Chromium-free anti-corrosion coating compositions and articles made therefrom

Abstract

This invention relates to chromium-free anti-corrosion coating compositions and articles made therefrom. The chromium-free anti-corrosion coating composition comprises: component A, including a film-forming composition, a corrosion-inhibiting composition, optionally a carrier, and additional additives, wherein the corrosion-inhibiting composition comprises: rust-inhibiting particles containing at least one lithium phosphate compound, wherein the rust-inhibiting particles have a lithium content of at least 1.0% by weight; and optionally, component B, including a curing agent. The chromium-free anti-corrosion coating composition of this invention can be used as a primer or a combined primer and topcoat. This invention also discloses an article comprising a metal substrate and a coating formed by the above-described chromium-free anti-corrosion coating composition and applied directly onto the metal substrate.

Description

Chromium-free anti-corrosion coating compositions and articles made therefrom This invention relates to an anti-corrosion coating composition, and more particularly to a chromium-free anti-corrosion coating composition having excellent anti-corrosion properties and articles made therefrom. Metal corrosion is the process by which metallic materials come into contact with their surrounding environment and undergo a reaction, gradually leading to their destruction or deterioration. Metal corrosion is a common natural phenomenon; examples include rust on steel surfaces and white powder on aluminum products. To prevent corrosion, anti-corrosion treatments are applied to the metal substrate. These treatments provide crucial protection for extending the service life of the metal substrate and ensuring safe application. Hexavalent chromium compounds are widely recognized as providing excellent corrosion protection for coatings, effective across a wide range of pH levels and possessing self-healing properties, thus making them almost irreplaceable corrosion-resistant pigments / fillers. However, hexavalent chromium is toxic. Since the 1920s, there has been documented evidence that hexavalent chromium is inherently carcinogenic, and numerous previous studies have shown that direct contact with chromium... 6+ The use of hexavalent chromium compounds in industrial workers has led to a significant increase in the incidence of nasal and lung cancer. Due to environmental, worker safety, and regulatory concerns, there are growing calls to gradually reduce or even eliminate the use of hexavalent chromium compounds in anti-corrosion coatings. Therefore, there has always been a demand for chromium-free anti-corrosion coating compositions in the coatings industry. This invention provides a chromium-free anti-corrosion coating composition comprising: component A, including a film-forming composition, a corrosion-inhibiting composition, optional carrier, and additional additives, wherein the corrosion-inhibiting composition comprises: rust-inhibiting particles containing at least one lithium phosphate compound, wherein the rust-inhibiting particles have a lithium content of at least 1.0% by weight; and optionally, component B, including a curing agent. Preferably, the rust-inhibiting particles have a lithium content of at least 5.0% by weight, more preferably 7.0% by weight or higher. In some embodiments of the invention, the corrosion-inhibiting composition further comprises at least one cation-exchange silicone. The present invention also provides an article comprising a metal substrate and a coating formed by directly applying the coating to the metal substrate using the chromium-free anti-corrosion coating composition of the present invention. Preferably, the metal substrate is selected from one or more of steel, iron, aluminum, zinc, copper, and alloys. The inventors of this invention have surprisingly discovered that in the formulation of chromium-free anti-corrosion coating compositions, the corrosion-inhibiting composition comprising a phosphate compound containing at least one lithium and having rust-inhibiting particles with a lithium content of at least 1.0% by weight, preferably at least 5.0% by weight, more preferably 7.0% by weight or higher, can result in a paint film formed therefrom exhibiting excellent corrosion resistance, for example, being able to remain in a water environment at 40°C for 18 days or longer without bubbling, which was unforeseen before this invention. The inventors of this invention were even more surprised to discover that, in the formulation of the chromium-free anti-corrosion coating composition, the corrosion-inhibiting composition comprising a phosphate compound containing at least one lithium and having at least 1.0% by weight, preferably at least 5.0% by weight, more preferably 7.0% by weight or higher of lithium-containing rust-inhibiting particles and at least one cation-exchange silicone, enables the coating film formed therefrom to not only exhibit excellent water resistance but also excellent salt spray resistance. The water resistance is demonstrated by the fact that the formed coating film does not blister after being stored in a water environment at 40°C for 18 days or longer and in a water environment at room temperature for 500 hours. The salt spray resistance is demonstrated by the fact that the formed coating film, after undergoing a salt spray test according to ASTM B117 or GB / T1771 for 500 hours or longer, has a single-sided peel width not exceeding 2 mm. It is not intended to be bound by any theory, but the reason why the chromium-free anti-corrosion coating composition of the present invention can achieve the above-mentioned anti-corrosion effect is as follows. In the formulation of the anti-corrosion coating composition of the present invention, the corrosion-inhibiting composition comprises a phosphate compound containing at least one lithium and rust-inhibiting particles having a lithium content of at least 1.0% by weight, preferably at least 5.0% by weight, more preferably 7.0% by weight or higher. In a corrosive environment, the lithium phosphate compound contained in the coating formed by the above-described anti-corrosion coating composition can release and / or leachable lithium ions. The dissociated lithium ions act as cathode inhibitors, reacting with oxygen, water, etc., in the environment to form a passivation layer that protects the metal substrate from external corrosion. Over time, the rust-inhibiting particles, due to their significantly higher lithium ion content, can continuously replenish the lithium ions consumed by oxygen, water, etc., in the environment, thus forming an anti-corrosion coating with longer water resistance. For example, in some embodiments of the present invention, the paint film formed by the anti-corrosion coating composition according to the present invention can be stored in a water environment at 40°C for 18 days or longer, even 30 days or longer, or even 50 days without blistering. In the formulation of the anti-corrosion coating composition of the present invention, the corrosion-inhibiting composition may further include cation-exchange silicone. In a corrosive environment, corrosive ions such as (H+) penetrate into the coating film. + ), on the surface of silicone particles, cations (such as calcium ions (Ca) 2+The cation exchange process occurs, releasing corresponding cations that then migrate to the interface of the metal substrate and further form a protective film on the metal substrate interface. Therefore, cation exchange silicone can not only adsorb corrosive ions from the environment but also form a protective film on the interface of the metal substrate. Thus, the cation exchange silicone included in the corrosion-inhibiting composition acts as a reinforcing agent, further enhancing the anti-corrosion effect of rust-inhibiting particles containing at least one lithium phosphate compound. Furthermore, the rust-inhibiting particles containing at least one lithium phosphate compound in the corrosion-inhibiting composition can be derived from lithium phosphate aluminum fillers, offering the advantage of low cost. In other words, coating compositions formulated therefrom maintain excellent anti-corrosion performance while being cost-effective, making them suitable for widespread application. The inventors of this invention were even more surprised to discover that the anti-corrosion coating composition according to the present invention can be used not only as a primer suitable for wet-to-dry systems, but also as a primer suitable for wet-to-wet systems. Moreover, when used as a primer for wet-to-wet systems, the anti-corrosion coating composition according to the present invention not only avoids construction problems such as sagging and streaking, but also achieves excellent anti-corrosion effects. Details of one or more embodiments of the present invention are set forth in the following description. Other features, objects, and advantages of the invention will become clear from the description and claims. definition In this document, the terms “a,” “the,” “at least one,” and “one or more” or no quantifier are used interchangeably. Thus, for example, a component containing “a” additive can be interpreted as meaning that the component contains “one or more” additives. When a composition is described as including or comprising specific components, it is anticipated that optional components not covered by the present invention are not excluded from the composition, and that the composition may be constituted or composed of the components involved. Similarly, when a method is described as including or comprising specific process steps, it is anticipated that optional process steps not covered by the present invention are not excluded from the method, and that the method may be constituted or composed of the process steps involved. For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range. The term "anti-corrosion coating composition" refers to a coating composition that, when applied in one or more layers to a metal substrate, forms a coating that can be exposed to corrosive conditions (e.g., salt spray exposure for three weeks or more) for a considerable period of time without exhibiting unpleasant visible deterioration or corrosion. When used in connection with a “chromium-free anti-corrosion coating composition,” the term “chromium-free” means that none of the components of the coating composition, nor the coating composition formed therefrom, contains any additional hexavalent chromium ions, and preferably none of any chromium-containing compounds. When the phrases “free of,” “does not contain any,” etc., are used herein, such phrases are not intended to exclude the presence of trace amounts of related structures or compounds that may be present as environmental pollutants or due to environmental pollution. As used herein, the term "rust-preventive particles containing at least one lithium phosphate compound" refers to rust-preventive particles that are primarily composed of at least one lithium phosphate compound, but may additionally contain other components and / or elements that may promote / enhance and / or not adversely affect the corrosion-preventive properties of the rust-preventive particles. When referring to the use of "rust-preventive particles," the phrase "having at least 1.0% by weight of lithium content" means the lithium content of the rust-preventive particles as determined by X-ray photoelectron spectroscopy (XPS) elemental analyzer, such as a Thermo XPS elemental analyzer, using the rust-preventive particles as a sample. In some embodiments of the invention, the rust-preventive particles have a lithium content of at least 5.0% by weight, preferably at least 7.0% by weight or higher. As used herein, the term "lithium phosphate compound" refers to a compound comprising a lithium cation and a phosphate anion. Depending on the requirements, such a compound may also be doped with one or more other cations and / or anions. For example, such lithium phosphate compounds may be doped with fluoride ions, hydroxide ions, and / or other anions that do not adversely affect the corrosion-resistant properties of the lithium phosphate compound, and / or aluminum ions, calcium ions, iron ions, magnesium ions, manganese ions, strontium ions, nickel ions, and / or other cations that do not affect the corrosion-resistant properties of the lithium phosphate compound. When used in relation to “lithium phosphate compounds”, the phrase “having releasable and / or leaching lithium ions” means that, under corrosive conditions, such as in a 5% by weight aqueous spray of sodium chloride at a temperature of 35°C or higher, the lithium in the lithium phosphate compound can dissociate into lithium ions. When referring to "lithium phosphate compounds," the phrase "having a spatially stable crystal structure" means that the compound possesses structural stability, its crystal structure facilitating the extraction and insertion (or deintercalation) of lithium ions and other cations, and that the crystal structure remains essentially stable during the extraction and insertion of lithium ions and other cations, without significant lattice changes. Coatings formed from paint compositions containing this lithium phosphate compound, under certain conditions, particularly corrosive conditions (e.g., 600 hours or longer at 35°C in a 5% sodium chloride aqueous spray), maintain a spatially stable three-dimensional structure after the dissociation of lithium ions and / or other cations. The coating does not exhibit collapse, porosity, or other phenomena. The "collapse" or "porosity" phenomena on the coating surface are measured using a scanning electron microscope (SEM). The "spatially stable crystal structure," as an example, can be a triclinic crystal structure. As used herein, the term "cation-exchangeable silica" refers to amorphous silica on which cations are adsorbed or attached, which can be exchanged with specific cations (e.g., hydrogen ions). When used in relation to "chromium-free anti-corrosion coating compositions," the term "film-forming composition" refers to a component that, after being mixed with other components in the coating composition (e.g., carriers, additives, fillers, etc.) and applied to a substrate, is dried, cross-linked, or otherwise cured as needed with a suitable curing agent, thereby forming a non-sticky, continuous film on the substrate. The "film-forming composition" primarily comprises a resin component and may also contain inorganic silicate film-forming substances. When used herein, the term "primer" refers to a coating composition that can be applied to a metal substrate and dried, crosslinked, or otherwise hardened to form a non-sticky, continuous film with adequate adhesion to the substrate surface. When used herein, the term "Direct-To-Metal (DTM) coating" refers to a coating composition that can be applied to a metallic substrate and dried, crosslinked, or otherwise hardened to form a non-sticky, continuous film with good adhesion to the substrate surface, and which can withstand long-term outdoor exposure without showing visible unsatisfactory degradation. A Direct-To-Metal (DTM) coating functions as both a primer (e.g., providing strong adhesion and corrosion resistance) and a topcoat (e.g., exhibiting good appearance and decorative effects). Compared to applying primer and topcoat separately, a Direct-To-Metal (DTM) coating reduces application costs and time. When used herein, the term "wet-on-wet system" refers to a coating system formed by a "wet-on-wet process," where a second coat of paint is applied before the first coat has fully dried. In some embodiments of the invention, the anti-corrosion coating composition according to the invention can be used as a primer suitable for wet-on-wet systems, not only avoiding application problems such as sagging and wrinkling, but also achieving excellent anti-corrosion performance. When used herein, the term "wet-to-dry system" refers to a coating system formed by a "wet-to-dry process," where a second coat of paint is applied after the first coat has fully dried. In the coatings industry, the wet-to-dry process is the most commonly used technique for applying multiple layers of coatings and is suitable for the vast majority of coatings. When used in this specification and requests, the terms “comprising” and “including” and their variations are not restrictive. The terms "preferred" and "ideally" refer to embodiments of the invention that provide certain benefits in certain circumstances. However, other embodiments may also be preferred in the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor does it exclude other embodiments from the scope of the invention. Figure 1 shows a photograph of a composite coating formed by coating a primer layer of an epoxy resin-based chromium-free anti-corrosion coating composition according to Examples 1-3 of the present invention with a water-based polyurethane topcoat after immersion in a water environment at 40°C for 18 days. The coating above the black line is not immersed in water, while the coating below the black line is immersed in water. Figure 2 shows a photograph of a composite coating formed by coating a primer layer of an epoxy resin-based chromium-free anti-corrosion coating composition according to Examples 1-3 of the present invention with a water-based polyurethane topcoat, after being immersed in water at room temperature for 500 hours. The coating above the black line is not immersed in water, while the coating below the black line is immersed in water. Figure 3 shows a photograph of a composite coating formed by coating a primer layer of the epoxy resin-based chromium-free anti-corrosion coating composition according to Examples 4-6 of the present invention with a water-based polyurethane topcoat after immersion in a water environment at 40°C for 18 days. The coating above the black line is not immersed in water, while the coating below the black line is immersed in water. Figure 4 shows a photograph of a composite coating formed by coating a primer layer of an epoxy resin-based chromium-free anti-corrosion coating composition according to Examples 4-6 of the present invention with a water-based polyurethane topcoat, after being immersed in water at room temperature for 500 hours. The coating above the black line is not immersed in water, while the coating below the black line is immersed in water. Figure 5 shows photographs of composite coatings formed by applying a water-based polyurethane topcoat to a primer layer of the epoxy resin-based chromium-free anti-corrosion coating composition according to Examples 4-6 of the present invention after undergoing ASTM B117 salt spray resistance tests for 502 hours (top coat) and 790 hours (bottom coat). This invention provides a chromium-free anti-corrosion coating composition comprising: component A, including a film-forming composition, a corrosion-inhibiting composition, an optional carrier, and additional additives, wherein the corrosion-inhibiting composition comprises: rust-inhibiting particles containing at least one lithium phosphate compound, wherein the rust-inhibiting particles have a lithium content of at least 1.0% by weight; and optionally, component B, including a curing agent. Preferably, the anti-corrosion inhibiting composition further comprises a cation-exchange silicone. As discussed in the previous technical section, there is a growing call to gradually reduce or even eliminate the use of hexavalent chromium compounds in anti-corrosion coatings. In light of this, scientists in the coatings industry have conducted extensive research in recent years to find alternative anti-corrosion pigments / fillers to replace hexavalent chromium compounds. Although many alternative agents have been proposed, none have shown acceptable anti-corrosion performance in anti-corrosion coating applications. The primary objective in selecting anti-corrosion pigments / fillers is to ensure that the coatings formulated with them meet corrosion resistance standards based on ASTM B117 or even GB / T 1771 salt spray tests (these are recognized methods in the aerospace industry), and ideally, also meet water resistance tests. In practice, coatings formulated with conventional chromium-free anti-corrosion pigments / fillers, such as aluminum tripolyphosphate, do not meet the aforementioned corrosion resistance standards, let alone the aforementioned water resistance tests. As described above, the inventors of this invention have surprisingly discovered that in the formulation of chromium-free anti-corrosion coating compositions, the corrosion-inhibiting composition comprising phosphate compounds containing at least one lithium and having rust-inhibiting particles with a lithium content of at least 1.0% by weight, preferably at least 5.0% by weight, more preferably 7.0% by weight or higher, can make the coating film formed therefrom exhibit acceptable corrosion resistance and excellent water resistance, wherein the water resistance is manifested in that the formed coating film does not blister when stored in a water environment at 40°C for 18 days or longer. In an embodiment of the invention, the chromium-free anti-corrosion coating composition comprises a corrosion-inhibiting composition comprising rust-preventive particles containing at least one lithium phosphate compound, wherein the rust-preventive particles have a lithium content of at least 1.0% by weight. As described above, rust-preventive particles refer to powdered particles mainly composed of at least one lithium phosphate compound, wherein the lithium phosphate compound is an important component providing the anti-corrosion effect for the rust-preventive particles. As the name suggests, a lithium phosphate compound refers to a compound containing lithium cations and phosphate anions. Depending on the need, such lithium phosphate compounds may also be doped with one or more other cations and / or anions. For example, such lithium phosphate compounds may be doped with fluoride ions, hydroxide ions, and / or other anions that do not adversely affect the anti-corrosion performance of the lithium phosphate compound, and / or aluminum ions, calcium ions, iron ions, magnesium ions, manganese ions, strontium ions, nickel ions, and / or other cations that do not adversely affect the anti-corrosion performance of the lithium phosphate compound. As is well known, lithium phosphate compounds are not commonly used components in the formulation of anti-corrosion coating compositions in the coating industry. However, the inventors of this invention have surprisingly discovered that in the formulation of chromium-free anti-corrosion coating compositions, the inclusion of rust-inhibiting particles containing at least one lithium phosphate compound and having a lithium content of at least 5% by weight in the corrosion-inhibiting composition can result in a paint film with excellent corrosion resistance, for example, it can be stored in a water environment at 40°C for 18 days or longer without bubbling, which was unforeseen before this invention. Not bound by any theory, the inventors of this invention have discovered that in a corrosive environment, the lithium phosphate compound contained in the coating formed by the above-mentioned anti-corrosion coating composition can release and / or leachable lithium ions. The dissociated lithium ions act as a cathode inhibitor, reacting with oxygen, water, etc., in the environment to form a passivation layer that protects the metal substrate from external corrosion. Over time, the rust-inhibiting particles, due to their significantly higher lithium ion content, can continuously replenish the lithium ions consumed by oxygen, water, etc., in the environment, thus forming an anti-corrosion coating with longer water resistance. For example, in some embodiments of the invention, the paint film formed by the anti-corrosion coating composition according to the invention can remain blister-free in a water environment at 40°C for 18 days or longer, even 30 days or longer, or even 50 days. In other words, in the corrosion-inhibiting composition of the invention, the rust-inhibiting particles containing at least one lithium phosphate compound and having a lithium content of at least 5% by weight result in a coating with acceptable corrosion resistance, particularly long-term water resistance. In an embodiment of the invention, the rust-preventive particles have a lithium content of at least 1.0% by weight, the lithium content being determined by XPS elemental analysis. Preferably, the rust-preventive particles have a lithium content of at least 5.0% by weight, preferably 5.5% by weight or higher, more preferably 6.0% by weight or higher, even more preferably 6.5% by weight or higher, and even more preferably 7.0% by weight or higher, for example 7.5% by weight or higher or 8.0% by weight or higher, but not exceeding 15.0% by weight, preferably not exceeding 12% by weight, and more preferably not exceeding 10% by weight. If the lithium content of the rust-preventive particles is too low, the anti-corrosion coating composition formulated from them cannot form an anti-corrosion coating with longer water resistance; if the lithium content of the rust-preventive particles is too high, then the activity of such rust-preventive particles is too high, making them unsuitable for formulating anti-corrosion coating compositions. In some embodiments of the invention, the at least one lithium phosphate compound contained in the rust-preventive particles has a spatially stable crystal structure, preferably a triclinic crystal structure, which remains substantially stable even when lithium ions undergo intercalation / deintercalation. Such a spatially stable lithium phosphate compound is particularly suitable for use as an anti-corrosion or anti-rust pigment / filler. Unbound by any theory, the inventors believe that in corrosive environments (e.g., 5% sodium chloride aqueous spray at 35°C for up to 500 hours or longer), the lithium phosphate compound contained in the coating formed by the anti-corrosion coating composition of the invention can, on the one hand, release or leach lithium ions therein. The dissociated lithium ions act as cathode inhibitors, reacting with oxygen, water, etc., in the environment to form a passivation layer that protects the metal substrate from external corrosion; on the other hand, the crystal structure of the lithium phosphate compound remains stable during lithium ion dissociation and does not collapse, thus ensuring that the coating maintains a certain strength without losing adhesion, thereby achieving an anti-corrosion effect. In some embodiments of the present invention, the rust-preventive particles may contain at least one other metallic element in addition to the aforementioned lithium phosphate compound, including one or more of aluminum, calcium, iron, magnesium, manganese, strontium, and nickel. In some embodiments of the present invention, the rust-preventive particles may also contain at least one silicon element in addition to the aforementioned lithium phosphate compound. The inventors of the present invention have discovered that the aforementioned metallic elements such as aluminum, calcium, iron, magnesium, manganese, strontium, and nickel, as well as the silicon element present in the rust-preventive particles according to the present invention can promote or enhance the corrosion-preventive properties of lithium phosphate compounds. Not bound by any theory, the inventors believe that when the anti-corrosion coating of this invention is under corrosive conditions, at least some of the other metallic elements (such as aluminum, iron, calcium, magnesium, manganese, etc.) present in the rust-preventing particles will be released. These released free metal ions can combine with lithium phosphate compounds to form free phosphate ions after lithium dissociation, thereby forming a passivation layer and improving the anti-corrosion performance of lithium phosphate compounds. When aluminum metal elements are present in the rust-preventing particles, these particles can release and / or leachable aluminum ions. The dissociated aluminum ions combine with the aforementioned dissociated lithium ions, oxygen, water, etc. in the environment, resulting in an anti-corrosion effect similar to that of water-soluble lithium salts on metallic aluminum substrates, i.e., forming insoluble LixAly(OH). z This allows the rust-preventive particles to form a synergistic anti-corrosion effect. Furthermore, the silicon element present in the rust-preventive particles (usually in the form of silicates) can be partially dissolved, and the dissolved SiO₂... 3 2- Ferric silicate (Fe) reacts with iron ions from the metal substrate at the coating / metal interface to form ferric silicate. 2(SiO 3) 3) Protective layer, at the same time, the dissolved SiO 3 2- It can also react with other metal cations (such as iron, calcium, magnesium, manganese, etc.) derived from rust-inhibiting particles at the coating / metal interface, thus forming calcium silicate (CaSiO₂) at the metal interface. 3) Ferric silicate (Fe 2(SiO 3) 3) Manganese silicate (Mn) 2SiO 3) Protective film. The above-mentioned iron silicate, calcium silicate, iron silicate, manganese silicate, etc. are deposited together to form a composite protective film layer on the metal interface, thereby improving the corrosion resistance of lithium phosphate compounds. In some embodiments of the invention, the rust-preventive particles are powders with a micron scale, preferably with a particle size of less than 50 microns, more preferably with a particle size of less than 40 microns, even more preferably with a particle size of less than 35 microns, and even more preferably with a particle size of less than 30 microns, but the particle size is 1 micron or larger. In some embodiments of the invention, the rust-preventive particles are derived from lithium phosphate aluminum filler, for example, from 800-mesh powder particles that can be obtained by grinding lithium phosphate aluminum filler. In addition to the lithium phosphate compounds, other metallic elements, and silicon elements mentioned above, the rust-preventing particles according to the present invention may further contain other components that will not adversely affect the performance of the rust-preventing particles, the anti-corrosion coating composition formulated therefrom, and the anti-corrosion coating obtained therefrom. In some embodiments of the present invention, the rust-inhibiting particles containing at least one lithium phosphate compound are alkaline, having a pH of at least 8.0. Preferably, the pH of the rust-inhibiting particles containing at least one lithium phosphate compound is in the range of 8.0 to 11.5, more preferably in the range of 8.5 to 11.2. In one embodiment of the present invention, the pH of the rust-inhibiting particles containing at least one lithium phosphate compound is in the range of 8.5 to 9.0. In another embodiment of the present invention, the pH of the rust-inhibiting particles containing at least one lithium phosphate compound is in the range of 9.0 to 11.2. The aforementioned rust-inhibiting particles containing at least one lithium phosphate compound can be any known commercially available product, or they can be homemade. In one embodiment of the invention, the rust-inhibiting particles containing at least one lithium phosphate compound are obtained from lithium phosphate aluminum filler purchased from Yung Hsing Materials Co., Ltd. by a grinding mill. Preferably, the rust-inhibiting particles containing at least one lithium phosphate compound are present in an amount of 5% by weight or higher, preferably 6% by weight or higher, but not exceeding 20% ​​by weight, relative to the total weight of component A. In one specific embodiment of the invention, the rust-inhibiting particles containing at least one lithium phosphate compound are present in an amount of about 5 to 18% by weight, or about 5 to 15% by weight, or about 5.5 to 10% by weight, or about 5.5 to 8% by weight, or about 5.5 to 7.5% by weight, relative to the total weight of component A. In an embodiment of the invention, the corrosion-inhibiting composition contained in the chromium-free anti-corrosion coating composition further comprises at least one cation-exchange silicone. As described above, the cation-exchangeable silica gel refers to amorphous silica with cations adsorbed or attached to it, which can exchange with specific cations (e.g., hydrogen ions). When the coating is in a corrosive environment, corrosive ions such as hydrogen ions penetrate the coating film. + ), on the surface of silicone particles, cations (such as calcium ions (Ca) 2+The cations exchange with the substrate, and the resulting released cations then migrate to the interface of the metal substrate, further forming a protective film on the metal substrate interface. Thus, cation-exchange silicone can not only adsorb corrosive ions from the environment but also form a protective film on the cross-section of the metal substrate. Not bound by any particular theory, the inventors believe that cation-exchange silicone can form a protective film at the interface between the metal substrate and the coating as follows: Under corrosive conditions, a metal substrate such as iron is oxidized to ferrous ions (Fe²⁺) in the anodic region. 2+ Then it is further oxidized to iron ions (Fe). 3+ Meanwhile, oxygen (O2) in the air 2) and moisture (H) OH⁻ can penetrate the organic coating and reach the interface between the coating and the metal substrate, where it is reduced to hydroxide ions; this is known as the cathodic reaction. Based on the presence of OH⁻ in the coating... - Different concentrations of amorphous silica (SiO2) in cation exchange silicone affect its composition. 2) It can dissolve to some extent into silicate ions (SiO₂). 3 2- The generated SiO 3 2- It reacts with iron ions at the coating / metal interface to form ferric silicate (Fe). 2(SiO 3) 3) Protective layer; simultaneously, cations (e.g., Ca) released from the cation exchange silicone... 2+ (cations) and soluble SiO 3 2- A reaction occurs, thus forming calcium silicate (CaSiO₂) in the alkaline region of the metal interface. 3) Protective film. CaSiO 3 and Fe 2(SiO 3) 3. They are deposited together to form a composite protective film layer on the metal interface. In addition, cations released from the cation-exchange silicone (e.g., Ca) 2+ The cations can also react with phosphate and OH groups released from the coating system. - An interaction occurs, producing calcium phosphate (Ca). 3(PO 4) 2) It reacts with water molecules to form a calcium phosphate barrier layer that prevents oxygen from approaching the surface of the metal substrate. Therefore, it is preferable to include cation-exchange silicone in the corrosion-inhibiting composition, as it acts as a reinforcing agent to further enhance the anti-corrosion effect of rust-inhibiting particles containing at least one lithium phosphate compound. In some embodiments of the invention, the cation exchange silicate is porous. A porous structure is advantageous because it can carry a larger amount of cations, thus facilitating the formation of the aforementioned protective film. In some embodiments of the invention, the cation exchange silicate is alkaline or neutral, having a pH of at least 7.0. Preferably, the pH of the cation exchange silicate is in the range of 7.0 to 11.5, more preferably in the range of 7.5 to 11.2. In one embodiment of the invention, the pH of the cation exchange silicate is in the range of 7.5 to 9.0. In another embodiment of the invention, the pH of the cation exchange silicate is in the range of 9.0 to 11.2. In some embodiments of the present invention, the at least one cation exchange type silicone includes magnesium ion exchange type silicone, barium ion exchange type silicone, aluminum ion exchange type silicone, and calcium ion exchange type silicone. In a preferred embodiment of the present invention, the at least one cation exchange type silicone includes calcium ion exchange type silicone. Preferably, the cation-exchange silicone is present in an amount of 0.5% by weight or higher, preferably 1% by weight or higher, but not exceeding 5.0% by weight, relative to the total weight of component A. In one specific embodiment of the invention, component A comprises about 1.0 to 2.5% by weight of cation-exchange silicone, or about 1.5 to 2.5% by weight of cation-exchange silicone, or about 1.5 to 2.0% by weight of cation-exchange silicone, or about 1.0 to 2.0% by weight of cation-exchange silicone, or about 1.5 to 1.8% by weight of cation-exchange silicone, relative to the total weight of component A. In some embodiments of the invention, the corrosion-inhibiting composition included in the chromium-free anti-corrosion coating composition may optionally contain one or more other corrosion inhibitors. Preferably, however, the corrosion-inhibiting composition included in the chromium-free anti-corrosion coating composition is substantially free of other corrosion inhibitors, more preferably completely free of other corrosion inhibitors. The inventors of the present invention have found with particular surprise that, in addition to the aforementioned rust-inhibiting particles containing at least one lithium phosphate compound and cation-exchange silicone, the incorporation of other commonly used chromium-free corrosion inhibitors in the art, such as aluminum tripolyphosphate and organic corrosion inhibitors, into the anti-corrosion inhibitor composition according to the invention adversely affects the anti-corrosion performance of the resulting coating, which was unforeseen prior to the present invention. In some embodiments of the invention, the corrosion-inhibiting composition comprises, relative to the total weight of the corrosion-inhibiting composition, at least 70% by weight, at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 95% by weight, or even up to 100% by weight of rust-inhibiting particles containing at least one lithium phosphate compound. In some embodiments of the invention, preferably, component A comprises about 6% to about 15% by weight of a corrosion-inhibiting composition relative to the total weight of component A. In some embodiments of the invention, component A comprises at least about 6% by weight, or at least about 6.5% by weight, or at least about 7% by weight, or at least about 8% by weight of a corrosion-inhibiting composition relative to the total weight of component A. In the above embodiments of the invention, component A comprises less than about 15% by weight, or less than about 13% by weight, or less than about 12% by weight of a corrosion-inhibiting composition relative to the total weight of component A. In some embodiments of the invention, the chromium-free anti-corrosion coating composition is a two-component coating composition comprising component A and component B, wherein component A includes a film-forming composition, a corrosion-inhibiting composition, an optional carrier, and additional additives, and component B includes a curing agent. Before application, component A and component B are mixed, and then application is carried out. In other embodiments of the invention, the chromium-free anti-corrosion coating composition is a one-component coating composition comprising component A, which includes a film-forming composition, a corrosion-inhibiting composition, an optional carrier, and additional additives. In these embodiments, the film-forming composition can be cured into a film by, for example, self-crosslinking. In embodiments of the present invention, a film-forming composition refers to a composition constituting the main body of a coating formed by a chromium-free anti-corrosion coating composition, which contains a resin component and may also contain inorganic silicate film-forming substances independently or additionally. In some embodiments of the invention, inorganic silicate film-forming substances are used to provide film-forming compositions for chromium-free anti-corrosion coating compositions. On one hand, these inorganic silicates act as binders, providing adhesion between the coating and the substrate, and holding the components (such as fillers) in the coating composition together and imparting a certain cohesive strength to the paint film. Chromium-free anti-corrosion coating compositions using such inorganic silicates as film-forming substances also have the additional beneficial effect of abrasion resistance, and have therefore attracted attention in recent years. In some embodiments of the invention, a resin component is used to provide a film-forming composition for a chromium-free anti-corrosion coating composition. The resin component may be selected, for example, from at least one of epoxy resins, chlorinated resins, polyaspartic esters, alkyd resins, phenolic resins, polyurethanes, polysiloxanes, polyester resins, and acrylic resins. In a presently preferred embodiment, the resin component may be selected from at least one of epoxy resins, polyester resins, and acrylic resins. In a presently more preferred embodiment, the resin component may be selected from epoxy resins. In a preferred embodiment of the invention, the resin component is an epoxy resin. The term "epoxy resin" refers to a polymer or oligomer containing two or more epoxy groups per molecule. Preferably, each molecule of an epoxy resin may contain up to four epoxy groups. Preferably, each molecule of an epoxy resin may contain two or three epoxy groups. According to certain embodiments of the invention, the epoxy resin may have an epoxy equivalent that varies over a wide range, where epoxy equivalent refers to the quality of the epoxy resin containing 1 mol of epoxy groups. For example, the epoxy resin may comprise low epoxy equivalent epoxy resins, high epoxy equivalent epoxy resins, or combinations thereof. In this document, epoxy resins with an epoxy equivalent that can be between 400-700 g / eq, preferably between 450-550 g / eq, are referred to as low epoxy equivalent epoxy resins. Epoxy resins with a higher epoxy equivalent, such as an epoxy equivalent greater than 800 g / eq, are referred to as high epoxy equivalent epoxy resins. Preferably, the epoxy equivalent of the high epoxy equivalent epoxy resin can be in the range of 900 g / eq to 2500 g / eq. In some embodiments, the epoxy equivalent of the high epoxy equivalent epoxy resin can be in the range of 850 g / eq to 1200 g / eq. In some embodiments, the epoxy equivalent of the high epoxy equivalent epoxy resin can be in the range of 1400 g / eq to 2500 g / eq, for example, in the range of 1600-1800 g / eq, or in the range of 1700-2200 g / eq. Suitable epoxy resins include, for example, diglycidyl ethers of polyphenols, such as diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol A, bisphenol F, bisphenol S, and tetramethylbisphenol; diglycidyl ethers of polyols, such as diglycidyl ethers of aliphatic glycols and polyether glycols, for example, C... 2-24 Diglycidyl ethers of alkylene glycols, diglycidyl ethers of poly(ethylene oxide) glycols, or diglycidyl ethers of poly(propylene oxide) glycols; polyglycidyl ethers of phenolic resins, such as polyglycidyl ethers of phenol-formaldehyde resins, polyglycidyl ethers of alkyl-substituted phenol-formaldehyde resins, polyglycidyl ethers of phenol-hydroxybenzaldehyde resins, or polyglycidyl ethers of cresol-hydroxybenzaldehyde resins; or combinations thereof. According to certain embodiments of the present invention, the epoxy resin is a diglycidyl ether of a polyphenol, and is particularly preferably having the following structural formula (I): Where D represents -S-, -SS-, -SO-, -SO 2-、-CO 2-, -CO-, -O- or divalent alkyl groups having 1 to 10, preferably 1 to 5, more preferably 1 to 3 carbon atoms, such as -CH 2- or -C(CH) 3) 2-; Each Y is independently a halogen, such as F, Cl, Br, or I, or optionally a monovalent C that can be substituted. 1-C 10 Hydrocarbon groups, such as optionally substituted methyl, ethyl, vinyl, propyl, allyl, or butyl groups; Each m is independently 0, 1, 2, 3, or 4; and n is an integer from 0 to 4, such as 0, 1, 2, 3, or 4. More preferably, the epoxy resin is a bisphenol A type epoxy resin, a bisphenol S type epoxy resin, or a bisphenol F type epoxy resin having the structural formula (I), wherein D represents -C(CH) 3) 2-、-SO 2- or -CH 2-, m represents 0, and n is an integer from 0 to 4. Most preferably, the epoxy resin is a bisphenol A type epoxy resin having structural formula (I), wherein each D represents -C(CH) 3) 2-, m represents 0, and n is an integer from 0 to 4. The epoxy resins disclosed above can be manufactured, for example, using epichlorohydrin technology well known to those skilled in the art. Examples of epoxy resins include any conventional epoxy resin, such as E55, E51, E44, and E20 from Shanghai Kaiping Resin Co., Ltd., or epoxy resins existing in the form of waterborne epoxy resin emulsions, such as Allnex 387 from American Abrasives, 3907 from Huntsman, 900 and 1600 from Nanya, or EPIKOTE from Hansen. TM Resin 6520. Preferably, the aqueous epoxy resin emulsion has a solid content of 40-60% by weight. In another preferred embodiment of the invention, the resin component comprises a polyester resin. The term "polyester resin" herein refers to a liquid polyester resin prepared by condensation polymerization of a polyol and a polyacid or anhydride. Representative polyols include glycerol, pentaerythritol, sorbitol, trimethylolpropane, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and other polyols known to those skilled in the art as being suitable for preparing polyester resins. Representative polyacids or anhydrides include diacids or anhydrides such as phthalic acid and its anhydrides, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, etc.; tricarboxylic acids such as trimellitic acid; and other polyacids or anhydrides known to those skilled in the art as being suitable for preparing polyester resins. As described above, polyester resins can be prepared using appropriate preparation methods well known to those skilled in the art, or can be obtained from any suitable commercially available product. Commercial examples of polyester resins include those commercially available from DSM GmbH (Netherlands) with designations SH970, SH973, SH974, SN800, and SN908; those commercially available from SK Chemicals with designations ES-300, ES-410, ES-450, ES-901, ES-910, ES-955, ES-960, and ES-980; or those commercially available from Degussa with designations L205, L210, L411, LH820, LH833, LH818, and LH910. In another embodiment of the invention, the resin component comprises an acrylic resin. The acrylic resin suitable for use in this invention can be a water-dispersible acrylic resin, which can be prepared using techniques well known to those skilled in the art. For example, the acrylic resin can be a copolymer of various olefinically unsaturated compounds. Examples of suitable olefinically unsaturated monomers include vinyl and vinylidene monomers, such as styrene, α-methylstyrene, o- and p-chlorostyrene, o-, m- and p-methylstyrene, p-tert-butylstyrene, acrylic acid, (meth)acrylonitrile, acrylates and methacrylates having 1 to 8 carbon atoms (such as ethyl acrylate, methyl acrylate, n- or isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and isooctyl methacrylate). Diesters of fumaric acid, itaconic acid, or maleic acid having 4 to 8 carbon atoms in the alcohol component; (meth)acrylic acid amide; vinyl esters of alkane monocarboxylic acids having 2 to 5 carbon atoms (e.g., vinyl acetate or vinyl propionate); and hydroxyalkyl esters of acrylic acid or methacrylic acid having 2 to 4 carbon atoms in the hydroxyalkyl residue (e.g., 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropyl acrylate or methacrylate, 4-hydroxybutyl acrylate or methacrylate, trimethylolpropane monoacrylate or methacrylate or pentaerythritol monoacrylate or methacrylate). Mixtures of these monomers are also suitable. As an example of acrylic resins, any conventional acrylic resin can be used, such as Sherwin-Williams' own acrylic resin 476706. The aforementioned resin component is used to provide a film-forming composition for chromium-free anti-corrosion coating compositions. On one hand, this resin component acts as a binder, providing adhesion between the coating and the substrate, and holding the components in the coating composition (such as fillers) together and imparting a certain cohesive strength to the paint film. On the other hand, this resin component can exhibit good reactivity with a curing agent (if present), thereby achieving a coating with higher mechanical strength. Preferably, the chromium-free anti-corrosion coating composition comprises about 30% to about 70% by weight of a film-forming composition relative to the total weight of component A. In some embodiments of the invention, the chromium-free anti-corrosion coating composition comprises at least about 32% by weight, or at least about 34% by weight, or at least about 40% by weight, or at least about 45% by weight of a film-forming composition relative to the total weight of component A. In the above embodiments of the invention, the chromium-free anti-corrosion coating composition comprises less than about 65% by weight, or less than about 60% by weight, or less than about 55% by weight of a film-forming composition relative to the total weight of component A. If necessary, the chromium-free anti-corrosion coating composition may also contain a curing agent for the resin component, the type of which depends on the nature of the resin component. The coating composition containing epoxy resin preferably contains an aliphatic or aromatic amine curing agent, a polyamide curing agent, or a thiol-based curing agent. Suitable amine curing agents are aliphatic amines and their adducts (e.g., 2021), phenalkamines, cyclic alicyclic amines (e.g., 2196), amide amines (e.g., 2426), polyamides and their adducts, and mixtures thereof. Coating compositions containing amino and / or hydroxyl functional resins preferably use isocyanates and isocyanurates as curing agents. Suitable isocyanate curing agents are aliphatic, alicyclic, and aromatic polyisocyanates, such as trimethylene diisocyanate, 1,2-propylidene diisocyanate, tetramethylene diisocyanate, 2,3-butylidene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dodecanethylene diisocyanate, 1,3-cyclopentylene diisocyanate, 1, 2-Cyclohexylene diisocyanate, 1,4-Cyclohexylene diisocyanate, 4-methyl-1,3-cyclohexylene diisocyanate, m- and p-phenylene diisocyanate, 1,3- and 1,4-bis(isocyanate methyl)benzene, 1,5-dimethyl-2,4-bis(isocyanate methyl)benzene, 1,3,5-triisocyanate benzene, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,4,6-toluene triisocyanate, α,α,α ',α '-Tetramethyl-o-,-, and-p-xylene diisocyanate, 4,4 '-Diphenylene diisocyanate methane, 4,4 '-Diphenylene diisocyanate, 3,3 '-Dichloro-4,4 '-Diphenylene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, trans-ethylene diisocyanate, and mixtures thereof. Adducts of the above polyisocyanates are also suitable, such as biuret, isocyanurate, allophonate, uretdione, and mixtures thereof. Depending on the application, the above isocyanates and their adducts may be present in the form of capped or latent isocyanates. In the two-component chromium-free anti-corrosion coating composition according to the present invention, the amount of curing agent as component B can be adjusted based on the amount of component A, particularly the amount of film-forming composition in component A, according to the experience of those skilled in the art. In some embodiments of the present invention, the weight ratio of component A to component B as curing agent can be 100:15, 100:23, 100:30, or other commonly used ratios of component A to component B in the art. In embodiments of the invention, a carrier is optional in the formulation of the chromium-free anti-corrosion coating composition. In some embodiments of the invention, the chromium-free anti-corrosion coating composition does not contain a carrier and is present in the form of a powder coating composition. In some embodiments of the invention, the chromium-free anti-corrosion coating composition may contain a carrier and is present in the form of a solvent-based coating composition or a water-based coating composition. If present, the carrier includes water, water-miscible organic solvents, water-immiscible organic solvents, or combinations thereof, thereby reducing the adhesion of the coating composition for coating. The addition of organic solvents can increase the evaporation rate of the anti-corrosion coating composition and accelerate film formation. In some embodiments of the invention, the organic solvent includes ketones (e.g., acetone, methyl isopropyl ketone, methyl isobutyl ketone, etc.), alcohols (propanol, benzyl alcohol, etc.), esters (ethyl acetate, butyl acetate, etc.), aromatic hydrocarbons (toluene, xylene, etc.), aliphatic hydrocarbons (cyclopentane, cyclohexane, etc.), or any combination thereof. In a preferred embodiment of the invention, if present, the carrier may, for example, comprise at least about 5% by weight, at least about 6% by weight, at least about 7% by weight, at least about 8% by weight, at least about 9% by weight, and at least about 10% by weight of the total weight of component A. In a preferred embodiment of the invention, if present, the carrier may, for example, comprise at most about 15% by weight, at most about 14% by weight, at most about 13% by weight, or at most about 12% by weight of the total weight of component A. Typically, the desired amount of carrier is empirically selected based on the film-forming properties of the coating. In embodiments of the present invention, the chromium-free anti-corrosion coating composition may optionally further comprise commonly used additives. Suitable additives may include fillers, wetting and dispersing agents, defoamers, leveling agents, additional corrosion inhibitors, adhesion promoters, film-forming aids, rheology modifiers, or any combination thereof. The amounts of the aforementioned optional components are sufficient to achieve their intended purpose, but preferably, such amounts will not adversely affect the coating composition or the coating obtained therefrom. According to certain embodiments of the invention, the total amount of the additional additives relative to the total weight of component A is in the range of about 0% by weight to about 50% by weight, preferably in the range of about 0.1% by weight to about 40% by weight. In one specific embodiment of the invention, component A of the chromium-free anti-corrosion coating composition comprises, relative to the total weight of said component A, 30-70% by weight of film-forming composition; 6-15% by weight of corrosion-inhibiting composition; 0-15% by weight of the carrier; 0-50% by weight of additional additives, preferably 0.1-40% by weight of additional additives. In a more specific embodiment of the invention, component A of the chromium-free anti-corrosion coating composition comprises, relative to the total weight of said component A, 30-70% by weight of film-forming composition; 5-20% by weight of rust-preventive particles; 0.5-5% by weight of cation exchange silicone; 0-15% by weight of the carrier; 0-50% by weight of additional additives, preferably 0.1-40% by weight of additional additives. The anti-corrosion coating composition of the present invention can be prepared by any suitable mixing method known to those skilled in the art. For example, the coating composition can be prepared by adding a film-forming composition, rust-inhibiting particles containing a lithium phosphate compound, a cation-exchange silicone, a carrier (if any), and additional additives (if any) to a container, and then stirring the resulting mixture until homogeneous to form component A. The curing agent, as component B, can be present as a single component or, if desired, can be mixed with the above components in a mixture form. The resulting chromium-free anti-corrosion coating composition can be used as a primer in combination with a conventional topcoat, or it can be used alone as a combined primer and topcoat composition to provide the required anti-corrosion performance to the metal substrate. In some preferred embodiments of the invention, the chromium-free anti-corrosion coating composition is a primer. In this embodiment, the chromium-free anti-corrosion coating composition is a water-based coating composition. Preferably, this water-based coating composition is suitable not only for wet-on-wet systems but also for wet-on-dry systems, and the topcoat suitable for use with the primer can be a two-component polyurethane. As described above, the inventors of the present invention have surprisingly discovered that the anti-corrosion coating composition prepared as described above can achieve water resistance when used as a primer or as a topcoat, and more preferably, can achieve excellent salt spray resistance while exhibiting excellent water resistance. In one embodiment of the invention, the above-described coating composition is applied as a base coat to form a dry film thickness of 40-70 micrometers on a sandblasted steel plate and cured. Then, cross-shaped scratches are made on the resulting film to form a test sample. After being subjected to a salt spray test according to ASTM B117 or GB / T1771 for 500 hours or longer, the formed test sample shows a single-sided peel width of 2 mm or less. In one embodiment of the invention, the above-described coating composition is applied as a base coat to form a dry film thickness of 40-70 micrometers on a sandblasted steel plate and cured. The resulting film is then soaked in water at room temperature for 500 hours and in water at a temperature higher than 40°C for 18 days or longer, after which it is substantially free of blistering, preferably completely free of blistering. The inventors of this invention were even more surprised to discover that using a wet-to-dry or wet-to-wet process, combining the above-prepared anti-corrosion coating composition as a primer with a conventional topcoat (e.g., waterborne polyurethane topcoat), both exhibited excellent salt spray resistance and water resistance, which was unexpected. As mentioned earlier, a wet-to-wet process involves applying a second coat of paint before the first coat has fully dried. In the field of coatings, especially anti-corrosion coatings, the wet-to-wet process is a more demanding process. It is well known that when the primer is not fully dry, the topcoat usually reacts with the primer, resulting in insufficient cross-linking of the primer, thus making it susceptible to corrosion. However, the inventors of this invention were particularly surprised to find that the anti-corrosion coating composition according to this invention is particularly suitable as a primer in a wet-to-wet system, not only avoiding application problems such as sagging and wrinkling, but also achieving excellent anti-corrosion performance, which was unforeseen before this invention. As an example, a wet-to-wet process includes, for example, the following steps: applying a primer, leveling at room temperature for 15 minutes, spraying a topcoat, leveling for at least 20 minutes, and then curing at 60°C for at least 12 hours. As an example, a wet-to-dry process includes, for example, the following steps: applying a primer, leveling at room temperature for 15 minutes, curing at 60°C for at least 12 hours, spraying a topcoat, leveling for at least 20 minutes, and then curing at 60°C for at least 12 hours, for example, at least 20 hours. In one embodiment of the invention, using a wet-to-dry process, the above-described coating composition is applied as a primer to form a dry film thickness of 40-70 micrometers on a sandblasted steel plate and cured. Then, a polyurethane topcoat is applied to the dried primer to form a dry film thickness of 40-70 micrometers and cured. Cross-shaped scratches are then made on the resulting film to form a test sample. After being subjected to a salt spray test according to ASTM B117 or GB / T1771 for 500 hours or longer, the formed test sample can show a single-sided peel width of 3 mm or less, preferably 2 mm or less. In one embodiment of the invention, the above-described coating composition is applied as a primer to a sandblasted steel plate in a wet-on-wet process to form a dry film thickness of 40-70 micrometers. Immediately afterwards, a polyurethane topcoat is applied to the wet primer in a dry film thickness of 40-70 micrometers and cured. Then, cross-shaped scratches are made on the resulting film to form a test sample. After undergoing a salt spray test according to ASTM B117 or GB / T1771 for a period of 500 hours or longer, preferably 700 hours or longer, the formed test sample can show a single-sided peel width of 3 mm or less, preferably 2 mm or less. In one embodiment of the invention, using a wet-to-dry process, the above-mentioned coating composition is applied as a primer to form a dry film thickness of 40-70 micrometers on a sandblasted steel plate and cured. Then, a polyurethane topcoat is applied to the dried primer to form a dry film thickness of 40-70 micrometers and cured. The resulting film is then immersed in water at room temperature for 500 hours and / or in water at a temperature higher than 40°C for 18 days or longer. The resulting coating exhibits a substantially non-bubbly appearance, preferably a completely non-bubbly appearance. In one embodiment of the invention, the above-mentioned coating composition is applied as a primer to a sandblasted steel plate in an amount of 40-70 micrometers dry film thickness using a wet-on-wet process. Immediately afterwards, a polyurethane topcoat is applied to the wet primer in an amount of 40-70 micrometers dry film thickness and cured. The resulting coating film is then immersed in water at room temperature for 500 hours and / or in water at a temperature higher than 40°C for 18 days or longer. The resulting coating exhibits a substantially non-bubbly appearance, preferably a completely non-bubbly appearance. Another aspect of the present invention provides an article comprising: a metal substrate; and a coating formed by the chromium-free anti-corrosion coating composition of the present invention directly applied to the metal substrate. As described above, the chromium-free anti-corrosion coating composition of the present invention can be used as a primer or as a combined primer and topcoat. Therefore, in some embodiments of the present invention, the article comprises a metal substrate; a primer layer formed by the chromium-free anti-corrosion coating composition of the present invention directly applied to the metal substrate; and a topcoat layer formed by a conventional topcoat in the art (e.g., a waterborne polyurethane topcoat) applied to the primer. In other embodiments of the present invention, the article comprises a metal substrate; and a coating formed by the chromium-free anti-corrosion coating composition of the present invention directly applied to the metal substrate. As the metal substrate for manufacturing the articles of the present invention, any suitable metal substrate known in the art can be used. As an example, the metal substrate is selected from one or more of steel, iron, aluminum, zinc, copper, and alloys. According to the present invention, the article can be prepared, for example, by the following steps: (1) providing a polished metal substrate; (2) sequentially coating and forming one or more chromium-free anti-corrosion coating compositions of the present invention on the metal substrate using a coating and curing process to provide anti-corrosion properties to the metal substrate. According to the present invention, the resulting metal articles may be further treated with an anti-corrosion topcoat and are used for end applications including, but not limited to: refrigerated and non-refrigerated transport containers (e.g., dry cargo containers) derived from suppliers or manufacturers including China International Marine Containers (CIMC), Graaff Transportsysteme GmbH, Maersk Line, and other suppliers or manufacturers well known to those skilled in the art; chassis, trailers (including semi-trailers), rail vehicles, truck bodies, ships, bridges, building frames, and prefabricated or on-site metal components requiring temporary indoor or outdoor corrosion protection during manufacturing. Additional uses include metal corners, passageways, beams (e.g., I-beams), pipes, tubes, plates, or other components that can be welded into these or other metal components. The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available and ready for use without further processing. Example Test methods Salt spray resistance: As needed, the anti-corrosion coating composition is applied as a primer or as a combined primer and topcoat to a sandblasted steel plate to form a dry film thickness of 40-70 micrometers and then cured to form a test sample. When the anti-corrosion coating composition is used as a primer, the test sample also includes a topcoat layer, formed by a commercially available waterborne polyurethane topcoat WKY0305 from Valspar, with a dry film thickness between 40-70 micrometers, applied over the primer. The resulting test samples are then subjected to salt spray testing for 500 hours or longer according to ASTM B117 or GB / T1771, and the unilateral peel width of the scratches is measured. If the unilateral peel width exceeds 2 mm after 500 hours of salt spray testing or exceeds 3 mm after 700 hours of salt spray testing, the test sample is considered unqualified and has poor wet adhesion. If the unilateral peel width is 2 mm or less after 500 hours of salt spray testing and 3 mm or less after 700 hours of salt spray testing, the test sample is considered qualified. Water resistance: As needed, the anti-corrosion coating composition is applied as a primer or as a combined primer and topcoat to a sandblasted steel plate to form a dry film thickness of 40-70 micrometers and then cured to form a test sample. When the anti-corrosion coating composition is used as a primer, the test sample also includes a topcoat layer, formed by a commercially available waterborne polyurethane topcoat WKY0305 from Valspar, with a dry film thickness between 40-70 micrometers, applied over the primer. The test samples were then immersed in water at room temperature for 500 hours or in water at a temperature higher than 40°C for 18 days, and the coating surface was visually inspected for blistering. If the coating blistered after immersion in water at room temperature for 500 hours or in water at a temperature higher than 40°C for 18 days, the test sample was considered unqualified. If the coating did not blister after immersion in water at room temperature for 500 hours or in water at a temperature higher than 40°C for 18 days, the test sample was considered qualified. Epoxy resin-based anti-corrosion coating composition As shown in Table 1, the components in component A are mixed to obtain component A, which is then mixed with component B curing agent to form the epoxy resin-based anti-corrosion coating composition according to Examples 1-7 of the present invention. *In the salt spray test of Example 7, the coating film underwent 320 hours; As shown in Examples 1-7, in the anti-corrosion coating compositions according to the present invention, rust-inhibiting compositions are employed, including rust-inhibiting particles containing lithium phosphate compounds, combinations of rust-inhibiting particles and calcium ion-exchange silica, and combinations of rust-inhibiting particles, calcium ion-exchange silica, and aluminum tripolyphosphate. Then, a water-based polyurethane topcoat is applied to a partially dried primer layer formed from the coating compositions of Examples 1-7 to form a topcoat. The resulting composite coatings are subjected to a water resistance test at 40°C for 18 days and a water resistance test at room temperature for 500 hours, and / or to salt spray tests according to ASTM B117 for at least 500 hours and 700 hours, respectively. As can be seen from the results of Examples 1-6 in Table 1, in the formulation of the chromium-free anti-corrosion coating composition, the corrosion-inhibiting composition contains rust-inhibiting particles containing at least one lithium phosphate compound, resulting in a coating film formed therefrom that remains blister-free for 18 days or longer in a water environment at 40°C and for 500 hours or longer in a water environment at room temperature. Moreover, in the formulation of the chromium-free anti-corrosion coating composition, the corrosion-inhibiting composition contains rust-inhibiting particles containing at least one lithium phosphate compound and cation-exchange silicone, resulting in a coating film that not only exhibits excellent water resistance, demonstrated by the formation of the coating film remaining blister-free for 18 days or longer in a water environment at 40°C and for 500 hours in a water environment at room temperature, but also demonstrates excellent salt spray resistance, demonstrated by the formation of the coating film exhibiting a single-sided peel width of no more than 2 mm after 500 hours of ASTM B117 salt spray testing. To more intuitively demonstrate the salt spray resistance and water resistance of the anti-corrosion coating compositions according to the present invention, photographs of the coatings formed by the coating compositions of Examples 1-6 after water resistance testing are shown in Figures 1-4, and photographs of the coatings formed by the coating compositions of Examples 4-6 after salt spray testing are shown in Figure 5. As can be seen from Figures 1-5, the coatings formed by the chromium-free anti-corrosion coating compositions according to the present invention, comprising a combination of lithium-containing phosphate compound rust-inhibiting particles and calcium ion-exchange silicone, exhibit limited single-sided peel width after undergoing the B117 salt spray test, not exceeding 3 mm, demonstrating excellent salt spray resistance. Furthermore, after immersion in water at 40°C for up to 18 days, the coating surface is smooth and free of blistering, demonstrating excellent water resistance. To further verify the anti-corrosion effect of the rust-inhibiting particles, the inventors replaced the same amount of rust-inhibiting particles in Example 4 with a certain amount of aluminum tripolyphosphate, forming Example 7. A water-based polyurethane topcoat was applied to the undercoat formed by the coating composition of Example 7 before it reached full dryness to form a topcoat. The resulting composite coating underwent a 320-hour salt spray test according to ASTM B117, a 13-day water resistance test at 40°C, and a 600-hour water resistance test at room temperature. The results showed that the coating of Example 7 had excellent water resistance, but its salt spray resistance was significantly lower than that of the coating formed by the coating composition of Example 4. The coating formed by the coating composition of Example 4 had only a 0.93 mm single-sided peel width after a 320-hour salt spray test according to ASTM B117, while the coating formed by the coating composition of Example 7 had a 1.56 mm single-sided peel width after a 320-hour salt spray test according to ASTM B117. Therefore, rust-inhibiting particles containing at least one lithium phosphate compound exhibit significantly better anti-corrosion performance than other chromium-free corrosion inhibitors. In other words, the rust-inhibiting particles containing at least one lithium phosphate compound in the corrosion-inhibiting composition of the present invention can have excellent anti-corrosion and water resistance properties on their own, and do not even need to be compounded with other traditional anti-corrosion substances to improve the corrosion resistance of the coating. This innovation is unprecedented. Although the present invention has been described with reference to numerous embodiments and examples, those skilled in the art will recognize that other embodiments can be designed based on the disclosure of the present invention without departing from the scope of protection of the present invention.

Claims

1. A chromium-free anti-corrosion coating composition comprising: Component A, including a film-forming composition, a corrosion-inhibiting composition, an optional carrier, and additional additives, wherein the corrosion-inhibiting composition comprises: rust-inhibiting particles containing at least one lithium phosphate compound, wherein the rust-inhibiting particles have a lithium content of at least 1.0% by weight; and optionally, Component B, including a curing agent, wherein the at least one lithium phosphate compound has a spatially stable crystal structure; and wherein the rust-inhibiting particles further comprise at least one other metallic element, wherein the at least one other metallic element includes aluminum.

2. The chromium-free anti-corrosion coating composition as described in claim 1, wherein, The rust-preventive particles have a lithium content of at least 5.0% by weight.

3. The chromium-free anti-corrosion coating composition as described in claim 1, wherein, The rust-preventive particles have a lithium content of 7.0% by weight or higher.

4. The chromium-free anti-corrosion coating composition as described in claim 1, wherein, The rust-preventive particles also contain at least one silicon element.

5. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The rust-preventive particles are powders with a micron scale.

6. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The rust-preventive particles have a particle size of less than 50 micrometers.

7. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The at least one lithium phosphate compound has a triclinic crystal structure.

8. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The rust-preventive particles are derived from lithium phosphorus aluminum filler.

9. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The rust-preventive particles are present in an amount of 5% by weight or higher, but not exceeding 20% ​​by weight, relative to the total weight of component A.

10. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The rust-preventive particles are present in an amount of 6% by weight or higher, but not exceeding 20% ​​by weight, relative to the total weight of component A.

11. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The corrosion-inhibiting composition further comprises at least one cation-exchange silicone.

12. The chromium-free anti-corrosion coating composition as claimed in claim 11, wherein, The at least one cation-exchange silicone is porous.

13. The chromium-free anti-corrosion coating composition as claimed in claim 11, wherein, The at least one cation exchange silicone includes one or more of magnesium ion exchange silicone, barium ion exchange silicone, aluminum ion exchange silicone, and calcium ion exchange silicone.

14. The chromium-free anti-corrosion coating composition as claimed in claim 11, wherein, The at least one cation-exchange silicone includes calcium ion-exchange silicone.

15. The chromium-free anti-corrosion coating composition as claimed in claim 11, wherein, The at least one cation-exchange silicone is present in an amount of 0.5% by weight or higher, but not exceeding 5% by weight, relative to the total weight of component A.

16. The chromium-free anti-corrosion coating composition as claimed in claim 11, wherein, The at least one cation-exchange silicone is present in an amount of 1% by weight or higher, but not exceeding 5% by weight, relative to the total weight of component A.

17. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The corrosion-inhibiting composition is alkaline.

18. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The film-forming composition includes at least one of inorganic silicates, epoxy resins, chlorinated resins, polyaspartic acid esters, alkyd resins, phenolic resins, polyurethanes, polysiloxanes, polyester resins, and acrylic resins.

19. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The film-forming composition includes at least one of epoxy resin, polyester resin, and acrylic resin.

20. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The carrier includes water, water-miscible organic solvents, water-immiscible organic solvents, or combinations thereof.

21. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The chromium-free anti-corrosion coating composition is a water-based coating composition.

22. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The chromium-free anti-corrosion coating composition is a solvent-based coating composition.

23. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The chromium-free anti-corrosion coating composition is a powder coating composition.

24. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, Component A comprises, relative to the total weight of Component A, 30-70% by weight of a film-forming composition; 6-15% by weight of a corrosion-inhibiting composition; 0-15% by weight of a carrier; and 0-50% by weight of additional additives.

25. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The chromium-free anti-corrosion coating composition is a primer or a combined primer and topcoat.

26. The chromium-free anti-corrosion coating composition as described in any one of claims 1 to 4, wherein, The chromium-free anti-corrosion coating composition is a primer suitable for wet-on-wet or wet-on-dry systems.

27. A metal article with an anti-corrosion coating, comprising a metal substrate; and a coating formed by a chromium-free anti-corrosion coating composition of any one of claims 1 to 26, applied directly onto the metal substrate.

28. The article of manufacture as claimed in claim 27, wherein, The metal substrate is selected from one or more of steel, iron, aluminum, zinc, copper, and alloys.

29. The article of manufacture as claimed in claim 27, wherein, The metal substrate is steel or iron.

Images