阅读说明：本技术 一种渗锌方法以及防腐蚀金属件 (Zinc impregnation method and anti-corrosion metal part ) 是由 乐林江 沈伟 乐政 于 2020-08-11 设计创作，主要内容包括：本申请提供一种渗锌方法及防腐蚀金属件。其中,渗锌方法包括：S1、对待渗锌的金属件进行除油除锈处理,并将处理后的金属件与渗锌剂共同置于密闭渗罐中,所述渗锌剂包括以下质量份数的组分：金属粉末20-100份,分散剂40-80份,分解剂0.2-5份,其中,所述金属粉末包括锌粉60-97份和镁粉3-40份；S2、驱赶所述密闭渗罐中的空气,并关闭所述密闭渗罐的阀门；S3、对所述密闭渗罐进行升温处理,升温至预设温度后通入氢气加压,直至达到预设氢气压力条件,保温1-10小时,金属件表面形成渗层,完成渗锌。本申请提供的渗锌方法,操作简单,使用方便,成本低廉,经济效益高,适用范围广。(The application provides a zincizing method and an anti-corrosion metal piece. The zinc impregnation method comprises the following steps: s1, performing oil and rust removal treatment on the metal piece to be subjected to zinc impregnation, and placing the treated metal piece and a zinc impregnation agent into a closed impregnation tank together, wherein the zinc impregnation agent comprises the following components in parts by weight: 20-100 parts of metal powder, 40-80 parts of dispersing agent and 0.2-5 parts of decomposing agent, wherein the metal powder comprises 60-97 parts of zinc powder and 3-40 parts of magnesium powder; s2, driving the air in the closed infiltration tank, and closing a valve of the closed infiltration tank; and S3, heating the sealed infiltration tank, introducing hydrogen to pressurize after heating to a preset temperature until reaching a preset hydrogen pressure condition, preserving heat for 1-10 hours to form an infiltration layer on the surface of the metal piece, and completing zinc infiltration. The zinc impregnation method is simple to operate, convenient to use, low in cost, high in economic benefit and wide in application range.)

1. A zincating method, comprising:

s1, performing oil and rust removal treatment on the metal piece to be subjected to zinc impregnation, and placing the treated metal piece and a zinc impregnation agent into a closed impregnation tank together, wherein the zinc impregnation agent comprises the following components in parts by weight: 20-100 parts of metal powder, 40-80 parts of dispersing agent and 0.2-5 parts of decomposing agent, wherein the metal powder comprises 60-97 parts of zinc powder and 3-40 parts of magnesium powder;

s2, driving the air in the closed infiltration tank, and closing a valve of the closed infiltration tank;

and S3, heating the sealed infiltration tank, introducing hydrogen to pressurize after heating to a preset temperature until reaching a preset hydrogen pressure condition, preserving heat for 1-10 hours to form an infiltration layer on the surface of the metal piece, and completing zinc infiltration.

2. The zincating method according to claim 1, wherein the preset hydrogen pressure condition is determined as a hydrogen pressure not lower than one atmosphere based on an equilibrium constant of the reduction reaction by diffusion of magnesium to the zincated layer in S3;

preferably, the reduction reaction generated by the diffusion of the magnesium powder to the infiltrated layer has the equation:

the equilibrium constants for the reduction reaction are:

wherein, in

based on lgK_{p, reduction of}Determining that the hydrogen pressure is not less than one atmosphere pressure;

more preferably, in S3, the closed infiltration tank is heated to 360-415 ℃ or 320-480 ℃, then hydrogen is introduced for pressurization until the hydrogen pressure is not lower than one atmosphere, and heat preservation is carried out for 1-10 hours, so that an infiltration layer is formed on the surface of the metal piece, and zinc infiltration is completed.

3. The zincating method according to claim 1, wherein the magnesium powder is pure magnesium powder or magnesium alloy powder;

preferably, the magnesium powder is pure magnesium powder with the purity of more than 95% or magnesium alloy powder with the weight ratio of magnesium not less than 40%.

4. The zincating method according to claim 1, wherein the dispersant is ceramic powder, and the decomposer is ammonium halide;

preferably, the ceramic powder comprises at least one of alumina, silica, magnesia, aluminum nitride, silicon carbide;

more preferably, the ammonium halide includes at least one of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium bromide, ammonium hydrogen fluoride.

5. The zincating method according to claim 1, wherein the zincating agent further comprises 0.5 to 3 parts of an active agent capable of promoting the penetration of magnesium into the cementation layer;

preferably, the active agent is a magnesium halide.

6. The zincizing method according to claim 1, wherein the particle size of the magnesium powder is 10 μm to 500 μm, the particle size of the zinc powder is 1 μm to 200 μm, and the particle size of the dispersant is 5 μm to 500 μm.

7. The zincating method according to claim 1, wherein the zincating agent further comprises manganese dioxide, and the mass part of the manganese dioxide is not more than the mass part of the decomposer.

8. The zincizing method according to claim 1, wherein in S2, the closed infiltration tank is vacuumized, or a protective atmosphere is introduced into the closed infiltration tank to drive air in the closed infiltration tank, and a valve of the closed infiltration tank is closed.

9. An anti-corrosion metal part characterized in that a percolated layer of the anti-corrosion metal part is made by the method according to claims 1-8.

10. The anti-corrosion metal article of claim 9 wherein the average magnesium content of the infiltrated layer is from 0.5 wt.% to 20 wt.%;

preferably, the thickness of the infiltrated layer is 5 μm to 200 μm.

Technical Field

The application relates to the technical field of chemical heat treatment of metal material surfaces, in particular to a zincizing method and an anti-corrosion metal piece.

Background

Zincing is a chemical heat treatment process for impregnating the surface of a metal material with zinc. The zinc impregnation treatment is carried out on the surface of the metal material, so that the atmospheric corrosion resistance of the metal material can be obviously improved. Among them, powder zincification is widely applied to the surface anticorrosion treatment of metal parts because of a series of advantages of no hydrogen embrittlement, high bonding strength, good corrosion resistance and the like. At present, most of global railway fasteners, high-strength fasteners and the like adopt a powder zinc impregnation anti-corrosion treatment method for surface protection.

The existing powder zinc impregnation technology still has the problem of low corrosion resistance. A cementation layer is formed on the metal piece after powder cementation of zinc on the metal piece is carried out by adopting a zincizing agent, the cementation layer formed by adopting the zincizing agent in the current market for cementation of zinc is mainly a zinc-iron alloy phase and a zinc phase, the crystal structure of zinc is an anisotropic close-packed hexagonal structure, and lattice constants are represented by a and c. During the zincizing process, the growth of zinc has orientation, the zinc preferentially grows along the c-axis direction, and the self-diffusion coefficient of the zinc is nearly 20 times of that of the zinc in the direction parallel to the c-axis and in the direction perpendicular to the c-axis. And because the existence of anisotropy, the grain boundary between the zinc crystals is a weak grain boundary structure in the growth process, and in the corrosion process, the weak grain boundary structure is transparent to corrosive substances such as chloride ions, and the corrosive substances can directly penetrate through the grain boundary of zinc to enter a steel matrix, so that red rusty spots can appear on the surface of a seeping layer quickly, and the time when the red rusty appears on the surface can be generally judged as the salt spray corrosion resistance life in a salt spray performance test. The service life of the common permeable layer salt mist resistance is only dozens of hours, and the requirement of the engineering salt mist resistance for hundreds of hours or even thousands of hours can not be met. This requires surface sealing, Dacromet coating, etc. after powder zincing to advance the overall corrosion resistance. However, most of the surface sealing and dacromet are organic or inorganic coatings, and under the conditions of wind sand, erosion and the like in the actual use environment, the sealing layer is easily worn away, so that premature corrosion often occurs, and the metal part is prematurely failed.

At present, the prior art mainly realizes the improvement of the corrosion resistance of a zincification layer by adding methods such as aluminum, nickel, rare earth and the like, but the methods are still limited to the improvement of the corrosion resistance of the zincification layer in practical application, and a patent named as a zinc-nickel cementation layer ferrous metal corrosion prevention process discloses a component of the zinc-nickel cementation layer and a powder cementation process, wherein the content of nickel powder is 0.5 wt% -1.4 wt%, but when the powder cementation treatment is carried out at the temperature of 500 ℃, nickel is difficult to infiltrate to form a cementation layer, so that a cementation layer with high corrosion resistance is difficult to form, the corrosion resistance of the cementation layer is basically equivalent to that of the traditional powder zincification, and the effect of improving the corrosion resistance of the cementation layer is not achieved.

The magnesium is very active chemically and can react with O₂、N₂、H₂Many non-metallic substances such as O and the like react, and the dosage is very difficult to control. Because of the special chemical property of magnesium, magnesium powder is rarely added into the zincizing agent in the prior art, even if the zincizing agent contains magnesium powder components, the dosage of the magnesium powder components is very small, the main effect is not realized by the magnesium powder, and the magnesium powder components are usually required to be matched with various other components for use. For example, a patent entitled "a highly active, fast-penetrating agent" discloses a highly active, fast-penetrating agent in which aluminum and magnesium are added to improve the activity of the penetrating agent and thus the fast-penetrating speed, and also does not achieve the effect of improving the corrosion resistance of the penetrated layer.

In addition, the magnesium powder added into the existing zinc impregnation agent generally has the particle size of below 10 μm, and the content of the magnesium powder in the metal powder is less than 5%. The purpose of adding magnesium powder into the existing zincizing agent is to clean the surface of a metal piece mostly through the high-temperature reaction of the magnesium powder, and the particle size and the content of the magnesium powder are enough to achieve the purpose. However, magnesium powder having a particle size of less than 10 μm, although it can clean surfaces, is easily exploded, has low safety, and reacts to form gaseous compounds under high temperature conditions. In the case where the content of magnesium powder in the metal powder is less than 5%, it reacts almost entirely with the metal surface under high temperature conditions, resulting in no or little penetration into the infiltrated layer.

More importantly, the metal is diffused and infiltrated into the infiltrated layer through the replacement reaction and the reduction reaction, and compared with the replacement reaction, the reaction activation energy required by the reduction reaction is lower and the reaction is easier to perform. Magnesium is an element with large atomic diameter, and is almost impossible to perform a displacement reaction with iron, and the displacement reaction with zinc requires high reaction activation energy, and the reaction is difficult to occur or slow to perform.

Therefore, it has been an unsolved problem whether magnesium can be used for the zincizing treatment, how it can be used for the zincizing treatment, and whether it can have a certain effect for the zincizing treatment.

Disclosure of Invention

In view of the above, embodiments of the present application provide a zincizing method and an anti-corrosion metal part to solve the technical defects in the prior art.

The application provides a zincizing method, which comprises the following steps:

s1, performing oil and rust removal treatment on the metal piece to be subjected to zinc impregnation, and placing the treated metal piece and a zinc impregnation agent into a closed impregnation tank together, wherein the zinc impregnation agent comprises the following components in parts by weight: 20-100 parts of metal powder, 40-80 parts of dispersing agent and 0.2-5 parts of decomposing agent, wherein the metal powder comprises 60-97 parts of zinc powder and 3-40 parts of magnesium powder;

s2, driving the air in the closed infiltration tank, and closing a valve of the closed infiltration tank;

and S3, heating the sealed infiltration tank, introducing hydrogen to pressurize after heating to a preset temperature until reaching a preset hydrogen pressure condition, preserving heat for 1-10 hours to form an infiltration layer on the surface of the metal piece, and completing zinc infiltration.

Further, in S3, the preset hydrogen pressure condition is determined to be not less than one atmosphere based on an equilibrium constant of the reduction reaction occurring upon diffusion of magnesium into the zincized layer.

Further, in S3, heating the sealed infiltration tank to 360-415 ℃ or 320-480 ℃, introducing hydrogen to pressurize until the hydrogen pressure is not lower than one atmosphere, and preserving heat for 1-10 hours to form an infiltration layer on the surface of the metal piece to finish zinc infiltration.

Further, the magnesium powder is pure magnesium powder or magnesium alloy powder;

preferably, the magnesium powder is pure magnesium powder with the purity of more than 95% or magnesium alloy powder with the weight ratio of magnesium not less than 40%.

Further, the dispersing agent is ceramic powder, and the decomposing agent is ammonium halide;

preferably, the ceramic powder comprises at least one of alumina, silica, magnesia, aluminum nitride, silicon carbide;

more preferably, the ammonium halide includes at least one of ammonium chloride, ammonium fluoride, ammonium iodide, ammonium bromide, ammonium hydrogen fluoride.

Furthermore, the zincizing agent also comprises 0.5 to 3 parts of an active agent capable of promoting the magnesium to permeate into the cementation layer;

preferably, the active agent is a magnesium halide.

Furthermore, the particle size of the magnesium powder is 10-500 μm, the particle size of the zinc powder is 1-200 μm, and the particle size of the dispersing agent is 5-500 μm.

Further, the zincizing agent also comprises manganese dioxide, and the mass part of the manganese dioxide is not more than that of the decomposer.

Further, in S2, the sealed infiltration tank is vacuumized, or a protective atmosphere is introduced into the sealed infiltration tank to drive air in the sealed infiltration tank, and a valve of the sealed infiltration tank is closed.

Further, the equation of the reduction reaction generated by the magnesium powder diffusing to the infiltrated layer is as follows:

the equilibrium constants for the reduction reaction are:

wherein, inIn the case of (2), the equilibrium constant of the reduction reaction is:

based on lgK_{p, reduction of}The hydrogen pressure is determined to be not less than one atmosphere ≧ -2.

The present application also provides a corrosion-resistant metal part whose percolated layer is made by the method as described above.

Further, the average content of magnesium in the seeping layer is 0.5 wt% -20 wt%;

preferably, the thickness of the infiltrated layer is 5 μm to 200 μm.

The zinc impregnation method provided by the application has the following technical effects:

firstly, the air in the closed infiltration tank is driven, and the magnesium has extremely high activity, so that the reaction of the magnesium in the zinc impregnation agent and the air can be effectively avoided.

The two-way process is to carry out heating treatment on the closed infiltration tank, so that not only can air in the closed infiltration tank be further driven, but also a suitable environmental condition for completing the zinc infiltration of the metal piece is created, after the temperature is raised to a preset temperature, hydrogen is adopted for pressurization until a preset hydrogen pressure condition is reached, the heat is preserved for 1-10 hours, and the zinc infiltration is completed, wherein the hydrogen is adopted for pressurization, on one hand, introduced hydrogen can react with oxygen to remove magnesium oxide on the metal piece, on the other hand, required atmosphere conditions and pressure conditions can be provided for reduction reaction generated by magnesium infiltration into the infiltration layer, the magnesium infiltration speed is improved, and the infiltration layer quality is enhanced.

Thirdly, the metal piece is subjected to zincizing treatment through a zincizing agent containing zinc powder and magnesium powder, because zinc has anisotropy, the crystal boundary between zinc crystals in the growth process is a weak crystal boundary structure which is transparent to corrosive substances such as chloride ions and the like, the corrosive substances can directly penetrate through the weak crystal boundary structure to corrode, magnesium can be gathered at the weak crystal boundary structure of zinc, and MgZn is formed through high-temperature reaction₂、Mg₂Zn₁₁And the like, so that a weak grain boundary structure is converted into a strong grain boundary structure which can effectively block corrosive substances such as chloride ions, and the corrosion resistance of a permeable layer can be greatly improved.

In a word, the zincizing method provided by the application is simple to operate, convenient to use, low in cost, high in economic benefit and wide in application range, and particularly adopts a magnesium-containing zincizing agent to zincize metal parts under the condition of hydrogen pressurization, so that the corrosion resistance of a permeable layer can be remarkably improved due to the addition of magnesium powder, the hydrogen pressurization can also provide assistance for magnesium infiltration, the magnesium is further promoted to rapidly and efficiently infiltrate the permeable layer, and the corrosion resistance of the permeable layer is greatly improved.

According to the anti-corrosion metal part, zinc and magnesium are infiltrated into the surface of the anti-corrosion metal part through the zinc infiltration method to form an infiltration layer capable of preventing the metal part from being corroded, and the magnesium and the zinc interact to form MgZn₂、Mg₂Zn₁₁And the like, so that a solid protective barrier is constructed for the metal part, corrosive substances such as chloride ions and the like are prevented from corroding the metal part, the corrosion resistance of the metal part is effectively improved, the service life of the metal part is prolonged, the cost is low, and the method is easy to popularize and use.

Drawings

FIG. 1 is a composition distribution diagram of a magnesium-containing zincated layer having an average magnesium content of 5 wt% on the surface of steel according to an embodiment of the present application;

FIG. 2 is a comparison of X-ray diffraction (XRD) phase structures of three different magnesium content percolates;

FIG. 3 is a surface state diagram of a magnesium-containing zincating layer subjected to salt spray corrosion for different periods of time according to an embodiment of the present application;

FIG. 4 is a cross-sectional view of a magnesium-containing zincating layer of one embodiment of the present application after 0 hours of salt spray etching;

FIG. 5 is a cross-sectional view of a magnesium-containing zincating layer of 1000 hours after salt spray etching in accordance with an embodiment of the present invention;

FIG. 6 is a schematic view showing a cross-sectional view of a magnesium-containing zincating layer after 2000 hours of salt spray corrosion according to an embodiment of the present invention;

FIG. 7 is a schematic view of a 4000 hour cross-sectional view of a magnesium-containing zincating layer in accordance with an embodiment of the present invention;

FIG. 8 is a surface view of a carburized layer with an average magnesium content of 43% for an example of the present application;

FIG. 9 is a cross-sectional profile of a carburized layer with an average magnesium content of 43% for an embodiment of the present application;

FIG. 10 is an enlarged view of corrosion products from the surface of a conventional zincized layer according to an embodiment of the present application;

fig. 11 is an enlarged view of corrosion products on the surface of a zinciferous layer containing magnesium of a corrosion-protected metallic article according to an embodiment of the present application.

Detailed Description

The following description of specific embodiments of the present application refers to the accompanying drawings.

In the present invention, unless otherwise specified, scientific and technical terms used herein have the meanings that are commonly understood by those skilled in the art. Also, the reagents, materials and procedures used herein are those that are widely used in the corresponding fields.