A corrosion-resistant alloy coating and a method of applying the same

Abstract

The present application relates to the field of paint, disclose a kind of corrosion-resistant alloy paint, by coating base material and steel powder, the amount of steel powder is 5%~20% of the weight of coating base material, paint thickness is 120~300 μm, from inside to outside is divided into three thicknesses, the distribution of steel powder in three thicknesses accounts for 10%~20%, 20%~30% and 50%~70% of total amount of steel powder.The corrosion-resistant alloy paint of the present application is sprayed three times, but the coating polymer used is single, there is no obvious interface between coatings due to different materials, and the processing method of the present application, low temperature setting and high temperature curing, further eliminates the interface difference caused by three times spraying, so that the whole coating forms a continuous, uniform whole.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more particularly to a corrosion-resistant alloy coating and its coating method. Background Technology

[0002] In industrial production and daily life, iron-faced structures are ubiquitous, such as bridges, building frames, and machinery. These structures are constantly exposed to air, subject to corrosion from oxygen, moisture, acids, alkalis, and other corrosive media. Currently, the state of iron-faced corrosion protection is not optimistic. While traditional anti-corrosion methods can provide some protection, they have many drawbacks. For example, simple coatings are prone to peeling and cracking over time, exposing the iron surface to corrosive environments again. Furthermore, while hot-dip galvanizing provides better corrosion protection, it is costly and has limitations in applications involving complex iron surfaces.

[0003] Common anti-corrosion paints are divided into water-based paints and oil-based paints. Water-based paints use water as a diluent, offering significant environmental advantages. They release very little organic solvent during application and use, minimizing their impact on indoor and outdoor air quality and effectively reducing health hazards to workers and residents. Water-based paints dry relatively quickly, significantly shortening the application cycle and improving work efficiency. Their coatings also exhibit good water resistance and scrub resistance, making daily cleaning and maintenance convenient. However, water-based paints also have some drawbacks. Their weather resistance is relatively weak; under prolonged sunlight exposure and harsh weather conditions, the coating is prone to chalking and fading. They also have high requirements for the application environment; unsuitable humidity and temperature can easily lead to problems such as sagging and blistering. Oil-based paints, on the other hand, offer excellent gloss and fullness, providing a good decorative effect to iron surfaces, making them look more beautiful and upscale. Their high film hardness, good wear resistance, and chemical resistance provide more durable protection for iron surfaces. They are also highly adaptable to various application environments, ensuring good application quality even under complex conditions. However, oil-based paints contain a large amount of volatile organic solvents, which release a pungent odor during construction, polluting the environment and harming human health; their drying time is long, increasing the waiting time and overall cycle of construction; and they are more expensive, both in terms of the price of the paint itself and the construction cost, compared to water-based paints.

[0004] Therefore, for corrosion protection of iron surfaces in power plants, oil-based paint is significantly more effective than water-based paint. However, the harsh conditions in power plants and the fact that the coating surfaces are mostly curved and have a certain tension make the dried oil-based anti-corrosion paint coating prone to cracking. In particular, to increase corrosion resistance, a certain amount of inorganic particulate matter is usually added. After the paint surface cracks, these inorganic particulate matter will become stress concentration points, accelerating the cracking. In addition, iron components will undergo slight deformation under heat and stress. Due to the significant difference in material between oil-based coatings and iron, repeated deformation will also lead to deeper cracking and even coating peeling off.

[0005] Therefore, an oil-based coating that combines anti-corrosion and mechanical properties is an excellent choice for corrosion protection of metal surfaces in places such as power plants. Summary of the Invention

[0006] To address the problems existing in current coatings for iron surfaces, this invention provides a corrosion-resistant alloy coating, which consists of a coating substrate and steel powder. The amount of steel powder is 5% to 20% of the weight of the coating substrate. The thickness of the corrosion-resistant alloy coating is 120 to 300 μm, and it is divided into three equal thicknesses from the inside out. The steel powder accounts for 10% to 20%, 20% to 30%, and 50% to 70% of the total amount of steel powder in the three thicknesses.

[0007] Furthermore, the steel powder of this invention contains 70wt%~95wt% iron, 2wt%~8wt% manganese, 1wt%~5wt% chromium, 0.5wt%~3wt% silicon, 0.5wt%~0.8wt% phosphorus, 0.2wt%~0.5wt% carbon, and 0.1wt%~0.3wt% boron. A process of rapid cooling after melting yields highly uniform and fine steel powder, exhibiting excellent strength and toughness. Iron is the main component, providing the basic strength of the steel powder; manganese improves the strength and hardness of the steel, enhancing its wear resistance; chromium increases the corrosion resistance of the steel; silicon helps improve the strength and elasticity of the steel; phosphorus and carbon, to some extent, improve the hardness and strength of the steel; and boron refines the grain size, improving the hardenability and toughness of the steel. Adding this specific proportion of steel powder to a polyurethane coating can significantly improve the coating's corrosion resistance and impact resistance.

[0008] Furthermore, the coating substrate is either a polyurethane coating or an epoxy resin coating. Polyurethane coatings possess good flexibility and abrasion resistance. Their molecular structure contains polar groups such as urethane bonds, which provide excellent adhesion between the polyurethane coating and the steel powder. When the steel powder is dispersed in the polyurethane coating, it effectively enhances the coating's strength and toughness. Moreover, the flexibility of the polyurethane coating can buffer external impacts, reducing the likelihood of cracking under external forces. Epoxy resin coatings, on the other hand, exhibit excellent adhesion and chemical resistance. They can firmly adhere to metal surfaces such as iron, forming a tight protective film that prevents oxygen, moisture, and corrosive media from contacting the metal surface. Epoxy resin coatings have good resistance to various chemicals and remain stable in complex chemical environments. When combined with steel powder, the steel powder further enhances the coating's hardness and corrosion resistance.

[0009] Specifically, the polyurethane coating comprises the following components by weight: 60-100 parts of diisocyanate, 70-120 parts of polyol, 20-40 parts of blocked isocyanate, 10-20 parts of organic solvent a, and 0.5-2 parts of catalyst. In each component of the polyurethane coating, the diisocyanate is one of HDI, MDI, IPDI, TDI, or ADI, the polyol is a polyester polyol or a polyether polyol, and the catalyst is an organotin catalyst or an organobismuth catalyst. Epoxy resin coatings comprise the following components by weight: 50-70 parts epoxy resin, 15-30 parts curing agent, 10-20 parts blocked isocyanate, 0-20 parts organic solvent b, 5-10 parts dispersant, and 0.1-2 parts defoamer. In each component of the epoxy resin coating, the curing agent is one or a combination of ethylenediamine, p-phenylenediamine, DETDA, or MDTDA; the dispersant is BYK dispersant or polyamide dispersant; and the defoamer is an organosilicone complex or a non-silicone defoamer.

[0010] Furthermore, organic solvent a and organic solvent b are independently selected from one or more combinations of toluene, butyl acetate, butanol, isopropanol, DMAc, EDGA, DMSO, and PGMEA. The use of organic solvents allows for better and more uniform mixing of the components in the coating substrate, ensuring the dispersion of the steel powder. Suitable organic solvents can adjust the viscosity of the coating, giving it good flowability during spraying and facilitating application. Moreover, different organic solvents have different evaporation rates; by selecting appropriate organic solvents and their combinations, the drying speed of the coating can be controlled to adapt to different application environments and requirements. For example, in high-temperature, well-ventilated environments, a combination of organic solvents with a slightly faster evaporation rate can be selected to accelerate coating drying; while in low-temperature, high-humidity environments, a combination of organic solvents with a slower evaporation rate can be selected to prevent the coating from drying too quickly and causing defects.

[0011] The present invention provides a method for applying the above-mentioned corrosion-resistant alloy coating, comprising the following steps: 1) Weigh out the steel powder and coating substrate components according to the weight requirements. Mix the coating substrate components evenly and divide them into three portions. Add the steel powder to each portion according to the distribution ratio and keep stirring at low temperature. 2) After degassing the mixture from step 1), spray it in order of increasing steel powder content; 3) After the coating is initially solidified with hot air at 50℃~80℃, it is rolled with hot rollers at 120℃~150℃.

[0012] This invention involves uniformly mixing all components of the coating substrate and dividing them into three equal parts. Steel powder is then added to each part in a specific proportion, and the coatings are sprayed sequentially according to the steel powder content, from lowest to highest. This layered coating method creates a gradient structure in the coating. The inner layer has a relatively low steel powder content, ensuring good adhesion between the coating and the metal surface; the outer layer has a higher steel powder content, enhancing the coating's wear and corrosion resistance. This gradient structure design achieves a balance between different performance requirements for the corrosion-resistant alloy coating, ensuring both strong adhesion to the metal surface and improved overall protective performance.

[0013] During the coating process, the coating is initially solidified with hot air at 50℃~80℃, and then rolled with hot rollers at 120℃~150℃. Initial solidification with hot air allows the solvent in the coating to evaporate, forming a preliminary solid structure. Hot roller rolling further compacts the coating, increasing its density, reducing porosity and defects, thereby enhancing its corrosion resistance and mechanical properties. At 120℃~150℃, the hot roller rolling process causes the sealed isocyanates to unblock, releasing diisocyanate groups that react with hydroxyl groups in the system, further strengthening the coating's adhesion and eliminating differences between multiple coating layers, resulting in better overall coating integrity. Furthermore, the repeated heating-cooling cycle of the hot roller rolling process allows the coating to fully react and crystallize, and also allows the steel powder to better bond with the coating substrate, improving the overall uniformity and stability of the coating.

[0014] Compared to existing multi-layer coatings, the corrosion-resistant alloy coating of this invention, although applied in three coats, uses a single polymer, eliminating the distinct interfaces between layers caused by material differences. Furthermore, the low-temperature setting followed by high-temperature curing further eliminates interface differences resulting from the three coats, creating a continuous and uniform coating. Compared to existing single-layer coatings, the proportion of steel powder in this corrosion-resistant alloy coating gradually increases from the inside out. The inner layer has a low steel powder content, ensuring sufficient adhesion between the polymer and the metal surface, while still providing adequate corrosion protection. The outer layers primarily function as corrosion protectants, and the increasing steel powder content precisely meets the demanding corrosion resistance requirements towards the outer edges. This gradient in steel powder content also allows the coating to better disperse stress in the face of external environments, reducing cracking caused by stress concentration. In harsh environments such as power plants, iron surfaces are subjected not only to corrosive media but also to temperature changes and mechanical vibrations. This unique design effectively addresses these complex conditions in the corrosion-resistant alloy coating of this invention. Detailed Implementation

[0015] The present invention will be described below with reference to examples. These examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Example

[0016] A corrosion-resistant alloy coating is composed of a polyurethane coating substrate and steel powder, wherein the amount of steel powder is 12% of the weight of the polyurethane coating substrate; the corrosion-resistant alloy coating has a thickness of 250 μm and is divided into three equal thicknesses from the inside out, wherein the steel powder accounts for 15%, 25%, and 60% of the total amount of steel powder in the three thicknesses; The steel powder contains 89.4 wt% iron, 5 wt% manganese, 3 wt% chromium, 1.5 wt% silicon, 0.6 wt% phosphorus, 0.3 wt% carbon, and 0.2 wt% boron. The polyurethane coating substrate comprises the following components in parts by weight: 80 parts MDI, 100 parts polyethylene adipate, 30 parts WANNATEHTBL-275MS blocked isocyanate, 15 parts DMAc, and 1.2 parts T12 catalyst. The coating method for the corrosion-resistant alloy coating in this embodiment includes the following steps: 1) Weigh out the steel powder and polyurethane coating base components according to the weight requirements. Mix the polyurethane coating components evenly and divide them into three portions. Add the steel powder to each portion according to the distribution ratio and keep stirring at 10°C. 2) After degassing the mixture from step 1), spray it in order of increasing steel powder content; 3) After the coating is initially solidified with hot air at 70°C, it is then rolled with hot rollers at 150°C. Example

[0017] A corrosion-resistant alloy coating is composed of an epoxy resin coating substrate and steel powder. The amount of steel powder is 5% of the weight of the epoxy resin coating substrate. The thickness of the corrosion-resistant alloy coating is 120 μm, and it is divided into three thicknesses from the inside to the outside. The steel powder accounts for 10%, 20% and 70% of the total amount of steel powder in the three thicknesses. The steel powder contains 82.4 wt% iron, 8 wt% manganese, 5 wt% chromium, 3 wt% silicon, 0.8 wt% phosphorus, 0.5 wt% carbon, and 0.3 wt% boron. The epoxy resin coating substrate comprises the following components in parts by weight: 60 parts of bisphenol F type epoxy resin, 25 parts of p-phenylenediamine curing agent, 15 parts of MR-310 blocked isocyanate, 10 parts of BYK-2013 dispersant, and 1.5 parts of NS-90 non-silicone defoamer. The coating method for the corrosion-resistant alloy coating in this embodiment includes the following steps: 1) Weigh out the steel powder and epoxy resin coating base components according to the weight requirements. Mix the epoxy resin coating components evenly and divide them into three portions. Add the steel powder to each portion according to the distribution ratio and keep stirring at 10°C. 2) After degassing the mixture from step 1), spray it in order of increasing steel powder content; 3) After the coating is initially solidified with hot air at 50°C, it is then rolled with hot rollers at 150°C. Example

[0018] A corrosion-resistant alloy coating is composed of an epoxy resin coating substrate and steel powder, wherein the amount of steel powder is 20% of the weight of the epoxy resin coating; the corrosion-resistant alloy coating has a thickness of 300 μm and is divided into three equal thicknesses from the inside out, wherein the steel powder accounts for 20%, 30%, and 50% of the total amount of steel powder in the three thicknesses; The steel powder contains 95.7 wt% iron, 2 wt% manganese, 1 wt% chromium, 0.5 wt% silicon, 0.5 wt% phosphorus, 0.2 wt% carbon, and 0.1 wt% boron. The epoxy resin coating substrate comprises the following substances in parts by weight: 50 parts of bisphenol A type epoxy resin, 20 parts of p-phenylenediamine curing agent, 20 parts of Desmodur BL3370 blocked isocyanate, 15 parts of DMSO, 5 parts of BYK161 dispersant, and 0.3 parts of organosilicone complex defoamer; The coating method for the corrosion-resistant alloy coating in this embodiment includes the following steps: 1) Weigh out the steel powder and epoxy resin coating base components according to the weight requirements. Mix the epoxy resin coating components evenly and divide them into three portions. Add the steel powder to each portion according to the distribution ratio and keep stirring at 10°C. 2) After degassing the mixture from step 1), spray it in order of increasing steel powder content; 3) After the coating is initially solidified with hot air at 80°C, it is then rolled with hot rollers at 120°C.

[0019] The corrosion-resistant coatings of Comparative Examples 1 to 3 were prepared by using the raw materials of the corrosion-resistant alloy coatings of Examples 1 to 3, mixing them evenly, spraying them to the corresponding thickness, and then curing them with hot air at 50°C to 80°C.

[0020] Table 1 shows the index test results of the corrosion-resistant alloy coatings of Examples 1-3 and the corrosion-resistant coatings of Comparative Examples 1-3. As can be seen from the data in Table 1, the corrosion-resistant alloy coatings of Examples 1-3 are superior to the corrosion-resistant coatings of Comparative Examples 1-3 in all indexes. Regarding corrosion resistance, the coatings of the Examples can resist the erosion of corrosive media for a longer period, and the surface corrosion is significantly less than that of the Comparative Examples. This is because of the unique coating gradient structure of this invention; the higher steel powder content in the outer layer enhances the coating's corrosion resistance, while the lower steel powder content in the inner layer ensures good adhesion to the metal surface, allowing the entire coating to better perform its anti-corrosion function.

[0021] In terms of mechanical properties, the coating in the embodiment also performs better. The hardness, toughness and impact resistance of the coating are significantly improved, and it can better adapt to the effects of temperature changes and mechanical vibrations in harsh environments such as power plants. The hot roll pressing process further compacts the coating, reduces porosity and defects, and improves the density and integrity of the coating, thereby enhancing its mechanical properties.

[0022] In the adhesion test, the coating of the embodiment showed stronger adhesion to the metal surface and was less prone to peeling. This was due to the layered coating method and the treatment method of first setting at low temperature and then curing at high temperature, which eliminated the differences between multiple sprayed layers and made the coating form a continuous and uniform whole.

[0023] Table 1. Test results of corrosion-resistant alloy coatings in Examples 1-3 detection indicators Implementation Standards Example 1 Comparative Example 1 Example 2 Comparative Example 2 Example 3 Comparative Example 3 Adhesion / MPa ISO 4624:2023 14.7 12.3 15.2 13.7 14.8 11.5 abrasion resistance JC / T 1015 0.17 0.18 0.14 0.15 0.11 0.13 Salt spray resistance / h GB / T1771~2007 5000 4000 5000 4000 6000 5000 Non-volatile matter / % GB / T 1725-2007 82 81 92 91 86 84 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A corrosion-resistant alloy coating, characterized in that, The corrosion-resistant alloy coating is composed of a coating substrate and steel powder. The amount of steel powder is 5% to 20% of the weight of the coating substrate. The coating thickness is 120 to 300 μm. The coating is divided into three thicknesses from the inside out. The steel powder accounts for 10% to 20%, 20% to 30%, and 50% to 70% of the total amount of steel powder in the three thicknesses.

2. The corrosion-resistant alloy coating according to claim 1, characterized in that, The steel powder contains 70wt%~95wt% iron, 2wt%~8wt% manganese, 1wt%~5wt% chromium, 0.5wt%~3wt% silicon, 0.5wt%~0.8wt% phosphorus, 0.2wt%~0.5wt% carbon, and 0.1wt%~0.3wt% boron.

3. The corrosion-resistant alloy coating according to claim 2, characterized in that, The coating substrate is a polyurethane coating or an epoxy resin coating.

4. The corrosion-resistant alloy coating according to claim 3, characterized in that, The polyurethane coating comprises the following components in parts by weight: 60-100 parts of diisocyanate, 70-120 parts of polyol, 20-40 parts of blocked isocyanate, 10-20 parts of organic solvent a, and 0.5-2 parts of catalyst.

5. The corrosion-resistant alloy coating according to claim 4, characterized in that, The diisocyanate is one of HDI, MDI, IPDI, TDI or ADI; the polyol is a polyester polyol or a polyether polyol; and the catalyst is an organotin catalyst or an organobismuth catalyst.

6. The corrosion-resistant alloy coating according to claim 3, characterized in that, The epoxy resin coating comprises the following components in parts by weight: 50-70 parts epoxy resin, 15-30 parts curing agent, 10-20 parts blocked isocyanate, 0-20 parts organic solvent b, 5-10 parts dispersant, and 0.1-2 parts defoamer.

7. The corrosion-resistant alloy coating according to claim 6, characterized in that, The curing agent is one or a combination of ethylenediamine, p-phenylenediamine, DETDA, or MDTDA; the dispersant is a BYK dispersant or a polyamide dispersant; and the defoamer is an organosilicone complex or a non-silicone defoamer.

8. The corrosion-resistant alloy coating according to any one of claims 1 to 7, characterized in that, The organic solvent a and organic solvent b are independently selected from one or more combinations of toluene, butyl acetate, butanol, isopropanol, DMAc, EDGA, DMSO, and PGMEA.

9. A method for applying the corrosion-resistant alloy coating as described in claim 8, characterized in that, Includes the following steps: 1) Weigh out the steel powder and coating substrate components according to the weight requirements. Mix the coating substrate components evenly and divide them into three portions. Add the steel powder to each portion according to the distribution ratio and keep stirring at low temperature. 2) After degassing the mixture from step 1), spray it in order of increasing steel powder content; 3) After the coating is initially solidified with hot air at 50℃~80℃, it is then rolled with hot rollers at 120℃~150℃.