Background Art

[0002] At present, steel materials are widely used in various engineering fields, but their corrosion resistance in strong acidic environments is poor, and they are prone to corrosion and oxidation, which greatly shortens the service life of steel structures. Traditional anti-corrosion measures include galvanizing, coating, and surface heat treatment, but these methods have more or less disadvantages such as insufficient corrosion resistance, high cost, and poor adhesion. Therefore, the development of a ceramic composite layer with excellent acid resistance and a manufacturing method that can be effectively combined with a steel substrate has become an important direction of current surface treatment technology research. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface to solve the problems raised in the above-mentioned background technology.

[0004] The present invention is achieved through the following technical solution: a method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface, comprising the following steps:

[0005] Step 1, surface pretreatment: Mechanically treat the surface of the steel substrate to remove the oxide layer and oil stains to ensure the surface is clean, and enhance the roughness of the substrate surface by sandblasting or laser treatment to improve the adhesion of the ceramic composite layer;

[0006] Step 2, preparation of ceramic composite coating: using a spraying method to evenly coat the composite slurry containing acid-resistant ceramic particles on the surface of the steel substrate, the ceramic particles used are selected from aluminum oxide, titanium oxide or silicon nitride;

[0007] Step 3, heat treatment and curing: The coated steel substrate is heat treated and cured at a temperature ranging from 500°C to 800°C for 30 minutes to 2 hours to ensure the density and adhesion of the ceramic composite layer.

[0008] As a preferred embodiment, after heat treatment and curing, the cured composite coating is subjected to an acid resistance test, including an immersion test and an acid mist corrosion test, to detect the corrosion performance of the coating in different acidic environments.

[0009] As a preferred embodiment, in step 1, the specific steps of surface pretreatment are:

[0010] Step 1.1, cleaning the substrate surface: clean the steel substrate surface by soaking in chemical cleaning agents or mechanical polishing and sandblasting to remove oxides, oil stains, rust impurities. For the oxide layer on the surface of the steel substrate, use the pickling process to remove it to improve the surface roughness of the steel and enhance the adhesion of the ceramic coating.

[0011] Step 1.2, enhancing surface roughness: enhancing the surface roughness of the steel substrate through a laser treatment process so that the surface roughness Ra value is between 0.8 and 1.5 μm.

[0012] Laser surface treatment can effectively change the surface morphology of steel, forming a micron-level concave-convex structure, which helps the ceramic coating to bond tightly.

[0013] As a preferred embodiment, in step 2, the specific steps of preparing the ceramic composite coating are:

[0014] Step 2.1, ceramic composite material selection: use one or more of alumina, silicon nitride, titanium oxide or magnesium aluminum spinel, add silicone resin to enhance the density and adhesion of the coating,

[0015] Step 2.2, coating: The ceramic composite material is sprayed onto the surface of the steel substrate by a plasma spraying method. During the spraying process, the ceramic particles melt at high temperature, cool rapidly and adhere to the surface of the substrate to form a dense coating. During the spraying process, the coating thickness is between 30 μm and 200 μm.

[0016] As a preferred embodiment, step 2.2, the specific steps of coating are:

[0017] Step 2.21, Surface preheating Before spraying, preheat the surface of the steel substrate at a temperature between 100°C and 250°C. Preheating can reduce the temperature difference between the coating and the substrate surface, avoiding cracking or poor adhesion of the coating due to excessive temperature difference. At the same time, preheating can also make it easier for ceramic particles to adhere to the surface during the spraying process.

[0018] Step 2.22, spraying operation: add the prepared ceramic composite slurry into the spraying equipment, and spray the ceramic slurry onto the surface of the steel substrate through a spray gun. During the spraying process, keep the distance between the spray gun and the substrate surface between 100 mm and 200 mm, and the spraying angle between 45° and 60° to ensure that the coating evenly covers the entire substrate surface.

[0019] As a preferred embodiment, step 2.22, during the spraying operation: the spraying speed is between 3m / s and 5m / s, avoiding the uneven coating caused by too fast spraying speed, or too slow spraying speed caused by too thick coating, and the thickness of the coating is controlled by adjusting the number of coatings and the spraying time during spraying. The coating thickness is between 30μm and 200μm. Thinner coatings are suitable for mildly acidic environments, while thicker coatings are suitable for highly corrosive acidic environments. To ensure the uniformity of the coating, the spraying process should avoid the phenomenon of spraying dead corners or excessive coating accumulation. The rotary spraying technology is used, even if the spray gun rotates and maintains a certain angle, so as to evenly distribute the ceramic coating and avoid local excessive thickness or thinness.

[0020] Step 3, the specific steps of heat treatment curing are:

[0021] After coating the ceramic composite layer, the steel substrate is placed in a high-temperature furnace for heat treatment and curing. The heat treatment temperature is controlled between 500°C and 800°C for 30 minutes to 2 hours. During the heat treatment process, the binder in the ceramic coating will undergo a chemical reaction and solidify into a hard coating, which will form a strong bonding force with the surface of the steel substrate to ensure the adhesion between the ceramic composite layer and the steel substrate.

[0022] The atmosphere during the heat treatment process uses nitrogen. An inert atmosphere (such as nitrogen) helps to avoid oxidation of the coating and improve the density and acid resistance of the coating.

[0023] After adopting the above technical solution, the beneficial effects of the present invention are:

[0024] Compared with existing coating technologies (such as galvanizing or painting), the present invention uses ceramic composite materials, which are much better than traditional materials in acid resistance and high temperature resistance. Ceramic coatings have stronger corrosion resistance in strong acid environments and can effectively prevent corrosion of the substrate.

[0025] Some coating methods in the prior art (such as spraying or painting) may cause coating peeling during use. However, the present invention can significantly improve the adhesion between the ceramic composite layer and the substrate through heat treatment and surface pretreatment processes, thereby avoiding coating peeling or cracking.

[0026] The present invention is not only suitable for acidic environments, but can also work stably in certain high-temperature environments, meeting the needs of various industrial fields for acid-resistant and high-temperature-resistant materials. DETAILED DESCRIPTION

[0027] 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.

[0028] The present invention provides a technical solution: a method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface, comprising the following steps:

[0029] Step 1, surface pretreatment: Mechanically treat the surface of the steel substrate to remove the oxide layer and oil stains to ensure the surface is clean, and enhance the roughness of the substrate surface by sandblasting or laser treatment to improve the adhesion of the ceramic composite layer;

[0030] Step 2, preparation of ceramic composite coating: using a spraying method to evenly coat the composite slurry containing acid-resistant ceramic particles on the surface of the steel substrate, the ceramic particles used are selected from aluminum oxide, titanium oxide or silicon nitride;

[0031] Step 3, heat treatment and curing: The coated steel substrate is heat treated and cured at a temperature ranging from 500°C to 800°C for 30 minutes to 2 hours to ensure the density and adhesion of the ceramic composite layer.

[0032] After heat treatment and curing, the cured composite coating is subjected to acid resistance tests, including immersion tests and acid mist corrosion tests, to detect the corrosion performance of the coating in different acidic environments.

[0033] As an embodiment of the present invention: in step 1, the specific steps of surface pretreatment are:

[0034] Step 1.1, cleaning the substrate surface: clean the steel substrate surface by soaking in chemical cleaning agents or mechanical polishing and sandblasting to remove oxides, oil stains, rust impurities. For the oxide layer on the surface of the steel substrate, use the pickling process to remove it to improve the surface roughness of the steel and enhance the adhesion of the ceramic coating.

[0035] Step 1.2, enhancing surface roughness: enhancing the surface roughness of the steel substrate through a laser treatment process so that the surface roughness Ra value is between 0.8 and 1.5 μm.

[0036] Laser surface treatment can effectively change the surface morphology of steel, forming a micron-level concave-convex structure, which helps the ceramic coating to bond tightly.

[0037] As an embodiment of the present invention: Step 2, the specific steps of preparing the ceramic composite coating are:

[0038] Step 2.1, ceramic composite material selection: use one or more of alumina, silicon nitride, titanium oxide or magnesium aluminum spinel, add silicone resin to enhance the density and adhesion of the coating,

[0039] Step 2.2, coating: The ceramic composite material is sprayed onto the surface of the steel substrate by a plasma spraying method. During the spraying process, the ceramic particles melt at high temperature, cool rapidly and adhere to the surface of the substrate to form a dense coating. During the spraying process, the coating thickness is between 30 μm and 200 μm.

[0040] Step 2.2, the specific steps of coating are:

[0041] Step 2.21, Surface preheating Before spraying, preheat the surface of the steel substrate at a temperature between 100°C and 250°C. Preheating can reduce the temperature difference between the coating and the substrate surface, avoiding cracking or poor adhesion of the coating due to excessive temperature difference. At the same time, preheating can also make it easier for ceramic particles to adhere to the surface during the spraying process.

[0042] Step 2.22, spraying operation: add the prepared ceramic composite slurry into the spraying equipment, and spray the ceramic slurry onto the surface of the steel substrate through a spray gun. During the spraying process, keep the distance between the spray gun and the substrate surface between 100 mm and 200 mm, and the spraying angle between 45° and 60° to ensure that the coating evenly covers the entire substrate surface.

[0043] Step 2.22, during the spraying operation: the spraying speed is between 3m / s and 5m / s. Avoid spraying too fast to cause uneven coating, or too slow to cause too thick coating. The thickness of the coating is controlled by adjusting the number of coatings and the spraying time. The coating thickness is between 30μm and 200μm. Thinner coatings are suitable for mildly acidic environments, while thicker coatings are suitable for highly corrosive acidic environments. To ensure the uniformity of the coating, the spraying process should avoid spraying dead corners or excessive coating accumulation. The rotary spraying technology is used, even if the spray gun rotates and maintains a certain angle, so as to evenly distribute the ceramic coating and avoid local excessive thickness or thinness.

[0044] Step 3, the specific steps of heat treatment curing are:

[0045] After coating the ceramic composite layer, the steel substrate is placed in a high-temperature furnace for heat treatment and curing. The heat treatment temperature is controlled between 500°C and 800°C for 30 minutes to 2 hours. During the heat treatment process, the binder in the ceramic coating will undergo a chemical reaction and solidify into a hard coating, which will form a strong bonding force with the surface of the steel substrate to ensure the adhesion between the ceramic composite layer and the steel substrate.

[0046] The atmosphere during the heat treatment process uses nitrogen. Inert atmosphere (such as nitrogen) helps to avoid oxidation of the coating and improve the density and acid resistance of the coating.

[0047] As an embodiment of the present invention: 1) Surface pretreatment

[0048] The process of the present invention: using the sandblasting method, using brown corundum particles with a particle size of 50 μm to spray onto the surface of the steel plate, the sandblasting pressure is 0.6 MPa. The surface roughness is controlled at Ra 6.5 μm. Then the surface dust is removed and preheated at 100°C.

[0049] Comparison process: Direct surface cleaning (solvent wiping, no sandblasting).

[0050] (2) Coating preparation

[0051] The method of the invention comprises the following steps: using plasma spraying equipment to spray alumina ceramic slurry at 300°C, controlling the spraying thickness to be 150 μm, and heat treating and curing at a temperature of 600°C.

[0052] Comparative method: The ceramic slurry was evenly coated on the surface of the steel plate by brushing and cured at 200°C.

[0053] (3) Test items and methods

[0054] Surface roughness test: measure the surface roughness (Ra value) of the substrate.

[0055] Coating adhesion test: Use a pull-off tester to measure the coating adhesion (unit: MPa) in accordance with ISO 4624 standard.

[0056] Coating hardness test: Use a Vickers hardness tester to measure the hardness of the coating (unit: HV).

[0057] Acid resistance test: The coating samples were immersed in 10% H2SO4 solution and 10% HCl solution, and the coating mass change (weight loss rate) and surface change after 24 hours were observed.

[0058] The above is used to verify the technical effects of the surface pretreatment process of the present invention and the ceramic composite coating prepared by the spraying method in terms of acid resistance, adhesion, coating uniformity, etc., and to compare with the traditional method.

[0059] In the above, the experimental results are shown in Table 1.

[0060] Test items Process of the present invention Comparison process Improved results Surface roughness (Ra, μm) 6.5 1.2 Improve surface adhesion Coating Adhesion(MPa) 23.8 10.5 Increased by 127% Coating hardness (HV) 950 580 64% stronger <![CDATA[Acid resistance (H2SO4, %)]]> Mass loss rate 0.1 Mass loss rate 0.8 Acid resistance increased by 700% Acid resistance (HCl,%) Mass loss rate 0.15 Mass loss rate 0.9 Acid resistance increased by 600% Coating uniformity (visual inspection) Smooth, no obvious defects There is local unevenness The coating is more uniform and dense

[0061] Table 1

[0062] As can be seen from the above table, this process has the following advantages over traditional processes:

[0063] Improved surface roughness: The present invention increases the roughness of the substrate surface (Ra 6.5 μm) by sandblasting, which significantly improves the adhesion of the ceramic coating compared to the comparative process (Ra 1.2 μm), and avoids the problem of easy detachment of the coating in the traditional method.

[0064] Enhanced adhesion: Pull-out test results show that the adhesion of the coating of the present invention reaches 23.8MPa, while the comparative process is only 10.5MPa, an increase of 127%. This improvement is due to the use of surface roughening and high-temperature spraying binder.

[0065] Improved hardness: The hardness of the coating of the present invention reaches 950 HV, which is higher than 580 HV of the comparative process. The main reason is that the high temperature and rapid cooling during the spraying process allows the ceramic particles to form a denser structure.

[0066] Significantly improved acid resistance: Immersion tests in 10% H2SO4 and 10% HCl solutions show that the mass loss rate of the coating of the present invention is as low as 0.1%-0.15%, while the coating loss rate of the comparative process is as high as 0.8%-0.9%, and the acid resistance is improved by 6-7 times. This is due to the uniformity and density of the ceramic layer.

[0067] Better coating uniformity: The present invention achieves uniform distribution of the coating through plasma spraying, avoiding the local over-thickness or over-thinness phenomenon that may occur in the traditional brush coating method, making the coating denser and the surface smoother.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing an acid-resistant ceramic composite layer on a steel-based surface, characterized in that: The following steps are involved: Step 1, surface pretreatment: Mechanically treat the surface of the steel substrate to remove the oxide layer and oil stains to ensure the surface is clean, and enhance the roughness of the substrate surface by sandblasting or laser treatment to improve the adhesion of the ceramic composite layer; Step 2, preparation of ceramic composite coating: using a spraying method to evenly coat the composite slurry containing acid-resistant ceramic particles on the surface of the steel substrate, the ceramic particles used are selected from aluminum oxide, titanium oxide or silicon nitride; Step 3, heat treatment and curing: The coated steel substrate is heat treated and cured at a temperature ranging from 500°C to 800°C for 30 minutes to 2 hours to ensure the density and adhesion of the ceramic composite layer.

2. The method for manufacturing an acid-resistant ceramic composite layer for a steel-based surface according to claim 1, characterized in that: After heat treatment and curing, the cured composite coating is subjected to acid resistance tests, including immersion tests and acid mist corrosion tests, to detect the corrosion performance of the coating in different acidic environments.

3. The method for manufacturing an acid-resistant ceramic composite layer for a steel-based surface according to claim 1, characterized in that: In step 1, the specific steps of surface pretreatment are: Step 1.1, cleaning the substrate surface: clean the steel substrate surface by soaking in chemical cleaning agents or mechanical polishing and sandblasting to remove oxides, oil stains, rust impurities. For the oxide layer on the surface of the steel substrate, use the pickling process to remove it to improve the surface roughness of the steel and enhance the adhesion of the ceramic coating. Step 1.2, enhancing surface roughness: enhancing the surface roughness of the steel substrate through a laser treatment process so that the surface roughness Ra value is between 0.8 and 1.5 μm.

4. The method for manufacturing an acid-resistant ceramic composite layer for a steel-based surface as claimed in claim 3, characterized in that: Step 2: The specific steps of preparing the ceramic composite coating are: Step 2.1, ceramic composite material selection: use one or more of alumina, silicon nitride, titanium oxide or magnesium aluminum spinel, add silicone resin to enhance the density and adhesion of the coating, Step 2.2, coating: The ceramic composite material is sprayed onto the surface of the steel substrate by a plasma spraying method. During the spraying process, the ceramic particles melt at high temperature, cool rapidly and adhere to the surface of the substrate to form a dense coating. During the spraying process, the coating thickness is between 30 μm and 200 μm.

5. The method for manufacturing an acid-resistant ceramic composite layer for a steel-based surface as claimed in claim 4, characterized in that: Step 2.2, the specific steps of coating are: Step 2.21, Surface preheating Before spraying, the surface of the steel substrate is preheated, and the preheating temperature is controlled between 100℃ and 250℃. Step 2.22, spraying operation: add the prepared ceramic composite slurry into the spraying equipment, and spray the ceramic slurry onto the surface of the steel substrate through a spray gun. During the spraying process, keep the distance between the spray gun and the substrate surface between 100 mm and 200 mm, and the spraying angle is 45° to 60°.

6. The method for manufacturing an acid-resistant ceramic composite layer for a steel-based surface as claimed in claim 5, characterized in that: Step 2.22, during the spraying operation: the spraying speed is between 3m / s and 5m / s, the coating thickness is between 30μm and 200μm, and the rotary spraying technology is used, that is, the spray gun rotates and maintains a certain angle, so as to evenly distribute the ceramic coating and avoid local excessive thickness or thinness.

7. A method for manufacturing an acid-resistant ceramic composite layer for a steel-based surface as claimed in claim 1 or 6, characterized in that: Step 3, the specific steps of heat treatment curing are: After coating the ceramic composite layer, the steel substrate is placed in a high-temperature furnace for heat treatment and curing in a nitrogen atmosphere. The heat treatment temperature is controlled between 500°C and 800°C, and the time is 30 minutes to 2 hours. During the heat treatment process, the binder in the ceramic coating will undergo a chemical reaction and solidify into a hard coating, and form a strong bonding force with the surface of the steel substrate, ensuring the adhesion between the ceramic composite layer and the steel substrate.