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Abstract: Low surface treatment coatings require low surface treatment of the substrate and can save a large amount of surface treatment costs. The principle, characteristics, types and research status of low-surface-treatment coatings were introduced. The prospects for the development of low-surface-treatment coatings and the current domestic problems were analyzed. It is believed that low-surface-treatment coatings that are economical, highly efficient, and environmentally friendly will be studied in the future in China. Hot spot.
Keywords: low surface treatment; rust-borne coatings; wet coating; multi-functional low-surface coatings. 1 INTRODUCTION In order to prevent steel corrosion, many anti-corrosion methods have been developed in scientific experiments and production practices. Among them, the application of anti-corrosion technology with paints is more economical and convenient, so it has been widely used. Before the steel structure is subjected to anti-corrosion coating, in order to ensure the quality of the anti-corrosion coating, steel must be thoroughly blasted. This puts forward high requirements for the entire project construction: 1) sandblasting requires special equipment, consumes a lot of abrasives, increases the project cost, and usually accounts for 30 to 40% of the entire project; 2) for complex work surfaces Structure dead angle can not be completely dealt with; 3) will cause strong dust and noise pollution; 4) sandblasting will cause thinning of the steel structure, so that its strength is reduced, especially in the anticorrosive maintenance of old steel structures, this needs to be pay attention.
On the other hand, in recent years, a large number of offshore oil production platforms, built bridges, electric towers, gymnasiums and other steel structures have entered the maintenance phase at home and abroad, and the old coatings need to be recoated. It is very difficult to carry out sandblast pretreatment on the basis of these constructed steel structures. It involves various aspects such as environmental protection, construction difficulty, and engineering maintenance cost. Therefore, these old steel structures are surface treated with manual derusting at home and abroad. In addition, in the field of shipbuilding and maintenance, as the requirements of workers in various countries around the world are increasingly demanding, high-pressure water rust removal and wet blasting are gradually replacing traditional sandblasting processes, especially for enclosed ships. The steel surface is pre-treated.
The surface of the steel after manual rust removal, high pressure water rust removal, and wet blasting rust removal process is difficult to meet Sa2 grade requirements. Treated steel surfaces often have rust, water, and even oil. For this reason, the development of low surface treatment coatings for surface treatment of pre-painted steel structures (Surface Tolerant Coatings), especially high-performance, high-viscosity long-lasting anti-corrosion low-surface coating and water-based low-surface coating, is currently The research and development hot spot of coatings is also the development trend of coatings in the future.
2 The basic principle of low surface treatment coating technology Rust is a loose porous aqueous solids, the outer layer is floating rust, and the substrate is not firmly attached; the inner layer is a solid rust, and the substrate is closely integrated. From a compositional point of view, it is a mixture of stable and harmless iron oxides (Fe3O4, Fe2O3, alpha-FeOOH) and active detrimental iron compounds (gamma-FeOOH, Fe(OH)2, FeO, Fe(OH)3). Therefore, low surface treatment coatings must have two special conditions in addition to the general anti-rust coating properties. First, the low surface treatment coatings must have sufficient penetration ability for the rust layer, ie, they can fully infiltrate and penetrate the entire surface. Loose porous rust layer, so that rust bonding into a continuous closed coating to seal the entire rust layer and the steel surface; Second, the low surface treatment coating must have sufficient reactivity to the rust layer, which can make the rust layer lively The harmful iron compounds passivate and transform into stable and harmless fillers. Only with these two conditions can we adapt to a special surface such as a rust layer.
Based on the above reasons, the basic principle of low surface treatment coatings is to use a resin with good permeability as the base material, with the help of penetrating agent and polar solvent, so that the coating has good permeability, so as to infiltrate and penetrate the rust layer, and Close it. In addition, depending on the reaction groups of the resin in the coating, reactive pigments or rust transforming agents react with active and harmful components in the rust layer to form a stable inhibiting compound, thereby making the entire rust layer a stable protective film.
3 Basic types of low surface treatment coating technology The development of traditional high-VOC solvent-based low surface treatment coatings (commonly known as “rust-coated coatingsâ€) was developed earlier. As early as the 1970s, a series of such technologies were developed at home and abroad. coating. To sum up can be divided into four categories: permeability type, stable type, conversion type, and functional low surface treatment coatings that have emerged in recent years.
3.1 Conversion Low surface treatment coatings are also called reactive rust coatings. In this type of coating, no film-forming substance is called a rust conversion agent. Since there is no film-forming substance, it is necessary to additionally add a primer; if it contains a film-forming substance, it is called a rust conversion primer. The rusting conversion agent is not a paint, but is used to protect the primer on the rust layer after it is inactive.
The rust conversion primer, because it contains a film-forming substance, can not only transform rust into inert material, but also seal off rust from the outside world. It is a kind of coating that makes the rust layer a solid inert and can adhere well to the steel surface. The main mechanism of this type of coating is to rely on the rust conversion agent in the coating to convert the active rust into harmless or protective complexes or complexes to achieve the purpose of rust coating. Transformed rust paints generally use phosphoric acid-tannic acid to convert the rust layer into insoluble and stable iron phosphate and iron tannin, which play a protective role. However, the amount of acid used is difficult to control, such as excess phosphoric acid. It will promote corrosion, and then suffer endless problems. At the same time, the converted rust-inhibited coating contains less film-forming substances and should preferably be used in combination with other primers. That is to say, after coating the transformed rust-inhibited coating, it is coated with other primers, otherwise the effect is extremely poor. Therefore, the use of transformation type rust paint must be careful. Most of the low surface treatment coatings that were developed early in the country belong to this type of coatings. Conversion-type low-surface-treatment coatings cannot usually be used on their own to ensure long-term corrosion protection, and usually also require topcoats.
3.2 Stable Low Surface Treatment Coating The basic principle of the stable low surface treatment coating is mainly to rely on the reactive groups of the resin in the coating, the reactive pigment and the reactive and harmful components in the rust layer to generate a stable inhibitory compound, thus making the entire rust The layer becomes a stable, protective protective filler component in the coating. Typical stable rust paints use chromate, phosphate and other active mixed pigments that hydrolyze to produce the corresponding chromates and phosphates, forming heteropoly acids. This heteropoly acid forms a complex of heteropolyacids with FeOOH, an active rust in the rust layer, thereby stabilizing the rust. The use of more reactive pigments include: zinc chromate, strontium chromate, calcium chromate, zinc oxide, zinc phosphate, aluminum tripolyphosphate, organic nitrogen alkali chromate, and some formulations also add sodium nitrite, also has information that It is necessary to add barium chromate. The chromate pigments are hydrolyzed to form an anion, and the organic nitrogen base chromate can be hydrolyzed to generate a nitrogen base ion group. Both are absorbed by the active iron rust. Zinc oxide adjusts the pH, and the strontium and calcium ions combine with the acid radicals generated by the sulfur dioxide in the environment as insoluble salts. These combined effects stabilize the rust.
3.3 Permeable Low Surface Treatment Coatings The basic principle of low-surface-treatment coatings is the use of highly permeable resins as the binder. With the aid of penetrating agents and polar solvents, the coating has good permeability and can therefore be impregnated with water. Infiltrate the steel surface rust layer and close the rust layer. It can effectively isolate the corrosion and external corrosion factors, and enhance the adhesion between the corrosion layer and the steel plate, the rust layer and the coating, and the coating and the steel plate.
3.4 Functional low-surface-treatment coatings In recent years, the new low-surface-treatment coatings developed combine the characteristics of conversion, stabilization, and penetration. At the same time, the structure of the resin has been further improved. The base material contains residual energy in the rust layer. The water reacts with the resin, effectively removing and utilizing the corrosive factors. If ketimine is used as a latent curing agent, the paint can penetrate more and increase the depth of entering the rust layer. Simultaneously, the ketimine can react with moisture existing in the rust layer quickly and decompose into a ketone which is the true solvent of the epoxy resin. And primary amine as a curing agent. The primary amine is then reacted with the epoxy resin sufficiently so that the epoxy resin penetrates well into the rust layer, forming a highly cross-linked coating film having a strong covering ability against the external corrosive medium, and fixing the rust layer, and The ketones generated in the curing reaction of the epoxy resin evaporate together with the organic solvent and the moisture in the rust layer, and no bubbles are generated, thereby exhibiting excellent corrosion resistance.
Some functional low surface treatment coatings have the function of oil painting. Because the oil molecules are basically alkane organics, their chemical properties are relatively stable, and they are difficult to remove at room temperature due to chemical reactions. Therefore, they can only be treated by the principle of “similar dissolutionâ€, that is, the use of complex emulsification with oil energy. The base material and additive, curing agent are stripped from the steel plate and mixed as a plasticizer in the coating. Volatile solvents with good compatibility with oil molecules can also take away a portion of the oil molecules during the volatilization process. Commonly used materials include OP series surfactants, sulfonate and sulfate surfactants, ZH-1, CD32 oil-soluble epoxy curing agents, and cashew nut shell oil-modified epoxy curing agents.
Abstract: Low surface treatment coatings require low surface treatment of the substrate and can save a large amount of surface treatment costs. The principle, characteristics, types and research status of low-surface-treatment coatings were introduced. The prospects for the development of low-surface-treatment coatings and the current domestic problems were analyzed. It is believed that low-surface-treatment coatings that are economical, highly efficient, and environmentally friendly will be studied in the future in China. Hot spot.
Keywords: low surface treatment; rust-borne coatings; wet coating; multi-functional low-surface coatings. 1 INTRODUCTION In order to prevent steel corrosion, many anti-corrosion methods have been developed in scientific experiments and production practices. Among them, the application of anti-corrosion technology with paints is more economical and convenient, so it has been widely used. Before the steel structure is subjected to anti-corrosion coating, in order to ensure the quality of the anti-corrosion coating, steel must be thoroughly blasted. This puts forward high requirements for the entire project construction: 1) sandblasting requires special equipment, consumes a lot of abrasives, increases the project cost, and usually accounts for 30 to 40% of the entire project; 2) for complex work surfaces Structure dead angle can not be completely dealt with; 3) will cause strong dust and noise pollution; 4) sandblasting will cause thinning of the steel structure, so that its strength is reduced, especially in the anticorrosive maintenance of old steel structures, this needs to be pay attention.
On the other hand, in recent years, a large number of offshore oil production platforms, built bridges, electric towers, gymnasiums and other steel structures have entered the maintenance period at home and abroad, and the old coatings need to be recoated. It is very difficult to carry out sandblast pretreatment on the basis of these constructed steel structures. It involves various aspects such as environmental protection, construction difficulty, and engineering maintenance cost. Therefore, these old steel structures are surface treated with manual derusting at home and abroad. In addition, in the field of shipbuilding and maintenance, as the requirements of workers in various countries around the world are increasingly demanding, high-pressure water rust removal and wet blasting are gradually replacing traditional sandblasting processes, especially for enclosed ships. The steel surface is pre-treated.
The surface of the steel after manual rust removal, high pressure water rust removal and wet blasting rust removal process is difficult to meet Sa2 grade requirements. Treated steel surfaces often have rust, water and even oil. For this reason, the development of low surface treatment coatings for surface treatment of pre-painted steel structures (Surface Tolerant Coatings), especially high-performance, high-viscosity long-lasting anti-corrosion low-surface treatment coatings and water-based low-surface coating coatings, is currently The research and development of paint is a hotspot, and it is also the development trend of coatings in the future.
2 The basic principle of low surface treatment coating technology Rust is a loose porous aqueous solids, the outer layer is floating rust, and the substrate is not firmly attached; the inner layer is a solid rust, and the substrate is closely integrated. From a compositional point of view, it is a mixture of stable and harmless iron oxides (Fe3O4, Fe2O3, alpha-FeOOH) and active detrimental iron compounds (gamma-FeOOH, Fe(OH)2, FeO, Fe(OH)3). Therefore, low surface treatment coatings must have two special conditions in addition to the general anti-rust coating properties. First, the low surface treatment coatings must have sufficient penetration ability for the rust layer, ie, they can fully infiltrate and penetrate the entire surface. Loose porous rust layer, so that rust bonding into a continuous closed coating to seal the entire rust layer and the steel surface; Second, the low surface treatment coating must have sufficient reactivity to the rust layer, which can make the rust layer lively The harmful iron compounds passivate and transform into stable and harmless fillers. Only with these two conditions can we adapt to a special surface such as a rust layer.
Based on the above reasons, the basic principle of low surface treatment coatings is to use a resin with good permeability as the base material, with the help of penetrating agents and polar solvents, so that the coating has good permeability, so as to infiltrate and penetrate the rust layer, and Close it. In addition, depending on the reaction groups of the resin in the coating, reactive pigments or rust transforming agents react with active and harmful components in the rust layer to form a stable inhibiting compound, thereby making the entire rust layer a stable protective film.
3 Basic types of low surface treatment coating technology The development of traditional high-VOC solvent-based low surface treatment coatings (commonly known as “rust-coated coatingsâ€) was developed earlier. As early as the 1970s, a series of such technologies were developed at home and abroad. coating. To sum up can be divided into four categories: permeability type, stable type, conversion type, and functional low surface treatment coatings that have emerged in recent years.
3.1 Conversion Low surface treatment coatings are also called reactive rust coatings. In this type of coating, no film-forming substance is called a rust conversion agent. Since there is no film-forming substance, it is necessary to additionally add a primer; if it contains a film-forming substance, it is called a rust conversion primer. The rusting conversion agent is not a paint, but is used to protect the primer on the rust layer after it is inactive.
The rust conversion primer, because it contains a film-forming substance, can not only transform rust into an inert substance, but also seal off rust from the outside. It is a kind of coating that makes the rust layer a solid inert and can be well attached to the steel surface. The main mechanism of this type of coating is to rely on the rust conversion agent in the coating to convert the active rust into harmless or protective complexes or complexes to achieve the purpose of rust coating. Transformed rust paints generally use phosphoric acid-tannic acid to convert the rust layer into insoluble and stable iron phosphate and iron tannin, which play a protective role. However, the amount of acid used is difficult to control, such as excess phosphoric acid. It will promote corrosion, and then suffer endless problems. At the same time, the conversion type rust-free paint contains less film-forming substances, and it is better to use it in combination with other primers. That is, after painting the conversion type rust-inhibited paint, it is coated with other primers, otherwise the effect is extremely poor. Therefore, the use of transformation type rust paint must be careful. Most of the low surface treatment coatings that were developed early in the country belong to this type of coatings. Conversion-type low-surface-treatment coatings cannot usually be used on their own to ensure long-term corrosion protection, and usually also require topcoats.
3.2 Stable Low Surface Treatment Coating The basic principle of the stable low surface treatment coating is mainly to rely on the reactive groups of the resin in the coating, the reactive pigment and the reactive and harmful components in the rust layer to generate a stable inhibitory compound, thus making the entire rust The layer becomes a stable, protective protective filler component in the coating. Typical stable rust paints use chromate, phosphate and other active mixed pigments that hydrolyze to produce the corresponding chromates and phosphates, forming heteropoly acids. This heteropoly acid forms a complex of heteropolyacids with FeOOH, an active rust in the rust layer, thereby stabilizing the rust. The use of more reactive pigments include: zinc chromate, strontium chromate, calcium chromate, zinc oxide, zinc phosphate, aluminum tripolyphosphate, organic nitrogen alkali chromate, and some formulations also add sodium nitrite, also has information that It is necessary to add barium chromate. The chromate pigments are hydrolyzed to form an anion, and the organic nitrogen base chromate can be hydrolyzed to generate a nitrogen base ion group. Both are absorbed by the active iron rust. Zinc oxide adjusts the pH, and the strontium and calcium ions combine with the acid radicals generated by the sulfur dioxide in the environment as insoluble salts. These combined effects stabilize the rust.
3.3 Permeable Low Surface Treatment Coatings The basic principle of the low permeability surface treatment coatings is the use of highly permeable resins as the binder. With the aid of penetrating agents and polar solvents, the coating has good permeability and can therefore be impregnated with Infiltrate the steel surface rust layer and close the rust layer. It can effectively isolate the corrosion and external corrosion factors, and enhance the adhesion between the corrosion layer and the steel plate, the rust layer and the coating, and the coating and the steel plate.
3.4 Functional low-surface-treatment coatings In recent years, the new low-surface-treatment coatings developed combine the characteristics of conversion, stabilization, and penetration. At the same time, the structure of the resin has been further improved. The base material contains residual energy in the rust layer. The water reacts with the resin, effectively removing and utilizing the corrosive factors. If ketimine is used as a latent curing agent, the paint can penetrate more and increase the depth of entering the rust layer. Simultaneously, the ketimine can react with the water present in the rust layer and decompose to a ketone which is the true solvent of the epoxy resin. And primary amine as a curing agent. The primary amine is then reacted with the epoxy resin sufficiently so that the epoxy resin penetrates well into the rust layer, forming a highly cross-linked coating film having a strong covering ability against the external corrosive medium, and fixing the rust layer, and The ketones generated in the curing reaction of the epoxy resin evaporate together with the organic solvent and the moisture in the rust layer, and no bubbles are generated, thereby exhibiting excellent corrosion resistance.
Some functional low surface treatment coatings have the function of oil painting. Because the oil molecules are basically alkane organics, their chemical properties are relatively stable, and they are difficult to remove at room temperature due to chemical reactions. Therefore, they can only be treated by the principle of “similar dissolutionâ€, that is, the use of complex emulsification with oil energy. The base material and additive, curing agent are stripped from the steel plate and mixed as a plasticizer in the coating. Volatile solvents with good compatibility with oil molecules can also take away a portion of the oil molecules during the volatilization process. Commonly used materials include OP series surfactants, sulfonate and sulfate surfactants, ZH-1, CD32 oil-soluble epoxy curing agents, and cashew nut shell oil-modified epoxy curing agents.
Abstract: Low surface treatment coatings require low surface treatment of the substrate and can save a large amount of surface treatment costs. The principle, characteristics, types and research status of low-surface-treatment coatings were introduced. The prospects for the development of low-surface-treatment coatings and the current domestic problems were analyzed. It is believed that low-surface-treatment coatings that are economical, highly efficient, and environmentally friendly will be studied in the future in China. Hot spot.
Keywords: low surface treatment; rust-borne coatings; wet coating; multi-functional low-surface coatings. 1 INTRODUCTION In order to prevent steel corrosion, many anti-corrosion methods have been developed in scientific experiments and production practices. Among them, the application of anti-corrosion technology with paints is more economical and convenient, so it has been widely used. Before the steel structure is subjected to anti-corrosion coating, in order to ensure the quality of the anti-corrosion coating, steel must be thoroughly blasted. This puts forward high requirements for the entire project construction: 1) sandblasting requires special equipment, consumes a lot of abrasives, raises the project cost, and usually accounts for 30 to 40% of the entire project; 2) for complex work surfaces Structure dead angle can not be completely dealt with; 3) will cause strong dust and noise pollution; 4) sandblasting will cause thinning of the steel structure, so that its strength is reduced, especially in the anticorrosive maintenance of old steel structures, this needs to be pay attention.
On the other hand, in recent years, a large number of offshore oil production platforms, built bridges, electric towers, gymnasiums and other steel structures have entered the maintenance period at home and abroad, and the old coatings need to be recoated. It is very difficult to carry out sandblast pretreatment on the basis of these constructed steel structures. It involves various aspects such as environmental protection, construction difficulty, and engineering maintenance cost. Therefore, these old steel structures are surface treated with manual derusting at home and abroad. In addition, in the field of shipbuilding and maintenance, as the requirements of workers in various countries around the world are increasingly demanding, high-pressure water rust removal and wet blasting are gradually replacing traditional sandblasting processes, especially for enclosed ships. The steel surface is pre-treated.
The surface of the steel after manual rust removal, high pressure water rust removal and wet blasting rust removal process is difficult to meet Sa2 grade requirements. Treated steel surfaces often have rust, water and even oil. For this reason, the development of low surface treatment coatings for surface treatment of pre-painted steel structures (Surface Tolerant Coatings), especially high-performance, high-viscosity long-lasting anti-corrosion low-surface treatment coatings and water-based low-surface coating coatings, is currently The research and development hot spot of coatings is also the development trend of coatings in the future.
2 The basic principle of low surface treatment coating technology Rust is a loose porous aqueous solids, the outer layer is floating rust, and the substrate is not firmly attached; the inner layer is a solid rust, and the substrate is closely integrated. From a compositional point of view, it is a mixture of stable and harmless iron oxides (Fe3O4, Fe2O3, alpha-FeOOH) and active detrimental iron compounds (gamma-FeOOH, Fe(OH)2, FeO, Fe(OH)3). Therefore, low surface treatment coatings must have two special conditions in addition to the general anti-rust coating properties. First, the low surface treatment coatings must have sufficient penetration ability for the rust layer, ie, they can fully infiltrate and penetrate the entire surface. Loose porous rust layer, so that rust bonding into a continuous closed coating to seal the entire rust layer and the steel surface; Second, the low surface treatment coating must have sufficient reactivity to the rust layer, which can make the rust layer lively The harmful iron compounds passivate and transform into stable and harmless fillers. Only with these two conditions can we adapt to a special surface such as a rust layer.
Based on the above reasons, the basic principle of low surface treatment coatings is to use a resin with good permeability as the base material, with the help of penetrating agents and polar solvents, so that the coating has good permeability, so as to infiltrate and penetrate the rust layer, and Close it. In addition, depending on the reaction groups of the resin in the coating, reactive pigments or rust transforming agents react with active and harmful components in the rust layer to form a stable inhibiting compound, thereby making the entire rust layer a stable protective film.
3 Basic types of low surface treatment coating technology The development of traditional high-VOC solvent-based low surface treatment coatings (commonly known as “rust-coated coatingsâ€) was developed earlier. As early as the 1970s, a series of such technologies were developed at home and abroad. coating. To sum up can be divided into four categories: permeability type, stable type, conversion type, and functional low surface treatment coatings that have emerged in recent years.
3.1 Conversion Low surface treatment coatings are also called reactive rust coatings. In this type of coating, no film-forming substance is called a rust conversion agent. Since there is no film-forming substance, it is necessary to additionally add a primer; if it contains a film-forming substance, it is called a rust conversion primer. The rusting conversion agent is not a paint, but is used to protect the primer on the rust layer after it is inactive.
The rust conversion primer, because it contains a film-forming substance, can not only transform rust into inert material, but also seal off rust from the outside world. It is a kind of coating that makes the rust layer a solid inert and can adhere well to the steel surface. The main mechanism of this type of coating is to rely on the rust conversion agent in the coating to convert the active rust into harmless or protective complexes or complexes to achieve the purpose of rust coating. Transformed rust paints generally use phosphoric acid-tannic acid to convert the rust layer into insoluble and stable iron phosphate and iron tannin, which play a protective role. However, the amount of acid used is difficult to control, such as excess phosphoric acid. It will promote corrosion, and then suffer endless problems. At the same time, the conversion type rust-free paint contains less film-forming substances, and it is better to use it in combination with other primers. That is, after painting the conversion type rust-inhibited paint, it is coated with other primers, otherwise the effect is extremely poor. Therefore, the use of transformation type rust paint must be careful. Most of the low surface treatment coatings that were developed early in the country belong to this type of coatings. Conversion-type low-surface-treatment coatings cannot usually be used on their own to ensure long-term corrosion protection, and usually also require topcoats.
3.2 Stable Low Surface Treatment Coating The basic principle of the stable low surface treatment coating is mainly to rely on the reactive groups of the resin in the coating, the reactive pigment and the reactive and harmful components in the rust layer to generate a stable inhibitory compound, thus making the entire rust The layer becomes a stable, protective protective filler component in the coating. Typical stable rust paints use chromate, phosphate and other active mixed pigments that hydrolyze to produce the corresponding chromates and phosphates, forming heteropoly acids. This heteropoly acid forms a complex of heteropoly acids with FeOOH, an active rust in the rust layer, thereby stabilizing the rust. The use of more reactive pigments include: zinc chromate, strontium chromate, calcium chromate, zinc oxide, zinc phosphate, aluminum tripolyphosphate, organic nitrogen alkali chromate, and some formulations also add sodium nitrite, also has information that It is necessary to add barium chromate. The chromate pigments are hydrolyzed to form an anion, and the organic nitrogen base chromate can be hydrolyzed to generate a nitrogen base ion group. Both are absorbed by the active iron rust. Zinc oxide adjusts the pH, and the strontium and calcium ions combine with the acid radicals generated by the sulfur dioxide in the environment as insoluble salts. These combined effects stabilize the rust.
3.3 Permeable Low Surface Treatment Coatings The basic principle of low-surface-treatment coatings is the use of highly permeable resins as the binder. With the aid of penetrating agents and polar solvents, the coating has good permeability and can therefore be impregnated with water. Infiltrate the steel surface rust layer and close the rust layer. It can effectively isolate the corrosion and external corrosion factors, and enhance the adhesion between the corrosion layer and the steel plate, the rust layer and the coating, and the coating and the steel plate.
3.4 Functional low-surface-treatment coatings In recent years, the new low-surface-treatment coatings developed combine the characteristics of conversion, stabilization, and penetration. At the same time, the structure of the resin has been further improved. The base material contains residual energy in the rust layer. The water reacts with the resin, effectively removing and utilizing the corrosive factors. If ketimine is used as a latent curing agent, the paint can penetrate more and increase the depth of entering the rust layer. Simultaneously, the ketimine can react with the water present in the rust layer and decompose to a ketone which is the true solvent of the epoxy resin. And primary amine as a curing agent. The primary amine is then reacted with the epoxy resin sufficiently so that the epoxy resin penetrates well into the rust layer, forming a highly cross-linked coating film having a strong covering ability against the external corrosive medium, and fixing the rust layer, and The ketones generated in the curing reaction of the epoxy resin evaporate together with the organic solvent and the moisture in the rust layer, and no bubbles are generated, thereby exhibiting excellent corrosion resistance.
Some functional low surface treatment coatings have the function of oil painting. Because the oil molecules are basically alkane organics, their chemical properties are relatively stable, and they are difficult to remove at room temperature due to chemical reactions. Therefore, they can only be treated by the principle of “similar dissolutionâ€, that is, the use of complex emulsification with oil energy. The base material and additive, curing agent are stripped from the steel plate and mixed as a plasticizer in the coating. Volatile solvents with good compatibility with oil molecules can also take away a portion of the oil molecules during the volatilization process. Commonly used materials include OP series surfactants, sulfonate and sulfate surfactants, ZH-1, CD32 oil-soluble epoxy curing agents, and cashew nut shell oil-modified epoxy curing agents.
4 Development trend of low surface treatment coating technology Due to the improvement of the living environment requirements and the enhancement of environmental protection awareness, there is an urgent need for low-pollution or pollution-free low-surface-treatment coatings in the society. At the same time, people also have anticorrosive properties for low surface treatment coatings. Put forward higher requirements. under these circumstances. The research and application of high-potency long-term anti-corrosion low-surface-treatment paints and water-based low-surface-treatment paints have been strengthened at home and abroad.
4.1 High-Purity, Long-Surface, Anti-Corrosion, Low-Surface Coatings American Tapecoat's penetrating high-pure epoxy-aluminum powder low-surface-treatment coating is an offshore oil drilling platform with more than 10 years of application performance and over 10,000 square meters of coating practice. The thick paste type long-term anti-corrosion low surface treatment coating. From the perspective of rust prevention mechanism, it belongs to the infiltrating type. This coating uses a modified epoxy resin with good permeability to infiltrate, infiltrate, fill with porous rust layer, replace the moisture of the rust layer, and form a continuous coating film. The rust layer and the steel surface are encapsulated so as to insulate the rust layer from the external corrosive medium and prevent the development of rust. In addition, it also uses flake-type aluminum powder as a filler, which forms a tile-like structure intertwined in the coating, which has excellent shielding and can block the infiltration of corrosive media from the outside. At the same time, it can reflect ultraviolet rays to improve the weather resistance of the epoxy coating.
Other similar coatings include Jotamastic87 produced by JotumProteciveCoating in Norway, Carbomastic15 produced by Carboling in the United States, and Amerlock400 and Amerlock400 low-surface-treatment coatings from Ameron. This kind of paint also changed the surname on the composition structure of the resin, reduced its surface tension, improved the ability to rust the active corrosion, and also added flake pigments to improve the anti-rust performance and anti-foaming ability.
The above-mentioned high-slurry low-surface-treatment paints are suitable for wet blasting or water-washing after blasting to generate a rust-free steel surface, and have excellent adhesion to corroded steel plates and many old paints, requiring only preliminary processing. Can achieve a good comprehensive anti-rust performance, and a lot of old paint has a good compatibility, easy construction, and a coating up to 120 microns.
The Japanese paint company also reported that the company has developed a thick-film long-term anti-corrosion coating with excellent anti-corrosion properties for the corrosion of marine steel structures under harsh corrosive environments. The reason why the coating has good flexibility, thick film, wet surface adhesion and rust surface corrosion resistance is because: 1) The use of a good adhesion with the rust surface of the resin, so that the longitudinal elastic modulus decreased, The internal stress is reduced and no rust layer with weak cohesion is produced. The standard film thickness is 1000 μm, and the adhesion to the rust surface is still good. 2) The use of special hydrophobic resin can remove the water in the rust layer. Wet surface adhesion is also very good; 3) Use special anti-rust pigments, control the film under the cathode, anode reaction, so that the rust layer stability, prevent the development of corrosion.
4.2 Water-based low-surface treatment Long-term anti-corrosion coating Water-based low-surface-treatment coatings mostly use aqueous emulsions or resins such as styrene-acrylic emulsions, pure acrylic emulsions, etc., and are made of active rust-proof pigments such as aluminum triphosphate, zinc phosphate, and zinc oxide. Into coating, this type of coating is also used to penetrate into the rust layer of the coating, and surround the rust. The P3O105- and PO3- in the active pigment are complexed with the polar group (-OH, -COOH) in the film former. In addition to stabilizing cross-linking compounds, they are more capable of forming hydrazine compounds with Fe and Fe, indicating the formation of a stable protective film on the metal, inhibiting the formation and delamination of rust, and thus playing a role in rust prevention.
The RustReformer from Rust-Oleum, a foreign company, is a polymer emulsion containing a rust transforming agent that transforms rust into an inert, non-corrosive, black substance. Haloflex (chlorinated ethylene-acrylic acid interpolymer) is a film-forming substance recommended for use in tannin conversion agents for rust conversion primers due to the conversion of tannic acid and rust at pH 1.5 to 2 acidic conditions. While Haloflex is an acidic emulsion, this acidic emulsion is ideal as a film-forming material for aqueous rust conversion primers.
4.3 Interpenetrating network polymer (IPN) stable low surface treatment coating Liang Chunqun and others from Huazhong University of Science and Technology used castor oil and TDI to synthesize prepolymer with NCO/OH=2.1 mol ratio at room temperature, and then measured with castor oil, 191 unsaturated polyester mixed with vinyl chloride. Then, a small amount of catalyst Sn and redox initiator are added, and an interpenetrating network polymer (IPN) stabilized low surface treatment coating prepared by mixing with active rust-inhibitive pigments such as zinc phosphate, zinc oxide, and iron red has a high quality solids content. 70% for rusted iron plate, soaked in 3.0% saline for 10 months, the coating has no foaming and cracking, and has good anti-corrosion properties. This study lays a foundation for the further use of IPN coatings for low surface treatment coatings.
5 Nomenclature In summary, early-stage low-surface-treatment paints were mostly high-VOC solvent-based paints with a single mechanism of action. Such coatings have a low corrosion life and are not conducive to environmental protection. With the development of science and the progress of society, low surface treatment coatings will develop in the following ways:
a) Develop reactive resins, chelating resins, and other varieties that have good stabilizing effects on corrosion from raw materials;
b) From the principle of action, it should be developed from a single permeation type, a stable type, and a conversion type in the direction of multi-functional coatings combined with multiple principles, so as to greatly improve the performance and effectiveness of low surface treatment coatings;
c) Develop high-performance long-term anti-corrosion and low-surface-treatment coatings from the anti-corrosion effect;
d) From the perspective of environmental protection, towards the direction of energy conservation and improvement of the construction environment, such as the development of high-solids, water-based coatings.
In short, low surface treatment coatings have high practical value and will have a broad market prospect. With the development of science and technology and the needs of production and life, this type of coating will be widely used in various fields.
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作者简介：æ¨æŒ¯æ³¢ï¼ˆ1978—），男，四å·å¹¿å…ƒäººï¼Œç¡•å£«ï¼Œå·¥ç¨‹å¸ˆï¼Œç ”究方å‘为防è…涂料åŠæ¶‚装。
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