TWI482881B - The surface treatment method of the magnesium-containing substrate and the products thereof, and the polishing liquid and the coating liquid used - Google Patents

Description

Surface treatment method of magnesium-containing substrate and product thereof, and polishing liquid and coating liquid used

The present invention relates to a surface treatment method for a metal substrate, and more particularly to a surface treatment method for a magnesium-containing substrate. The present invention also relates to a laminate obtained by the method of the present invention, and a polishing liquid and a coating liquid used in the method.

The magnesium-containing substrate is favored by, for example, sports equipment and 3C product manufacturers by virtue of its light weight, high specific strength, strong shock absorption, and isolation of electromagnetic interference (EMI). The material of the equipment bracket or the outer casing of the product is preferred. Compared with other metal substrates, the magnesium-containing substrate has higher activity and is more corrosive, so it needs to be subjected to a surface treatment method to enhance its corrosion resistance, and then it is suitable as a component of the desired product, and then participates in the commodity. Assembly.

The surface treatment method can generally be divided into one cleaning step, one passivation step, and a colored coating step.

The cleaning step is for removing an undesired substance such as an oxide, a grease or the like which is originally attached to the surface of the magnesium-containing substrate, and usually, after first casting the magnesium-containing substrate, and then passing through The magnesium-containing substrate is cleaned by repeated rinsing or soaking of an alkali agent, a surfactant solution, an acid agent, or water.

The passivation step is performed by contacting a surface of the magnesium-containing substrate after the cleaning step with a passivation solution, and drying the passivation liquid on the surface of the substrate to form a passivation film, thereby protecting the cleaning step. The substrate is exposed to the atmosphere and is extremely resistant to corrosion and has a certain degree of corrosion resistance.

However, the cleaning step causes the surface of the substrate to lose its original metallic luster, and is dimmed, and the passivation film is also transparent and cannot beautify the appearance. Therefore, a colored coating step, that is, coating on the passivation film, is required. Covering a colored paint to completely cover the dull appearance of the substrate, and at the same time utilizing the color distribution of the formed colored paint film and the thick feel of the paint to meet the consumer's visual preferences, and The corrosion resistance of the substrate is further enhanced.

The above surface treatment method has the disadvantages that the operation process is complicated, a large amount of water and organic solvent are consumed, and a colored paint must be used to cover the magnesium-containing substrate which is light in color after the cleaning step, thereby reducing the manufacturer's follow-up The design of the casing or bracket, and the flexibility of the positioning plan of the commodity marketing market. In addition, the surface treatment method does not compensate for the fine dents and minute cracks on the surface of the magnesium-containing substrate which are inadvertently caused by the mold.

There are also many consumers who think that the metal texture and luster of the outer casing have a futuristic, high-grade, and fashionable sense, and they have a special liking for it; in order to make the equipment made of the magnesium-containing substrate The frame or the product casing meets the needs of such consumers. A common preparation method is to form the passivation film on the magnesium-containing substrate, and then plate the multi-layered metal on the passivation film by electroplating. A laminate formed by, for example, copper, nickel, chromium, etc.; however, this method consumes a large amount of electrical energy and causes heavy metal contamination, and in particular, chromium may be derived from carcinogenic Cr ⁶⁺ ions. Therefore, the conventional method is costly and inconsistent with environmental protection requirements, and the metal plated in the laminate is not easily separated, thereby increasing the difficulty in recovering various metals.

Obviously, what is needed in the art is a laminate comprising a layer of a magnesium-containing substrate and which simply emits a metallic luster, thereby facilitating the manufacturer to more flexibly plan the design of the related product and create a huge Commercial interests; and there is also a need in the art for an easy operation, less water and organic solvents, environmental compliance, corrosion protection of the magnesium-containing substrate, and metal surface of the magnesium-containing substrate. A surface treatment method for a glossy magnesium-containing substrate.

Accordingly, a first object of the present invention is to provide a method of treating a surface of a magnesium-containing substrate which achieves the above-described various objectives, comprising a polishing step, and a modifying step or a coating step.

The polishing step is to contact a magnesium-containing substrate with a polishing liquid composed of a solid portion and a liquid portion, and polish the substrate, after the solid portion of the polishing liquid is removed from the surface of the substrate, Drying the retained liquid portion and forming a coating film on the surface of the substrate; wherein the solid portion of the polishing liquid includes a plurality of abrasive particles, and the liquid portion includes a strong base and an aromatic compound , a wrong mixture, a source of monophosphate, and a first solvent.

The upgrading step and the coating step are basically alternatively, or the upgrading step and the coating step are sequentially performed. The modifying step is: drying a modified liquid with a coating film formed on the surface of the magnesium-containing substrate, and drying the coating film, so that the coating film is modified to include a body attached to the surface of the substrate. a region, and a modified region that is attached to the surface of the substrate away from the surface of the substrate; the coating step is to apply a coating liquid or a paint to the coating film to make the coating film The coating liquid on the surface is dried to form a coating film on the coating film. Wherein, the modified liquid comprises a titanium source, a vanadium source, an acid source, a neutralizing agent, and a second solvent, and the coating liquid comprises a coating resin and a coating additive.

The above-described method of the present invention may be carried out by a modification step or a coating step, or even successively, and the respective laminates as the second to fourth objects of the present invention are obtained correspondingly. The laminates each substantially comprise a magnesium-containing substrate layer and a coating layer formed on the magnesium-containing substrate layer, or selectively applied by the coating step, and further comprising a film formed thereon Coating layer on the coating layer, or selectively using the modifying step to include the body layer formed on the magnesium-containing substrate layer and away from the magnesium-containing substrate layer Forming a modified region on the body region.

The fifth and sixth objects of the present invention are to provide a polishing liquid and a coating liquid, respectively, which can be applied to the method for carrying out the above first object of the present invention, and the formed coating film and coating The film is also transparent to allow the metallic luster of the magnesium-containing substrate to penetrate.

In addition to obtaining anti-corrosion protection of the treated magnesium-containing substrate, the surface treatment method of the invention has many advantages, such as the operation step is very simple and the implementation is extremely flexible, the required water consumption is small, and the water resource can be saved. The use of cadmium does not cause a large amount of waste water or heavy metal contamination, and the magnesium-containing substrate in the obtained laminate is also easily recovered, thereby highly complying with environmental demands; on the other hand, the magnesium-containing group after the polishing step The material, except for the tiny depressions and micro-cracks thereon, can be modified or repaired by the liquid portion of the polishing liquid, and the film layers of the obtained laminate are transparent and thin, so the magnesium-containing group at the bottom layer is The metallic luster of the material is exuded, giving the laminate a metallic feel.

Alternatively, the coating step can be carried out using a general paint in the art, or using the coating liquid of the present invention; and the coating liquid can be selectively formulated to be water-based or oily, depending on the type of material used, The surface of the coating film formed by the special coating liquid can be formed by forming a coating film which is excellent in moisture resistance, hardness, abrasion resistance, and water and dirt. In addition to maintaining cleanliness for a long time, it can also provide better isolation and protection for the magnesium-containing substrate covered.

Based on the foregoing essential elements of the various objects of the present invention and the benefits obtained, the embodiments thereof will be further described herein and the available materials or secondary operating conditions will be exemplified.

The surface treatment method of the magnesium-containing substrate of the present invention may include, in addition to the polishing step, and the modification step or the coating step which is basically performed after the polishing step, the method of the present invention may also include The polishing step, the upgrading step, and the coating step are performed sequentially; the implementation procedures of the respective steps are as described above. The method is applicable to magnesium-containing substrates of various materials, and magnesium substrates commonly used in the art, such as AZ914D, AM60, AM50, AEx-3, AE44, etc., are also applicable to the present application.

The polishing liquid of the present invention used in the polishing step is composed of a solid portion including a plurality of abrasive particles, and the liquid portion includes a strong base, an aromatic compound, and a wrong portion. Mixture, a source of monophosphate, and a first solvent.

In the polishing liquid of the present invention, the solid portion may occupy a larger proportion in the polishing liquid relative to the liquid portion thereof, and preferably, the solid portion accounts for between 50% and 99.9% by weight of the polishing liquid; more preferably The ground is between 80% and 98% by weight; most preferably between 90% and 95% by weight. In addition, the solid portion can be recycled and reused, so that in the case of the polishing liquid, the consumable has only its liquid portion, and it can only occupy a small amount, thereby effectively saving the material cost of the manufacturer and avoiding A large amount of wastewater is generally caused by disposal after use.

For such abrasive particles, the material may be selected from cerium oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), hard resin [such as epoxy resin, polyacrylic acid derivative resin, etc.] And commonly used ceramic materials [such as zirconium oxide, titanium oxide, tantalum oxide, etc.]; it is also possible to mix abrasive particles of different materials as described above. It is also suggested that the particle size of the abrasive particles is between 2 mm and 15 mm.

For the liquid portion, it is recommended that the strong base be selected from potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), calcium hydroxide [Ca(OH) ₂ ], and barium hydroxide [ Ba(OH) ₂ ], or a combination of these; wherein the preferred strong base is selected from NaOH, KOH, or a combination thereof. It is further suggested that the content of the strong base in the liquid portion is between 0.1% and 50% by weight, preferably between 1% and 15% by weight.

It is recommended that the aromatic compound be, for example, an aromatic phenol derivative (particularly an aromatic phenol compound), an aromatic heterocyclic derivative, or a combination thereof. The phenolic compound has a benzene ring in addition to its aromaticity, and is bonded to the benzene ring, and at least one selected from -OH, -NH ₂ , -SH, -NO ₂ , -COOH, etc. a functional group; preferably the phenolic compound is selected from the group consisting of salicylic acid, catechol, hydroquinone, resorcinol, nitrophenol, aminophenol, methylphenol, methylbenzene Phenol, or a combination of these; more preferably from salicylic acid, catechol, nitroaniline, or a combination thereof. It is further proposed that the content of the aromatic compound in the liquid portion is between 0.1% by weight and 20% by weight, preferably between 0.5% and 5% by weight.

It is suggested that the wrong agent can be selected from oxalic acid, citric acid, tartaric acid, gluconic acid, maleic acid, phthalic acid, monoethanolamine, triethanolamine, ethylenediamine, melamine, ethylenediaminetetraacetic acid (EDTA), or the like. One combination; preferably selected from EDTA, ethylenediamine, melamine, or a combination of these. It is further suggested that in the liquid portion, the content of the binder is between 0.1% and 20% by weight, preferably between 0.5% and 5% by weight.

It is recommended that the phosphate source be selected from phosphoric acid, phosphate, phosphorous acid, phosphite, hypophosphorous acid, hypophosphite, pyrophosphoric acid, pyrophosphate, polyphosphoric acid, polyphosphate, metaphosphoric acid, metaphosphate, monophosphoric acid. An ester, a phosphite, or a combination thereof; preferably selected from the group consisting of pyrophosphoric acid, phosphoric acid, phosphorous acid, or a combination thereof. It is further proposed that the content of the phosphate source in the liquid portion is between 0.1% by weight and 20% by weight, preferably between 0.5% and 5% by weight.

In addition to the various essential components described above, the solid portion of the polishing liquid of the present invention may further comprise a polishing accelerator which enhances the grinding effect, which is selected from alumina powder, zirconia powder, cerium oxide powder, or the like. One of the combinations; substantially the same as the above-mentioned abrasive particles, the polishing accelerator selected is higher in hardness, or smaller in particle size, it is recommended that the particle size of the polishing accelerator is between 0.5 μm and 500 μm. . It is further suggested that the content of the grinding accelerator in the solid portion is between 0.01% by weight and 10% by weight, preferably between 0.05% and 1% by weight.

Further, the liquid portion of the polishing liquid of the present invention may further comprise a resist selected from a manganate source, a vanadate source, a stannate source, or a combination thereof; the resist is by the same The protective effect of the coating film formed on the specific magnesium-containing substrate is more excellent than the acid group contained.

With regard to the pH of the polishing liquid, it is recommended to exceed 10 or even more than 14 (i.e., [OH ^- ] > 1M therein); preferably, the pH is between 10 and 14.

The operating temperature of each step is not limited, and can be operated under normal room temperature (for example, 15 ° C to 35 ° C); however, the liquid portion, the modifying liquid, the paint, or the drying liquid of the polishing liquid is dried. In the case of the coating liquid, the operator selects a suitable temperature range by visualizing the demand or the liquid component to be dried.

It is further proposed that when the polishing liquid is contacted with the magnesium-containing substrate, a vibration frequency of 5 Hz to 200 Hz may be applied to the polishing liquid to enhance the grinding effect and promote the liquid state in the polishing liquid. The reaction between the part and the surface of the substrate. When the polishing liquid is in contact with the magnesium-containing substrate, the liquid portion thereof is naturally adhered to the surface of the substrate, and the solid portion can be made from the substrate by slightly rinsing with water before drying the liquid portion. The surface is removed, and then the liquid portion on the surface of the substrate is dried to obtain a drape film formed on the surface of the substrate, that is, the grinding step is completed. Thereafter, the operator may select the modification step or the coating step according to the needs (for example, the type of the magnesium-containing substrate used), or sequentially perform the upgrading step and the coating step; other factors are temporarily not considered. If all three steps are carried out, the corrosion-resistant protection of the magnesium-containing substrate layer in the obtained laminate is naturally the most stringent.

The modifying step is to contact a modified liquid with the coating film formed on the surface of the magnesium-containing substrate by the polishing step, and drying the modified liquid on the coating film, thereby making the coating liquid The coating is modified to include a body region that is coupled to the surface of the substrate, and a modified region that is coupled to the surface of the substrate, and the modified liquid comprises a titanium source. A vanadium source, an acid source, a neutralizing agent, and a second solvent.

The titanium source is used to provide titanium ions, which can be selected from titanium trichloride [TiCl ₃ ], titanium tetrachloride [TiCl ₄ ], titanyl sulfate [TiOSO ₄ ], tetraethoxy titanium [Ti (OEt) ₄ ], tetraisopropyl titanate [Ti(OiPr) ₄ ], titanium (III) sulfate [Ti ₂ (SO ₄ ) ₃ ], or a combination of these.

The vanadium source is used to provide vanadium ions, which can be selected from vanadium trichloride [VCl ₃ ], vanadium pentoxide [V ₂ O ₅ ], vanadium oxychloride (V) [VOCl ₃ ], vanadyl sulfate [ VOSO ₄ 】, ammonium metavanadate [NH ₄ VO ₃ ], vanadium oxyfluoride (V) [VOF ₃ ], or a combination of these.

Preferably, the acid source is selected from the central atom of the acid radical provided by the acid atom, and the oxidizing amount is not saturated with, for example, nitrous acid, nitrite, or a sulfide containing sulfur having an oxidation state of less than +6. Phosphorous acid, phosphite, oxalic acid, oxalate, tartaric acid, tartrate, hypophosphorous acid, hypophosphite, or a combination of these. When the modified region of the drape film is formed, the oxidation atom derived from the acid source source does not reach the saturated central atom, and the corrosive factor that is contacted may be contacted before the magnesium-containing substrate covered thereby For example, water or air acts, and the coating film is made denser by oxygen filling, thereby providing better protection to the magnesium-containing substrate covered thereby, and avoiding corrosion of the substrate.

The neutralizing agent is an alkali, and the pH of the modifying liquid can be appropriately adjusted, whereby the coating film is modified at a more appropriate speed to obtain a better quality.

The second solvent is used to dissolve or disperse the substance in the reforming liquid, for example, the above-mentioned titanium source, vanadium source, acid source, neutralizing agent, etc., so there is no particular limitation on the kind of the second solvent; Based on considerations of cost and ease of formulation, it is recommended that the second solvent be water.

The coating step can be carried out by a coating liquid of the invention or a paint; the paint can be, for example, a colored paint used in a colored coating step of a conventional surface treatment method, or transparent Paint, or the coating liquid of the present invention.

The coating liquid of the present invention has no particular limitation on the kind of the coating resin contained therein, and an optional water-based PU resin (for example, an aqueous PU resin of the type "WPC350", produced by Warburg Resin Co., Ltd.), Or epoxy resin (for example, epoxy resin of the type "WP829", produced by Warburg Resin Co., Ltd.) and other commercially available coating resin products; the properties of the coating resin will relatively coat the present invention. The liquid is water or oily.

The coating additive is dissolved in the coating resin, and is used for the purpose of enhancing the adhesion between the coating film and the coating film, and the surface hydrophobicity of the coating film. It is recommended that the coating additive be selected from a polyol alkane compound (for example, polyethylene glycol, trimethylolpropane, or a combination thereof), a polyol ether compound (such as a glycol ether), a polyolene compound ( For example, polyacrylic alcohol), a polyhydric alcohol amine compound, a polyphenolic compound (meaning that at least two OH groups are attached to a benzene ring moiety in its structure), a melamine, an isocyanide derivative, or a combination thereof. Wherein, the polyol amine compound is, for example, triethanolamine, diethanolamine, or a combination thereof; and the polyphenol compound is, for example, catechol, resorcinol, hydroquinone, 1, 2, 4 Pyrogallol, 1,3,5 benzenetriol, or a combination of these; isocyanide derivatives are often used as crosslinkers in the polymer field, which are isocyanide compounds which can have various substituents. Different isocyanamide derivatives can also be used in combination. Preferably, the coating additive is selected from the group consisting of trimethylolpropane, catechol, isocyanide derivatives, or a combination thereof.

If necessary, the coating liquid may further contain a diluent to reduce the viscosity of the coating liquid and to be more convenient to use. The choice of the type of the diluent depends on the nature of the coating resin; when the aqueous resin is selected, water can be used as a diluent, and if an epoxy resin is used, the aprotic solvent is relatively It is a ketone solvent) is the diluent. The diluent is selected from the group consisting of water, alcohol, isopropanol, butanol, acetone, 2-butanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, diacetone alcohol, or the like. a combination of one.

In addition, the coating liquid may further contain a hardness improving agent such as water glass, phthalic acid gel or aluminum hydroxide to increase the hardness of the coating film, and the materials may also be used in combination.

In addition, the coating liquid of the present invention may further contain a coloring material; and if the coating liquid of the present invention is water-based, it may also contain a wetting agent, which has the effect of reducing the cohesive force of the coating liquid to make it more uniform. It is adhered to the coating film and improves the adhesion between the coating film and the coating film. The above-mentioned diluents, hardness improvers, colorants, humectants and the like which can be selectively added can also be used in combination, and such materials have been widely used in related fields, and can be generally used in the art. The knowledge person can handle the type and amount of materials to be used, so the relevant details will not be described here.

The coating additive is used to make the coating resin exert better performance, and is blended with it to form the coating liquid of the present invention; it is also practically found that the coating additive can be even at a very small content (for example, less than 0.1% by weight). Can be effective. In the coating liquid of the present invention, the coating additive may also be between 0.1% by weight and 5% by weight, or further between 0.5% and 2% by weight.

It is suggested that the pH of the coating liquid of the present invention is between 5 and 11 to facilitate reaction with the coating film to form the coating film, thereby providing better corrosion protection to the underlying magnesium-containing substrate. Preferably, the pH of the coating liquid is between 7 and 11, more preferably between 8 and 10.

It is worth noting that the solvents in general paints are mostly organic, which have a negligible negative impact on the physiology of the operator and the overall environment. However, the paints can be relied on by the surface tension of the organic solvent. A coating film having a uniform thickness is formed; in other words, a coating film prepared by using an aqueous solvent is not easily applied uniformly, and the formed coating film often has uneven thickness, wrinkles on the surface, and the like. Many shortcomings.

However, the aqueous coating liquid of the present invention (especially formulated with an aqueous PU resin and an aqueous solvent) does not have the above disadvantages under the action of the coating additive, and the coating liquid is easily coated by the coating. A small gap in the surface of the membrane penetrates into it, so that the coating film formed after drying can be more tightly bonded to the coating film.

The coating liquid should be chemically reacted when it comes into contact with the coating film, so that after the coating liquid is dried, the surface of the coating film formed will be hydrophobic, and it is not easy to adhere to moisture and other dirt, and More thoroughly, the factors that cause corrosion of the magnesium-containing substrate are isolated, thereby providing more complete protection of the magnesium-containing substrate.

By the surface treatment method of the magnesium-containing substrate of the present invention, the obtained laminate can not only emit metal luster by simply covering the magnesium-containing substrate layer therein, but also cover the substrate layer. The coating film can also provide sufficient corrosion protection to the underlying magnesium alloy substrate after the modification step and/or the formation of a coating film thereon. [Neutral salt spray] Test, abbreviated as "NSST"), can last for at least 72 hours or more.

In summary, the surface treatment method of the magnesium-containing substrate of the present invention can effectively remove the surface of a magnesium-containing substrate, in addition to being extremely simple in operation, and the consumption of materials and solvents is extremely small, thereby greatly reducing the possibility of contamination. The impurities such as grease and oxide, and the micro-depressions and micro-cracks caused by the mold on the surface of the magnesium-containing substrate are modified, and the treated magnesium-containing substrate can further emit metallic luster.

In addition, the coating film formed on the surface of the substrate and the coating film selectively formed on the coating film can not only transmit the metallic luster of the magnesium-containing substrate underneath, etc., The substrate can also be provided with anti-corrosion protection, so that the laminate which is long-established in the art by the magnesium-containing substrate to exhibit a metallic texture can be obtained by the method of the present invention, and can be maintained under long-term storage. Its shiny metal texture. The coating film formed by the coating liquid of the present invention can also have good moisture resistance, hardness, and abrasion resistance, and it has a tendency to cause corrosion of the magnesium-containing substrate by moisture, moisture, or the like. The excellent isolation ability, so that the surface of the coating film can not only maintain cleanliness for a long time, but also provides better protection to the magnesium-containing substrate, so that it has more excellent corrosion resistance.

Therefore, the method of the present invention not only breaks through many limitations of the surface treatment methods of the magnesium-containing substrate and various magnesium-containing substrates, but also enables the manufacturer to have more flexibility in the design of the product to conform to various forms on the market. Needs and expectations. Obviously, all the objects proposed by the present invention provide a good solution to the long-term technical bottleneck in the field.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

Claims (29)

A surface treatment method for a magnesium-containing substrate, comprising: a polishing step of contacting a magnesium-containing substrate with a polishing liquid composed of a solid portion and a liquid portion, and the polishing liquid is applied with a 5 Hz to 200 Hz a frequency of vibration, and polishing the substrate, after the solid portion of the polishing liquid is removed from the surface of the substrate, drying the liquid portion retained and forming a coating film on the surface of the substrate; The solid portion of the polishing liquid includes a plurality of abrasive particles, and the liquid portion includes a strong base, an aromatic compound, a binder, a phosphate source, and a first solvent; and a upgrading step or a a coating step of drying a modified liquid in contact with a coating film formed on the surface of the magnesium-containing substrate, whereby the coating film is modified to include an interface to the substrate a surface region on the surface, and a modified region that is attached to the surface of the substrate away from the surface of the substrate; the coating step is to contact a coating liquid or a paint to the coating film, so that The coating liquid on the coating film is dried on the coating film Forming a coating film; wherein the modifying liquid comprises a titanium source, a vanadium source, an acid source, a neutralizing agent, and a second solvent, and the coating liquid comprises a coating resin, and A coating additive. The surface treatment method of the magnesium-containing substrate according to the first aspect of the patent application is the step of including the polishing step and the subsequent coating step. A surface treatment method for a magnesium-containing substrate according to claim 1 of the patent application, comprising the polishing step, and the subsequent modification step. The surface treatment method of the magnesium-containing substrate according to claim 3 of the patent application further includes the coating step after the upgrading step. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the solid portion of the polishing liquid is between 50% and 99.9% by weight of the polishing liquid. The surface treatment method of the magnesium-containing substrate according to the first aspect of the invention, wherein the material of the abrasive particles in the polishing liquid is selected from the group consisting of cerium oxide, aluminum oxide, hard resin, ceramic material, or One of these combinations. The surface treatment method for a magnesium-containing substrate according to the first aspect of the invention, wherein the particle size of the abrasive particles in the polishing liquid is between 2 mm and 15 mm. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the strong base in the polishing liquid is selected from potassium hydroxide, sodium hydroxide, lithium hydroxide, calcium hydroxide, and hydroxide. Oh, or a combination of these. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the strong base accounts for 0.1% by weight to 50% by weight of the liquid portion of the polishing liquid. The surface treatment method for a magnesium-containing substrate according to the first aspect of the invention, wherein the aromatic compound in the polishing liquid is an aromatic phenol derivative, an aromatic phenol compound, and aromatic a heterocyclic derivative, or a combination of these. The surface treatment method for a magnesium-containing substrate according to claim 10, wherein the phenolic compound is selected from the group consisting of salicylic acid, catechol, hydroquinone, resorcin, and nitro Phenol, aminophenol, methylphenol, methylbenzenediol, or a combination of these. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the aromatic compound is between 0.1% by weight and 20% by weight based on the liquid portion of the polishing liquid. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the crosslinking agent in the polishing solution is selected from the group consisting of oxalic acid, citric acid, tartaric acid, gluconic acid, maleic acid, and phthalic acid. Monoethanolamine, triethanolamine, ethylenediamine, melamine, ethylenediaminetetraacetic acid, or a combination thereof. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the crosslinking agent is between 0.1% by weight and 20% by weight of the liquid portion of the polishing liquid. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the phosphate source in the polishing solution is selected from the group consisting of phosphoric acid, phosphate, phosphorous acid, phosphite, hypophosphorous acid, and hypophosphite. , pyrophosphoric acid, pyrophosphate, polyphosphoric acid, polyphosphate, metaphosphoric acid, metaphosphate, monophosphate, phosphite, or a combination of these. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the phosphate source is between 0.1% by weight and 20% by weight of the liquid portion of the polishing liquid. Surface treatment method of the magnesium-containing substrate according to claim 1 of the patent application scope The method wherein the solid portion of the polishing liquid further comprises a grinding accelerator selected from the group consisting of alumina powder, zirconia powder, cerium oxide powder, or a combination thereof. The surface treatment method for a magnesium-containing substrate according to claim 17, wherein the particle size of the polishing accelerator is between 0.5 μm and 500 μm. The surface treatment method for a magnesium-containing substrate according to claim 17, wherein the polishing accelerator is between 0.01% by weight and 10% by weight of the solid portion of the polishing liquid. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the liquid portion of the polishing liquid further comprises a resist selected from the group consisting of a manganate source, a vanadate source, and a stannate source. , or a combination of these. A surface treatment method for a magnesium-containing substrate according to claim 1, wherein the polishing liquid has a pH of more than 10. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the paint used in the coating step is a colored paint or a transparent paint. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the coating resin used in the coating liquid of the coating step is selected from an aqueous PU resin or an epoxy resin. . The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the coating additive of the coating liquid is selected from the group consisting of a polyol alkyl compound, a polyol ether compound, and a polyol alkyl compound. Polyolamine a compound, a polyphenolic compound, a melamine, an isocyanide derivative, or a combination thereof. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the coating liquid further comprises a diluent, a hardness improving agent, a coloring material, a wetting agent, or a combination thereof. The surface treatment method for a magnesium-containing substrate according to claim 25, wherein the diluent is selected from the group consisting of water, alcohol, isopropanol, butanol, acetone, 2-butanone, and methyl isobutylate. Ketone, ethyl acetate, butyl acetate, diacetone alcohol, or a miscible combination thereof. The surface treatment method for a magnesium-containing substrate according to claim 25, wherein the hardness enhancer is selected from the group consisting of water glass, phthalic acid glue, aluminum hydroxide, or a combination thereof. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the coating additive is between 0.1% by weight and 5% by weight of the coating liquid. The surface treatment method for a magnesium-containing substrate according to claim 1, wherein the coating liquid has a pH of between 5 and 11.