Preparation method of zinc-nickel alloy coating of automobile oil pipe metal joint

Abstract

The invention provides a preparation method of a zinc-nickel alloy coating of an automobile oil pipe metal joint. The preparation method comprises the steps of pretreatment, acid pickling, neutralization, electroplating, passivation, sealing and drying. The electroplating solution comprises the following components: 6 to 12 g / L of ZnO, 80 to 140 g / L of NaOH, 40 to 80 mL / L of a nickel complexing agent, 50 to 85 mL / L of a zinc complexing agent, 0.6 to 2 mL / L of a nickel supplement and 0.5 to 1 mL / L of a cylinder opening additive. The zinc-nickel alloy plating layer comprises 12.5%-15.5% of a nickel element and the balance of a zinc element; and the thickness of the zinc-nickel alloy plating layer is 8-12 microns. By optimizing the technological parameters of electroplating, the electroplating speed is increased, crystals are finer, the flexibility of a plating layer is improved, the phenomenon of poor powder falling is avoided during buckling and pressing, the corrosion resistance of the plating layer is improved, and the plating layer with the same thickness is free of red rust and black spots within 1000 hours in a salt spray test, and is improved by about 300 hours compared with a traditional plating layer.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc-nickel alloy electroplating, and in particular relates to a method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe. Background Art

[0002] Automobile oil pipes are mainly used in automobile steering systems, brake systems, air conditioning systems, etc.; the types of oil pipes mainly include high-pressure steel wire braided hoses, large-diameter high-pressure hoses, high-pressure steel wire spiral hoses, steel wire or fiber-reinforced nylon elastomer resin hoses, steel wire reinforced hoses, high-temperature resistant hoses, polyurethane hoses, etc.; the structure of automobile oil pipes mainly includes metal joints at both ends (usually non-stainless steel steel joints) and soft hoses in the middle; automobile oil pipes have many characteristics such as high pressure resistance and corrosion resistance. With the advancement of technology and economic development, the requirements for the corrosion resistance of metal joints of automobile oil pipes are getting higher and higher, and the corrosion resistance of existing metal joints of automobile oil pipes is increasingly unable to meet the current performance requirements.

[0003] Therefore, how to improve the corrosion resistance of metal joints in automobile oil pipes, and then improve the corrosion resistance and service life of the entire automobile oil pipe, is a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0004] The purpose of the invention is to provide a method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe comprises the following steps in sequence: pretreatment, pickling, neutralization, electroplating, passivation, sealing, and drying.

[0007] Preferably, the plating solution in the electroplating treatment contains the following components: 6-12 g / L ZnO, 80-140 g / L NaOH, 40-80 mL / L nickel complexing agent, 50-85 mL / L zinc complexing agent, 0.6-2 mL / L nickel supplementer, and 0.5-1 mL / L cylinder opening additive.

[0008] Preferably, the zinc-nickel alloy coating comprises the following elements in percentage by mass: 12.5% ​​to 15.5% nickel element and the balance zinc element;

[0009] The thickness of the zinc-nickel alloy coating is 8 micrometers to 12 micrometers.

[0010] Preferably, the electroplating treatment includes a primary electroplating of zinc-nickel alloy and a secondary electroplating of zinc-nickel alloy, and the thickness of the primary electroplating zinc-nickel alloy coating is 1 / 4-1 / 3 of the total thickness of the zinc-nickel alloy coating, and the thickness of the secondary electroplating zinc-nickel alloy coating is 2 / 3-3 / 4 of the total thickness of the zinc-nickel alloy coating;

[0011] A gas pressure sintering treatment is also included between the primary electroplating zinc-nickel alloy and the secondary electroplating zinc-nickel alloy, specifically: the metal joint with the primary electroplating zinc-nickel alloy coating is placed in a gas pressure sintering furnace, and then the gas pressure sintering furnace is evacuated to 0.1-10Pa, and then argon is filled into the gas pressure sintering furnace, and the pressure of the argon in the gas pressure sintering furnace is controlled to be 5-20MPa, and then the gas pressure sintering furnace starts to heat up, and the temperature is raised to 425℃-600℃ to perform heat preservation sintering treatment on the metal joint with the primary electroplating zinc-nickel alloy coating, and the gas pressure sintering heat preservation time is 5-15min, and then the high-temperature argon in the gas pressure sintering furnace is subjected to inter-wall heat exchange cooling treatment until the argon temperature in the furnace is reduced to 25℃-50℃, and then the argon in the furnace is discharged, and then the furnace is opened to take out the parts;

[0012] During the gas pressure sintering process, the zinc element in the primary electroplated zinc-nickel alloy coating melts and turns into zinc liquid, so that the pores between the particles in the primary electroplated zinc-nickel alloy coating disappear, the high pressure of the argon gas presses the molten zinc liquid tightly against the surface of the metal joint, so that there is no gap between the primary electroplated zinc-nickel alloy coating and the surface of the metal joint, the high pressure of the argon gas presses the molten zinc liquid to penetrate into the surface layer of the metal joint, so that the zinc liquid reacts with the iron element in the metal joint to form a zinc-iron alloy transition layer, and then the zinc liquid cools and solidifies during the heat exchange cooling process of the argon gas;

[0013] After gas pressure sintering, secondary electroplating of zinc-nickel alloy is performed on the zinc-nickel alloy coating after gas pressure sintering, and the zinc element in the secondary electroplating zinc-nickel alloy coating forms a zinc-zinc connection without an interface effect with the zinc element in the zinc-nickel alloy coating after gas pressure sintering.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects:

[0015] The present application improves the electroplating speed and makes the crystal more delicate by optimizing the electroplating process parameters, including the formula of the electroplating solution, thereby improving the flexibility of the zinc-nickel alloy coating, eliminating the undesirable powder shedding phenomenon during buckling and pressing, and improving the corrosion resistance of the zinc-nickel alloy coating. The salt spray test of the zinc-nickel alloy coating of the same thickness can reach 1000 hours without red rust or black spots, which is about 300 hours longer than the salt spray test of the traditional coating.

[0016] In the present application, the conventional electroplated zinc-nickel alloy coating is formed by the accumulation of micro-nano-level zinc particles and nickel particles that are invisible to the naked eye, that is, the electroplated zinc-nickel alloy coating is not completely solid, and there are micro-nano-level pores between adjacent particles, which are not tightly closed and airtight. Pores mean loopholes and breakthroughs, which will subsequently become breakthroughs that are easily corroded, just like ant holes in a thousand-mile dike, which will weaken the corrosion resistance of the zinc-nickel alloy coating;

[0017] Furthermore, the zinc particles and nickel particles are adsorbed on the surface of the metal joint by the electric field force. The zinc particles and nickel particles only fall on the surface of the metal joint. This adsorption leads to: first, there are gaps such as empty bags and hollow drums between the zinc-nickel alloy coating of the zinc particles and the surface of the metal joint; second, the connection between the zinc particles and the nickel particles and the surface of the metal joint is weak, and powder is easily shed. Obviously, these gaps such as empty bags and hollow drums and the weak connection force and easy shedding of powder will weaken the corrosion resistance of the zinc-nickel alloy coating;

[0018] To this end, the electroplating process includes a primary electroplating of zinc-nickel alloy and a secondary electroplating of zinc-nickel alloy;

[0019] Gas pressure sintering is also included between the primary electroplating of zinc-nickel alloy and the secondary electroplating of zinc-nickel alloy. After the gas pressure sintering is completed, the secondary electroplating of zinc-nickel alloy is performed on the zinc-nickel alloy coating after the gas pressure sintering.

[0020] Here, the thickness of the primary electroplated zinc-nickel alloy coating is 1 / 4-1 / 3 of the total thickness of the entire zinc-nickel alloy coating (approximately 2 microns to 4 microns), that is, it is only a very thin layer. The thinner layer is used to serve as a foundation, a base, and a transition layer for the subsequent thicker secondary electroplated zinc-nickel alloy coating. Secondly, the thinner thickness and the relatively short gas pressure sintering heat preservation time of 5-15 minutes make it possible for the subsequent zinc to melt and become zinc liquid without flowing. A thin layer of zinc liquid wets the surface of the metal joint, and the zinc liquid has no obvious flow, runoff, and dripping, just like a thin mist only wets the surface of a leaf.

[0021] During the gas pressure sintering process, the zinc element in the primary electroplated zinc-nickel alloy coating melts and becomes zinc liquid, and all zinc particles melt to become integrated zinc liquid. The nickel particles do not melt but are immersed in the zinc liquid, so that the pores between zinc particles, between zinc particles and nickel particles, and between nickel particles in the primary electroplated zinc-nickel alloy coating disappear.

[0022] The high pressure of argon gas presses the molten zinc liquid tightly against the surface of the metal joint so that there are no gaps such as empty bags and hollows between the primary electroplated zinc-nickel alloy coating and the surface of the metal joint;

[0023] The high pressure of argon compresses the molten zinc liquid to penetrate into the surface layer of the metal joint, causing the zinc liquid to react with the iron element in the metal joint to form a zinc-iron alloy transition layer, that is, forming a mutually interlocking transition layer structure of "you in me, I in you". Obviously, this mutually interlocking transition layer structure has the following functions:

[0024] (1) The metal joint is made of steel, while the coating is made of zinc-nickel alloy. The two are different materials, and there is an interface effect between them. This interface effect will obviously weaken the adhesion and corrosion resistance of the zinc-nickel alloy coating. However, the above-mentioned transition layer has a mutually interlocking structure of "you in me, I in you", resulting in no interface between the metal joint and the zinc-nickel alloy coating, and thus no interface effect, thus solving the above-mentioned problem of the traditional interface effect weakening the adhesion and corrosion resistance;

[0025] (2) The formation of the transition layer allows the primary electroplated zinc-nickel alloy coating to be deeply rooted in the surface layer of the metal joint. The connection force and connection strength of the interlocking structure of the transition layer are obviously much greater than the above-mentioned electric field force, so that the primary electroplated zinc-nickel alloy coating is more firmly fixed on the surface of the metal joint and is not easy to peel off and shed;

[0026] (3). The transition layer is only a thin layer to lay a solid foundation, and the secondary electroplated zinc-nickel alloy coating is the thicker zinc-nickel alloy coating of the main body. Because of the solid foundation of the transition layer, and both the primary electroplated zinc-nickel alloy coating and the secondary electroplated zinc-nickel alloy coating are zinc-nickel alloy materials, there is no interface effect between the two. Therefore, the connection force and connection strength between the secondary electroplated zinc-nickel alloy coating and the primary electroplated zinc-nickel alloy coating will be greater, and the secondary electroplated zinc-nickel alloy coating will be more firmly fixed on the primary electroplated zinc-nickel alloy coating, thereby making the entire zinc-nickel alloy coating more firmly fixed on the surface of the metal joint, and not easy to peel off, fall off, and powder. Just like building a high-rise building, laying the foundation is very important. If the foundation is well laid and firmly laid, it will be more convenient and efficient to build a building on the foundation later, and the entire high-rise building will be more stable;

[0027] In summary, the pores between the above-mentioned particles disappear, there are no empty pockets, hollows and other gaps, and the zinc-iron alloy transition layer is generated, which overcomes the above-mentioned structural defects in the traditional zinc-nickel alloy coating, thereby improving the adhesion and corrosion resistance of the zinc-nickel alloy coating. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present application provides a method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe, comprising the following steps in sequence: pretreatment, pickling, neutralization, electroplating treatment to prepare a zinc-nickel alloy coating, passivation, sealing, and drying.

[0030] In one embodiment of the present application, the plating solution in the electroplating process comprises the following components: 6-12 g / L ZnO, 80-140 g / L NaOH, 40-80 mL / L nickel complexing agent, 50-85 mL / L zinc complexing agent, 0.6-2 mL / L nickel supplementer, and 0.5-1 mL / L tank opening additive.

[0031] In one embodiment of the present application, the zinc-nickel alloy coating includes the following elements in percentage by mass: 12.5%-15.5% nickel element, and the balance zinc element;

[0032] The thickness of the zinc-nickel alloy coating is 8 micrometers to 12 micrometers.

[0033] In one embodiment of the present application, the electroplating process includes a primary electroplating of zinc-nickel alloy and a secondary electroplating of zinc-nickel alloy, and the thickness of the primary electroplating zinc-nickel alloy coating is 1 / 4-1 / 3 of the total thickness of the zinc-nickel alloy coating, and the thickness of the secondary electroplating zinc-nickel alloy coating is 2 / 3-3 / 4 of the total thickness of the zinc-nickel alloy coating;

[0034] A gas pressure sintering treatment is also included between the primary electroplating zinc-nickel alloy and the secondary electroplating zinc-nickel alloy, specifically: the metal joint with the primary electroplating zinc-nickel alloy coating is placed in a gas pressure sintering furnace, and then the gas pressure sintering furnace is evacuated to 0.1-10Pa, and then argon is filled into the gas pressure sintering furnace, and the pressure of the argon in the gas pressure sintering furnace is controlled to be 5-20MPa, and then the gas pressure sintering furnace starts to heat up, and the temperature is raised to 425℃-600℃ to perform heat preservation sintering treatment on the metal joint with the primary electroplating zinc-nickel alloy coating, and the gas pressure sintering heat preservation time is 5-15min, and then the high-temperature argon in the gas pressure sintering furnace is subjected to inter-wall heat exchange cooling treatment until the argon temperature in the furnace is reduced to 25℃-50℃, and then the argon in the furnace is discharged, and then the furnace is opened to take out the parts;

[0035] During the gas pressure sintering process, the zinc element in the primary electroplated zinc-nickel alloy coating melts and turns into zinc liquid, so that the pores between the particles in the primary electroplated zinc-nickel alloy coating disappear, the high pressure of the argon gas presses the molten zinc liquid tightly against the surface of the metal joint, so that there is no gap between the primary electroplated zinc-nickel alloy coating and the surface of the metal joint, the high pressure of the argon gas presses the molten zinc liquid to penetrate into the surface layer of the metal joint, so that the zinc liquid reacts with the iron element in the metal joint to form a zinc-iron alloy transition layer, and then the zinc liquid cools and solidifies during the heat exchange cooling process of the argon gas;

[0036] After gas pressure sintering, secondary electroplating of zinc-nickel alloy is performed on the zinc-nickel alloy coating after gas pressure sintering, and the zinc element in the secondary electroplating zinc-nickel alloy coating forms a zinc-zinc connection without an interface effect with the zinc element in the zinc-nickel alloy coating after gas pressure sintering.

[0037] In the present application, electroplating belongs to zincate zinc plating, which is to use ZnO and NaOH to prepare a solution, add appropriate zinc plating additives, and plate a layer of metal zinc nickel on the surface of metal or other materials under power-on state to increase the corrosion resistance and decorativeness of the material. Alkaline zincate zinc plating uses zinc oxide as the main salt and sodium hydroxide (caustic soda) as the complexing agent. It is characterized by being non-corrosive to electroplating equipment, fine and bright coating, low cost, wide source of raw materials, stable bath solution, and easy to control. Appropriate amount of additives must be added to make the coating achieve fine and bright crystal effect.

[0038] In this application, during the electroplating process, passivation refers to the formation of a non-dissolving passivation layer on the surface of the coating. The methods for forming the passivation layer include chemical passivation, electrochemical passivation, and heat treatment passivation (which is the same as the gas pressure sintering treatment in this application, i.e., this application is a composite plating treatment method of electroplating and heat treatment), etc. This passivation layer can prevent the metal surface from being further oxidized, thereby achieving an anti-corrosion effect. Passivation treatment can increase the corrosion resistance and wear resistance of the metal surface and improve the overall quality of metal parts; passivation can also be used to change the color of the metal surface or enhance the gloss of the metal surface; passivation treatment in electroplating can also be used to increase the conductivity of metal materials, which is very useful for applications in the electronic and electrical fields.

[0039] In this application, the sealant used in the sealing treatment is a reagent used for rust and corrosion prevention treatment of metal stamping iron parts, various standard parts, etc. after plating. The electroplating sealant has extremely strong anti-rust and salt spray resistance, is not easy to burn, is environmentally friendly and non-toxic, and can form a dense protective film on the surface of the metal (the effect of the workpiece after electroplating is better). It has extremely strong anti-rust, anti-corrosion, and anti-discoloration effects. It is easy to use and easy to operate, and the required equipment is simple. It is suitable for metal stamping iron parts, various standard parts, etc. after plating (such as nickel plating, black nickel, tin, zinc, chromium, etc. ) is used for anti-rust and anti-corrosion treatment, which is widely used in electroplating, continuous electroplating, chemical nickel plating, etc. The anti-rust ability and salt spray resistance of the workpiece treated with the sealant are greatly enhanced, the surface gloss is good, and it will not stick together, and will not affect conductivity and welding; the sealant has high anti-corrosion performance and strong adhesion, does not contain formaldehyde, benzene, heavy metals and other harmful substances, and becomes a transparent and bright film layer after drying, which can be used as the final anti-corrosion layer. The sealing layer has excellent brightness, flatness, anti-discoloration, corrosion resistance and high adhesion.

[0040] In this application, gas pressure sintering is a sintering process carried out under high pressure atmosphere. Its principle is to fill the gaps between particles under high temperature and high pressure to promote the bonding between particles, thereby forming a dense and continuous material in a short time. Compared with the traditional sintering method, gas pressure sintering has the advantages of short sintering time, uniform temperature, and good product quality. Gas pressure sintering refers to applying a certain gas pressure, usually nitrogen or argon, in the pressure range of 5-20MPa during high temperature sintering, thereby increasing the sintering speed, further promoting the densification of the material, and obtaining a high-density sintered product.

[0041] In this application, a salt spray machine (salt spray test chamber) is a device used to simulate a salt spray environment and test the corrosion resistance of materials. It is used for salt spray corrosion tests of parts, electronic components, protective layers of metal materials, and industrial products. It is divided into neutral tests, acid tests, alkaline tests, etc. The test methods that can be used include: neutral salt spray test (NSS test), salt spray test (SS test), acetic acid salt spray test (ASS test), copper accelerated vinegar instinct test, high temperature and humidity test, etc.

[0042] The methods and devices not described in detail in the present invention are all prior art and will not be described in detail.

[0043] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0044] Example 1

[0045] The method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe in Example 1 comprises the following steps in sequence: pretreatment, pickling, neutralization, electroplating to prepare a zinc-nickel alloy coating, passivation, sealing, and drying;

[0046] The electroplating solution in the electroplating process contains the following components: 8 g / L ZnO, 120 g / L NaOH, 50 mL / L nickel complexing agent, 65 mL / L zinc complexing agent, 1.0 mL / L nickel supplement, 0.6 mL / L tank opening additive;

[0047] The zinc-nickel alloy coating comprises the following elements in percentage by mass: 13.2% nickel and the remainder zinc;

[0048] The thickness of the zinc-nickel alloy coating is 10.3 microns.

[0049] Example 2

[0050] The method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe according to Example 2 comprises the following steps in sequence: pretreatment, pickling, neutralization, electroplating to prepare a zinc-nickel alloy coating, passivation, sealing, and drying;

[0051] The electroplating solution in the electroplating process contains the following components: 10 g / L ZnO, 110 g / L NaOH, 65 mL / L nickel complexing agent, 55 mL / L zinc complexing agent, 1.2 mL / L nickel supplement, 0.7 mL / L tank opening additive;

[0052] The zinc-nickel alloy coating comprises the following elements in percentage by mass: 12.7% nickel and the remainder zinc;

[0053] The thickness of the zinc-nickel alloy coating is 10.9 microns.

[0054] Example 3

[0055] The method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe in Example 3 comprises the following steps in sequence: pretreatment, pickling, neutralization, electroplating to prepare a zinc-nickel alloy coating, passivation, sealing, and drying;

[0056] The electroplating solution in the electroplating treatment contains the following components: 12 g / L ZnO, 100 g / L NaOH, 70 mL / L nickel complexing agent, 60 mL / L zinc complexing agent, 2 mL / L nickel supplement, 0.5 mL / L tank opening additive;

[0057] The zinc-nickel alloy coating comprises the following elements in percentage by mass: 14.1% nickel and the remainder zinc;

[0058] The thickness of the zinc-nickel alloy coating is 11.2 microns;

[0059] The electroplating treatment includes a primary electroplating of zinc-nickel alloy and a secondary electroplating of zinc-nickel alloy, wherein the thickness of the primary electroplating zinc-nickel alloy coating is 1 / 4-1 / 3 of the total thickness of the zinc-nickel alloy coating, and the thickness of the secondary electroplating zinc-nickel alloy coating is 2 / 3-3 / 4 of the total thickness of the zinc-nickel alloy coating;

[0060] A gas pressure sintering treatment is also included between the primary electroplating zinc-nickel alloy and the secondary electroplating zinc-nickel alloy, specifically: the metal joint with the primary electroplating zinc-nickel alloy coating is placed in a gas pressure sintering furnace, and then the gas pressure sintering furnace is evacuated to 0.1-10Pa, and then argon is filled into the gas pressure sintering furnace, and the pressure of the argon in the gas pressure sintering furnace is controlled to be 8-10MPa, and then the gas pressure sintering furnace starts to heat up, and the temperature is raised to 430℃-440℃ to perform heat preservation sintering treatment on the metal joint with the primary electroplating zinc-nickel alloy coating, and the gas pressure sintering heat preservation time is 15min, and then the high-temperature argon in the gas pressure sintering furnace is subjected to inter-wall heat exchange cooling treatment until the argon temperature in the furnace is reduced to 25℃-35℃, and then the argon in the furnace is discharged, and then the furnace is opened to take out the parts;

[0061] During the gas pressure sintering process, the zinc element in the primary electroplated zinc-nickel alloy coating melts and turns into zinc liquid, so that the pores between the particles in the primary electroplated zinc-nickel alloy coating disappear, the high pressure of the argon gas presses the molten zinc liquid tightly against the surface of the metal joint, so that there is no gap between the primary electroplated zinc-nickel alloy coating and the surface of the metal joint, the high pressure of the argon gas presses the molten zinc liquid to penetrate into the surface layer of the metal joint, so that the zinc liquid reacts with the iron element in the metal joint to form a zinc-iron alloy transition layer, and then the zinc liquid cools and solidifies during the heat exchange cooling process of the argon gas;

[0062] After gas pressure sintering, secondary electroplating of zinc-nickel alloy is performed on the zinc-nickel alloy coating after gas pressure sintering, and the zinc element in the secondary electroplating zinc-nickel alloy coating forms a zinc-zinc connection without an interface effect with the zinc element in the zinc-nickel alloy coating after gas pressure sintering.

[0063] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe, characterized in that: The method comprises the following steps which are carried out in sequence: pretreatment, pickling, neutralization, electroplating, passivation, sealing and drying.

2. The method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe according to claim 1, characterized in that: The plating solution in the electroplating process contains the following components: 6-12 g / L ZnO, 80-140 g / L NaOH, 40-80 mL / L nickel complexing agent, 50-85 mL / L zinc complexing agent, 0.6-2 mL / L nickel supplement, and 0.5-1 mL / L tank opening additive.

3. The method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe according to claim 1, characterized in that: The zinc-nickel alloy coating comprises the following elements in percentage by mass: 12.5% ​​to 15.5% nickel and the remainder zinc; The thickness of the zinc-nickel alloy coating is 8 micrometers to 12 micrometers.

4. The method for preparing a zinc-nickel alloy coating of a metal joint of an automobile oil pipe according to claim 1, characterized in that: The electroplating treatment includes a primary electroplating of zinc-nickel alloy and a secondary electroplating of zinc-nickel alloy, wherein the thickness of the primary electroplating zinc-nickel alloy coating is 1 / 4-1 / 3 of the total thickness of the zinc-nickel alloy coating, and the thickness of the secondary electroplating zinc-nickel alloy coating is 2 / 3-3 / 4 of the total thickness of the zinc-nickel alloy coating; A gas pressure sintering treatment is also included between the primary electroplating zinc-nickel alloy and the secondary electroplating zinc-nickel alloy, specifically: the metal joint with the primary electroplating zinc-nickel alloy coating is placed in a gas pressure sintering furnace, and then the gas pressure sintering furnace is evacuated to 0.1-10Pa, and then argon is filled into the gas pressure sintering furnace, and the pressure of the argon in the gas pressure sintering furnace is controlled to be 5-20MPa, and then the gas pressure sintering furnace starts to heat up, and the temperature is raised to 425℃-600℃ to perform heat preservation sintering treatment on the metal joint with the primary electroplating zinc-nickel alloy coating, and the gas pressure sintering heat preservation time is 5-15min, and then the high-temperature argon in the gas pressure sintering furnace is subjected to inter-wall heat exchange cooling treatment until the argon temperature in the furnace is reduced to 25℃-50℃, and then the argon in the furnace is discharged, and then the furnace is opened to take out the parts; During the gas pressure sintering process, the zinc element in the primary electroplated zinc-nickel alloy coating melts and turns into zinc liquid, so that the pores between the particles in the primary electroplated zinc-nickel alloy coating disappear, the high pressure of the argon gas presses the molten zinc liquid tightly against the surface of the metal joint, so that there is no gap between the primary electroplated zinc-nickel alloy coating and the surface of the metal joint, the high pressure of the argon gas presses the molten zinc liquid to penetrate into the surface layer of the metal joint, so that the zinc liquid reacts with the iron element in the metal joint to form a zinc-iron alloy transition layer, and then the zinc liquid cools and solidifies during the heat exchange cooling process of the argon gas; After gas pressure sintering, secondary electroplating of zinc-nickel alloy is performed on the zinc-nickel alloy coating after gas pressure sintering, and the zinc element in the secondary electroplating zinc-nickel alloy coating forms a zinc-zinc connection without an interface effect with the zinc element in the zinc-nickel alloy coating after gas pressure sintering.