Hydrothermal black oxide conversion coating process for steel members
By forming a black oxide coating on steel components using a hydrothermal method, the problem of mud cracking was solved, costs and safety risks were reduced, and a uniform iron oxide film and iron sulfide flake coating were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-19
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies suffer from mud cracking issues when forming black oxide coatings, and conventional methods require strict health and safety controls and are costly.
A hydrothermal method is used to form a black oxide coating on steel components. This is achieved by stirring or circulating an oxidizing salt solution at a specific temperature to react with iron, avoiding ultrasonic treatment. Sodium metabisulfite, surfactants, and citric acid are used as the main components to form a uniform iron oxide film and a thin layer of iron sulfide flakes.
It achieves a uniform coating without mud cracking, reduces health and safety risks, reduces costs, and simplifies the process.
Smart Images
Figure CN121781130A_ABST
Abstract
Description
Technical Field
[0001] The technical field generally relates to methods for coating steel components with black oxide coatings and the products prepared therefrom. Background Technology
[0002] Various products, including vehicles, may have components that rotate or slide along bearings. Summary of the Invention
[0003] Multiple variations may include a method for forming a black oxide coating on an automotive component of an electric drive unit for a vehicle, the method comprising: providing an automotive component including a body having an outer surface, the automotive component comprising iron; placing the iron-containing automotive component in a black oxide conversion coating solution comprising at least one oxide salt; heating the black oxide conversion coating solution to a temperature ranging from about 20 degrees Celsius (°C) to 80°C; and stirring or circulating the black oxide conversion coating solution for about 20 seconds to about 80 seconds without subjecting the black oxide conversion coating solution to ultrasonic waves, such that at least one oxide salt reacts with the iron to form a black oxide coating on the automotive component.
[0004] Multiple variations may include a method that further includes cleaning the automotive parts, including iron, to remove residual oil from their outer surfaces before placing them in a black oxide conversion coating solution.
[0005] Multiple variations may include a method in which cleaning automotive parts includes: placing the automotive parts in a cleaning solution; and subjecting the automotive parts and the cleaning solution to ultrasonic waves.
[0006] Multiple variations may include a method that further includes rinsing a cleaning solution from an outer surface.
[0007] Multiple variations may include a method that further includes: rinsing the black oxide coating on the outer surface with an aqueous solution to remove the aqueous solution therefrom; and drying the outer surface to remove the aqueous solution from the black oxide coating.
[0008] Multiple variations may include a method in which at least one oxidizing salt comprises sodium metabisulfite present in about 5 wt% to about 20 wt% of the black oxide conversion coating solution.
[0009] Multiple variations may include a method in which the black oxide conversion coating solution further comprises about 3 wt% to about 15 wt% of a surfactant.
[0010] Multiple variations may include a method in which the black oxide conversion coating solution further comprises about 0.25 wt% to about 3 wt% citric acid.
[0011] Multiple variations may include a method wherein the temperature range is from about 25°C to about 65°C.
[0012] Multiple variations may include a method wherein the temperature range is from about 30°C to about 60°C.
[0013] Several variations may include a method for forming a black oxide coating on an automotive component of an electric drive unit for a vehicle, the method comprising: providing a bearing including a body having an outer surface, the bearing comprising iron; placing the bearing comprising iron in a black oxide conversion coating solution, the black oxide conversion coating solution comprising about 5 wt% to about 15 wt% sodium metabisulfite, about 3 wt% to about 15 wt% surfactant and about 0.25 wt% to about 3 wt% citric acid; heating the black oxide conversion coating solution to a temperature ranging from about 30°C to 60°C; and stirring or circulating the black oxide conversion coating solution for about 30 seconds to about 60 seconds without subjecting the black oxide conversion coating solution to ultrasonic waves to form a black oxide coating on the bearing.
[0014] Multiple variations may include a system for forming a black oxide coating on an automotive component of an electric drive unit for a vehicle, the system comprising: a tank having a black oxide conversion coating solution; a stirrer having at least a portion of the black oxide conversion coating solution; a heater having at least a portion of the black oxide conversion coating solution; a robotic arm and a bearing retainer attached thereto; a computing device including an electronic processor; and a non-transitory storage medium having instructions executable by the electronic processor to perform functions including: providing a bearing comprising a body having an outer surface, the bearing comprising iron; placing the bearing comprising iron in a black oxide conversion coating solution comprising at least one oxide salt, the oxide salt being present in the black oxide conversion coating solution at about 5 wt% to about 20 wt% of the black oxide conversion coating solution; heating the black oxide conversion coating solution to a temperature ranging from about 20°C to 80°C; and stirring or circulating the black oxide conversion coating solution for less than 80 seconds without subjecting the black oxide conversion coating solution to ultrasonic waves, such that at least one oxide salt reacts with the iron to form a black oxide coating on the automotive component.
[0015] Multiple variations may include a system in which the black oxide coating has a thickness between 2 micrometers and 4 micrometers.
[0016] Multiple variations may include a system in which the black oxide coating is essentially free of mud cracking.
[0017] Multiple variations may include a system that further includes: rinsing the black oxide coating on the outer surface with an aqueous solution to remove the aqueous solution therefrom; and drying the outer surface to remove the aqueous solution from the black oxide coating.
[0018] Multiple variations may include a system in which at least one oxidizing salt comprises sodium metabisulfite present in about 5 wt% to about 15 wt% of the black oxide conversion coating solution.
[0019] Multiple variations may include a system in which the black oxide conversion coating solution further comprises about 3 wt% to about 15 wt% of a surfactant.
[0020] Multiple variations may include a system in which the black oxide conversion coating solution further comprises about 0.25 wt% to about 3 wt% citric acid.
[0021] Multiple variations may include a system in which the temperature range is from about 25°C to about 65°C.
[0022] Multiple variations may include a system in which the temperature range is from about 30°C to about 60°C. Attached Figure Description
[0023] The illustrative variations will be described below with reference to the following figures, wherein the same numerals denote the same elements, and wherein:
[0024] Figure 1 This is a flowchart illustrating multiple steps in a hydrothermal method for forming black oxides on a component including iron, according to various variations;
[0025] Figure 2 This is an illustration of several variations of a bearing having a black oxide coating formed thereon by a hydrothermal method;
[0026] Figure 3 The illustration shows a pair of SED-SEM images, where the image on the left is a black oxide coating produced by a hydrothermal method according to multiple variants, and the image on the right is a black oxide coating produced by an ultrasonic method.
[0027] Figure 4 A system for forming a black oxide coating on automotive components for electric drive units of vehicles, according to several variations, is shown; and
[0028] Figure 5 The diagram shows a vehicle with an electric drive unit according to several variants, the electric drive unit including a bearing assembly having a bearing having a black iron coating thereon, the black iron coating having no or substantially no mud cracking. Detailed Implementation
[0029] The following detailed description is merely exemplary in nature and is not intended to limit application and use. Furthermore, it is not intended to be bound by any express or implied theory presented in the foregoing introduction, the brief description of the figures, the brief overview, or the detailed description below.
[0030] Several disclosed variations may include systems and methods for coating components with black (iron) oxide. The component may be a ball bearing assembly of a rotating shaft in an electric drive unit for an automobile. The component includes a body and an outer surface, wherein the outer surface may be coated with a black oxide coating comprising an iron oxide film and iron sulfide flakes disposed on the iron oxide film. The outer surface of the component may be coated with the black oxide using a hydrothermal method. The hydrothermal method can reduce cycle time to between approximately 30 and 60 seconds. The hydrothermal method eliminates the need for pickling or pre-etching required by conventional alkaline salt processes. Furthermore, the hydrothermal method does not include conventional alkaline salt black oxide conversion coating processes using hydroxide and nitrate solutions, which require stringent health and safety controls. Additionally, the hydrothermal method eliminates the need for the large and expensive dedicated hydrostatic paths required by conventional ultrasonic black oxide coating methods.
[0031] Figure 1 This is a flowchart illustrating multiple actions in a method according to several variations, wherein the method may include action 22, which includes placing a component comprising iron in a black oxide conversion coating solution comprising at least one ionized salt. Action 24 may include heating the black oxide conversion coating solution to at least 30 degrees Celsius (°C). Action 26 may include stirring the black oxide conversion solution such that at least one ionized salt reacts with iron to form a black oxide on the component.
[0032] Figure 2 Through, for example but not limited to Figure 1 The method shown is illustrated with a bearing 28 having a black oxide coating 30 formed thereon. The black oxide coating formed on the surface of the bearing uniformly covers the surface of the bearing 28 and is free of mud cracks or at least substantially free of mud cracks.
[0033] Figure 3The illustration shows a pair of secondary electron detector-scanning electron microscope (SED-SEM) images, where image 32 on the left shows a black oxide coating produced by a hydrothermal method according to several variations, and image 34 on the right shows a black oxide coating produced using an ultrasonic method. Both coatings were applied to or formed on a ball bearing rolling element. The black oxide coating produced by the hydrothermal method contains significantly fewer "mud cracks" 36 than the black oxide coating produced by the ultrasonic method. Mud cracks 36, or "mud fissures," are formed due to internal stress in the black oxide coating produced by conventional alkaline salt or ultrasonic methods.
[0034] Several variations may include hydrothermal methods of coating automotive components (such as electric drive unit bearing assemblies) with iron oxide for use with electric drive units. Figure 1 Prior to action 22, the component can be cleaned to remove residual oil from its outer surface. In several variations, the component can be placed in a first tank containing a cleaning solution. An ultrasonic device can be positioned in the first tank and can generate ultrasonic waves that travel through the cleaning solution and impact the outer surface of the component. Thereafter, the component can be removed from the first tank and rinsed in the cleaning solution by spraying it with a water-based solution or by immersing it in the water-based solution.
[0035] After cleaning the components, the components, including those containing iron, can be placed in a black oxide conversion coating solution comprising at least one oxidizing salt. The oxidizing salt may include, but is not limited to, sodium metabisulfite (Na₂SO₃). In several variations, the black oxide conversion coating solution may include sodium metabisulfite (Na₂SO₃) in an amount ranging from about 3 wt% to about 20 wt% or any range, and this range may include at least one endpoint or any single wt% of sodium metabisulfite (Na₂SO₃) of 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 17 wt%, 18 wt%, or 19 wt%. The black oxide coating conversion solution may include a surfactant in an amount ranging from about 3 wt% to about 15 wt% or any range thereof, and this range may include at least one endpoint or any single weight percentage of 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, and 14 wt% of the surfactant. Without departing from the spirit or scope of this disclosure, the surfactant may be a liquid detergent comprising chlorosulfonated hydrocarbons, sodium dodecylbenzenesulfonate, or any other suitable solution. In several variations, the surfactant may include a commercially available surfactant under the trade name TEEPOL 610s. The black oxide coating conversion solution may include citric acid in an amount ranging from about 0.25 wt% to about 3 wt% or any range thereof, and this range may include at least one endpoint or a single weight percentage of 0.5 wt%, 0.8 wt%, 1 wt%, 1.3 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.3 wt%, 2.5 wt%, and 2.8 wt% of the citric acid. The remainder of the black oxide coating conversion solution can be water.
[0036] like Figure 1 As shown in action 24, the black oxide conversion coating solution can be heated to a temperature ranging from about 25 degrees Celsius (°C) to about 80°C, including any sub-range therebetween, and the range may include at least one endpoint temperature or any single temperature: 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C.
[0037] The black oxide conversion solution can be stirred or circulated in a tank for a period of time ranging from about 10 seconds to about 80 seconds or any subrange therebetween, and can include at least one time endpoint or a single time: 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 60 seconds, 70 seconds, or 75 seconds. The black oxide conversion coating method can produce a 1-4 μm iron oxide coating on the surface of a component. The black oxide conversion solution can be stirred or circulated, for example, using an electric stirrer, pump, or bubbler, but without subjecting the solution to ultrasound.
[0038] exist Figure 1 Following action 26, the hydrothermal method may further include drying the outer surface of the component including the coating formed thereon to remove any water-based / alcohol-based solution. In several variations, drying may be performed using air or nitrogen at a temperature ranging from about 40°C to about 50°C, employing a blower, drying cabinet, or drying tunnel.
[0039] A hydrothermal method can produce iron sulfide (FeS) flakes on the surface of a black oxide coating on a component. By stirring or circulating an appropriate amount of the black oxide conversion coating solution, the black oxide coating can be applied to the entire outer surface of the bearing. The black oxide coating produced by the hydrothermal method provides corrosion protection during the storage of the coated component.
[0040] Citric acid can be disposed to chemically activate the surface of the component and allow the reaction of oxygen / hydrogen substances with iron (Fe) to form ferric hydroxide Fe(OH)2. Sodium metabisulfite can be disposed to react with ferric hydroxide to generate ferric oxysulfide (FeSO3) on the component containing iron. Ferric oxysulfide can react with oxygen / hydrogen substances to produce an iron oxide (FeO, Fe2O3, Fe3O4) film and iron sulfide (FeS) flakes on the component containing iron. That is, a first portion of ferric oxysulfide reacts with oxygen to produce an iron oxide film on the outer surface of the component containing iron, and a second portion of ferric oxysulfide reacts with hydrogen to produce iron sulfide flakes disposed within the iron oxide film. In several variations, the black oxide coating 40 may include 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, and 95 wt% iron oxide between 50 wt% and 100 wt%. Furthermore, the black oxide coating 40 may include an amount of iron sulfide ranging from 0 wt% to about 50 wt% and any subrange therebetween, and this range may include at least one endpoint weight or a single weight of 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or 45 wt% of iron sulfide. Additionally, the black oxide coating may have a thickness ranging from about 0.5 micrometers to about 4 micrometers or any subrange therebetween, and may have at least one endpoint or a single thickness of 1 micrometer, 1.5 micrometers, 2 micrometers, 2.5 micrometers, 3 micrometers, or 3.5 micrometers.
[0041] Figure 4 A system for forming a black oxide coating on automotive components for an electric drive unit of a vehicle, according to several variations, is illustrated. System 300 may include a tank 330 and a stirrer 302, the stirrer including a motor 304 and a shaft connected at one end to the motor 304 and at the other end to a propeller 308. At least a portion of the stirrer 302 is immersed in a black oxide conversion coating solution 310 contained in the tank 330. System 300 may also include a heater 312 having at least a portion 314 immersed in the black oxide conversion coating solution 310. System 300 may include a robotic arm 326 operatively connected to a second motor 328 and a bearing retainer 324 for holding at least one bearing 28. The stirrer 302, robotic arm 326, and heater 312 may be connected to a computing device 316, which may include an electronic processor 318 and a non-transitory memory 320 having instructions 322 thereon to perform any of the functions described herein.
[0042] Figure 5This is a schematic diagram of a vehicle 400, which may include at least one front wheel 402 operably connected to at least one front axle 404. The vehicle 400 may include at least one rear wheel 406 operably connected to at least one rear axle 426. A steering interface 408 may be operably connected to a steering shaft 410. The steering shaft 410 may be operably connected to a steering rack 412, which may be operably connected to at least one front wheel 402. The vehicle 400 may include an electric drive unit 414 for propelling the vehicle 400. A front drive axle 416 may be operably connected to at least one front axle 404 and the electric drive unit 414. The front drive axle 416 may be supported by a first bearing assembly 420 including at least one bearing 28. A rear drive axle 422 may be operably connected to at least one rear axle 426 and the electric drive unit 414. The rear drive axle 422 may be supported by a second bearing assembly 424 including at least one bearing 28. A power source 428 (which may be a battery) may be operably connected to the electric drive unit 414 to supply power thereto. At least one bearing 28 may have a black iron coating thereon, which is free from or substantially free from mud cracking. At least one bearing 28 may be coated thereon with a black iron coating that is free from or substantially free from mud cracking by a method as described herein.
[0043] While at least one variation has been presented in the foregoing detailed description, it should be understood that numerous variations exist. It should also be understood that the variations or multiple variations are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing one or more illustrative variations. It should be understood that various changes can be made to the function and arrangement of the elements without departing from the scope of this disclosure as set forth in the appended claims and their legal equivalents.
Claims
1. A method for forming a black oxide coating on an automotive component of an electric drive unit for a vehicle, the method comprising: Provides an automotive component comprising a body having an outer surface, the automotive component comprising iron; The automotive component, which includes iron, is placed in a black oxide conversion coating solution comprising at least one oxidizing salt; The black oxide conversion coating solution is heated to a temperature ranging from about 20°C to 80°C; and The black oxide conversion coating solution is stirred or circulated for about 20 seconds to about 80 seconds without subjecting the black oxide conversion coating solution to ultrasound, so that the at least one oxide salt reacts with the iron to form a black oxide coating on the automotive part.
2. The method of claim 1, further comprising cleaning the automotive component, including iron, to remove residual oil from the outer surface before placing the automotive component in the black oxide conversion coating solution.
3. The method according to claim 2, wherein, Cleaning the automotive parts includes: The automotive components were placed in a cleaning solution; and The automotive components and the cleaning solution are subjected to ultrasonic waves.
4. The method of claim 3, further comprising rinsing the cleaning solution from the outer surface.
5. The method of claim 1, further comprising: Rinse the black oxide coating on the outer surface with an aqueous solution to remove the aqueous solution therefrom; as well as The outer surface is dried to remove the aqueous solution from the black oxide coating.
6. The method according to claim 1, wherein, The at least one oxidizing salt includes sodium metabisulfite present in about 5 wt% to about 20 wt% of the black oxide conversion coating solution.
7. The method according to claim 6, wherein, The black oxide conversion coating solution further comprises about 3 wt% to about 15 wt% of a surfactant.
8. The method according to claim 6, wherein, The black oxide conversion coating solution further comprises about 0.25 wt% to about 3 wt% citric acid.
9. The method according to claim 1, wherein, The temperature range is from about 30°C to about 60°C.
10. A system for forming a black oxide coating on an automotive component of an electric drive unit for a vehicle, the system comprising: A tank containing a black oxide conversion coating solution, a stirrer having at least a portion in the black oxide conversion coating solution, a heater having at least a portion in the black oxide conversion coating solution, a robotic arm and a bearing retainer attached thereto, a computing device including an electronic processor, and a non-transitory storage medium having instructions executable by the electronic processor to perform functions, said functions including: A bearing is provided comprising a body having an outer surface, the bearing comprising iron; The bearing comprising iron is placed in the black oxide conversion coating solution comprising at least one oxide salt, the oxide salt being present in the black oxide conversion coating solution at about 5 wt% to about 20 wt%. The black oxide conversion coating solution is heated to a temperature ranging from about 20°C to 80°C; and The black oxide conversion coating solution is stirred or circulated for less than 80 seconds without being subjected to ultrasound, so that the at least one oxide salt reacts with the iron to form a black oxide coating on the automotive part.