CN112941593A

CN112941593A - Vacuum impregnation of anodized coated (AOC) surfaces on valve metal substrates

Info

Publication number: CN112941593A
Application number: CN202011437799.2A
Authority: CN
Inventors: K·A·森塔; S·J·韩
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2019-12-11
Filing date: 2020-12-11
Publication date: 2021-06-11
Also published as: DE102020131128A1; US20210180203A1

Abstract

A corrosion resistant workpiece is provided. The corrosion resistant workpiece includes: a substrate comprising a valve metal or an alloy comprising a valve metal; an oxide layer formed on the substrate, the oxide layer comprising a plurality of pores, wherein each of the plurality of pores has a pore volume; and a polymer composition disposed in at least a portion of the plurality of pores, wherein for each pore in which the polymer composition is disposed, greater than or equal to about 70% of the pore volume is filled by the polymer composition. A method of making the corrosion resistant article is also provided.

Description

Vacuum impregnation of anodized coated (AOC) surfaces on valve metal substrates

Background

This section provides background information related to the present disclosure that is not necessarily prior art.

Valve metals and their alloys are increasingly used in aerospace and automotive applications due to their light weight and high strength. However, valve metals can corrode under a variety of conditions, including in the presence of humid air and water. This corrosion is exacerbated by the presence of various salts and other known corrosive agents. Even though some surface protection is provided by forming an oxide layer on the valve metal using a micro-arc oxidation (MAO) coating, the oxide layer still has a high porosity, which allows moist air and/or water to penetrate into the oxide layer and contact the valve metal surface. Accordingly, a method of providing corrosion resistance to a workpiece comprising a valve metal is desired.

Disclosure of Invention

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

In various aspects, the present techniques provide a corrosion resistant workpiece comprising: a substrate comprising a valve metal or an alloy comprising a valve metal; an oxide layer formed on the substrate, the oxide layer comprising a plurality of pores, wherein each of the plurality of pores has a pore volume; and a polymer composition disposed in at least a portion of the plurality of pores, wherein for each pore in which the polymer composition is disposed, greater than or equal to about 70% of the pore volume is filled by the polymer composition.

In one aspect, the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof.

In one aspect, the oxide layer is formed on the substrate by micro-arc oxidation.

In one aspect, the polymer composition includes a polyacrylate.

In one aspect, the polymer composition comprises polyacrylic acid (PAA), polymethacrylic acid (PMA), Polymethylmethacrylate (PMMA), Polyethylacrylate (PEA), Polyethylmethacrylate (PEMA), or a combination thereof.

In one aspect, the polymer composition is disposed in greater than or equal to about 95% of the plurality of pores.

In one aspect, for each pore in which the polymer composition is disposed, greater than or equal to about 90% of the pore volume is filled by the polymer composition.

In one aspect, the oxide layer is substantially free of voids when no additional layer is disposed on the oxide layer.

In one aspect, the corrosion resistant article is a part of an automotive vehicle selected from a wheel (a wheel), a pillar (a pilar), a bracket (a breaker), a bumper (a damper), a roof rail (a roof rail), a rocker rail (a rocker rail), a rocker arm (a rocker), a control arm (a control arm), a beam (a beam), a channel (a tunnel), a step (a step), a subframe member (a subframe member), a disc (a pan), a plate (a panel), or a reinforcement plate (a reinforcement panel).

In various other aspects, the present techniques provide a method of making a corrosion resistant workpiece. The method comprises the following steps: transferring a workpiece into a chamber at least partially filled with a monomer resin, the workpiece comprising: a substrate comprising a valve metal or an alloy comprising a valve metal, and an oxide layer formed on the substrate, the oxide layer comprising a plurality of pores, wherein each pore of the plurality of pores has a pore volume; applying a vacuum to the chamber and removing air from the plurality of holes; releasing the vacuum and forcing the monomer resin to be disposed in at least a portion of the plurality of holes; and converting the monomer resin disposed in at least a portion of the plurality of pores to a polymer composition and forming a corrosion resistant workpiece, wherein for each pore in which the polymer composition is disposed, greater than or equal to about 70% of the pore volume is filled by the polymer composition.

In one aspect, each of the plurality of pores has a diameter greater than or equal to about 0.5 μm to less than or equal to about 20 μm at an exposed surface of the oxide layer.

In one aspect, applying the vacuum comprises applying a vacuum pressure of greater than or equal to about 0.1 torr to less than or equal to about 0.5 torr for a period of greater than or equal to about 1 minute to less than or equal to about 6 hours.

In one aspect, converting the monomer resin to a polymer composition includes curing the monomer resin at a temperature of greater than or equal to about ambient or room temperature to less than or equal to about 100 ℃ for a period of time of greater than or equal to about 1 minute to less than or equal to about 1 hour.

In one aspect, the method further comprises, after converting, applying a primer layer to the workpiece.

In other aspects, the present techniques provide a method of making a corrosion resistant workpiece, the method comprising: removing air contained in a plurality of pores defined by an oxide layer having a porosity of about 20% or more to about 90% or less, the oxide layer being formed on a substrate of a workpiece, wherein the substrate contains a valve metal or an alloy containing a valve metal, and each of the plurality of pores has a pore volume; actively forcing a monomer resin into at least a portion of the plurality of pores; curing the monomer resin in at least a portion of the plurality of pores to produce a corrosion resistant workpiece, wherein for each pore having the polymer composition disposed therein, greater than or equal to about 90% of the pore volume is filled by the polymer composition.

In one aspect, removing air contained in the plurality of holes is performed by applying a vacuum to a chamber containing the workpiece and the monomeric resin, and actively forcing the monomeric resin into at least a portion of the plurality of holes is performed by releasing the vacuum.

In one aspect, the monomer resin comprises a monomer selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, ethyl methacrylate, salts thereof, and combinations thereof.

In one aspect, the oxide layer of the corrosion resistant workpiece is substantially free of voids.

Specifically, the present invention includes the following items:

1. a corrosion resistant workpiece comprising:

a substrate comprising a valve metal or an alloy comprising a valve metal;

an oxide layer formed on the substrate, the oxide layer comprising a plurality of pores, wherein each of the plurality of pores has a pore volume; and

a polymer composition disposed within at least a portion of the plurality of pores, wherein for each pore in which the polymer composition is disposed, greater than or equal to about 70% of the pore volume is filled by the polymer composition.

2. The corrosion resistant workpiece of item 1, wherein said valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof.

3. The corrosion resistant workpiece of item 1, wherein the oxide layer is formed on the substrate by micro-arc oxidation.

4. The corrosion resistant article of item 1, wherein the polymer composition comprises a polyacrylate.

5. The corrosion resistant workpiece of item 1, wherein the polymer composition comprises polyacrylic acid (PAA), polymethacrylic acid (PMA), Polymethylmethacrylate (PMMA), Polyethylacrylate (PEA), Polyethylmethacrylate (PEMA), or a combination thereof.

6. The corrosion resistant workpiece of item 1, wherein the polymer composition is disposed in greater than or equal to about 95% of the plurality of pores.

7. The corrosion resistant workpiece of item 6, wherein, for each pore having the polymer composition disposed therein, greater than or equal to about 90% of the pore volume is filled by the polymer composition.

8. The corrosion resistant workpiece of item 1, wherein the oxide layer is substantially free of voids when no additional layer is disposed on the oxide layer.

9. The corrosion resistant workpiece of item 1, wherein said corrosion resistant workpiece is a part of an automotive vehicle selected from the group consisting of a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker beam, a rocker arm, a control arm, a cross beam, a tunnel, a step, a sub-frame member, a plate, a panel, and a reinforcement panel.

10. A method of making a corrosion resistant workpiece, the method comprising:

transferring a workpiece into a chamber at least partially filled with a monomer resin, the workpiece comprising: a substrate comprising a valve metal or an alloy comprising a valve metal, and an oxide layer formed on the substrate, the oxide layer comprising a plurality of pores, wherein each pore of the plurality of pores has a pore volume;

applying a vacuum to the chamber and removing air from the plurality of holes;

releasing the vacuum and forcing the monomer resin to be disposed in at least a portion of the plurality of holes; and

converting the monomeric resin disposed in at least a portion of the plurality of pores to a polymer composition and forming a corrosion resistant workpiece,

wherein for each pore in which the polymer composition is disposed, greater than or equal to about 70% of the pore volume is filled by the polymer composition.

11. The method of item 10, wherein each of the plurality of pores has a diameter of greater than or equal to about 0.5 μm to less than or equal to about 20 μm at an exposed surface of the oxide layer.

12. The method of item 10, wherein the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof.

13. The method of item 10, wherein the applying the vacuum comprises applying a vacuum pressure of greater than or equal to about 0.1 torr to less than or equal to about 0.5 torr for a period of greater than or equal to about 1 minute to less than or equal to about 6 hours.

14. The method of item 10, wherein converting the monomeric resin to the polymer composition comprises curing the monomeric resin at a temperature of greater than or equal to about ambient or room temperature to less than or equal to about 100 ℃ for a period of time of greater than or equal to about 1 minute to less than or equal to about 1 hour.

15. The method of item 10, further comprising: after the conversion, the reaction mixture is subjected to a reaction,

a primer layer is applied to the workpiece.

16. A method of making a corrosion resistant workpiece, the method comprising:

removing air contained in a plurality of pores defined by an oxide layer having a porosity of about 20% or more to about 90% or less, the oxide layer being formed on a substrate of a workpiece, wherein the substrate contains a valve metal or an alloy containing a valve metal, and each of the plurality of pores has a pore volume;

actively forcing a monomer resin into at least a portion of the plurality of pores;

curing the monomeric resin in at least a portion of the plurality of holes to produce a corrosion resistant workpiece,

wherein for each pore in which the polymer composition is disposed, greater than or equal to about 90% of the pore volume is filled by the polymer composition.

17. The method of item 16, wherein the removing the air contained in the plurality of holes is performed by applying a vacuum to a chamber containing the workpiece and the monomeric resin, and actively forcing the monomeric resin into at least a portion of the plurality of holes is performed by releasing the vacuum.

18. The method of item 16, wherein the monomer resin comprises a monomer selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, ethyl methacrylate, salts thereof, and combinations thereof.

19. The method of item 16, wherein the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof.

20. The method of item 16, wherein the oxide layer of the corrosion resistant workpiece is substantially free of voids.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

Fig. 1A is a micrograph showing a porous surface of an oxide layer formed on a first magnesium substrate by micro-arc oxidation. The scale bar is 10 μm.

Fig. 1B is a micrograph showing the porous surface of the oxide layer formed on the second magnesium substrate by micro-arc oxidation. The scale bar is 5 μm.

Fig. 2A is a photomicrograph showing a cross-section of a first workpiece having a magnesium substrate, an oxide layer formed on the magnesium substrate by micro-arc oxidation, and an epoxy powder primer layer coating the oxide layer. The scale bar is 10 μm.

Fig. 2B is a photomicrograph showing a cross-section of a second workpiece having a magnesium substrate, an oxide layer formed on the magnesium substrate by micro-arc oxidation, and a polyester primer layer coating the oxide layer. The scale bar is 10 μm.

Fig. 2C is a micrograph showing an enlarged portion of the micrograph of fig. 2B taken at box 2C. The scale bar is 5 μm.

FIG. 3A is a schematic illustration of a workpiece comprising a substrate comprising a valve metal or valve metal alloy and having a porous oxide layer formed thereon by micro-arc oxidation, wherein the workpiece is immersed in a monomeric resin, in accordance with aspects of the present technique.

FIG. 3B is a schematic illustration of the workpiece of FIG. 3A when a vacuum is applied and air is removed from the porous oxide layer and the monomer resin of the workpiece in accordance with aspects of the present technique.

Fig. 3C is a schematic illustration of the workpiece of fig. 3B when the vacuum is removed and the monomer resin is forced into the pores of the porous oxide layer of the workpiece in accordance with aspects of the present technique.

FIG. 4A is a schematic representation of a workpiece comprising a porous oxide layer formed by micro-arc oxidation on a substrate comprising a valve metal or valve metal alloy. In accordance with various aspects of the present technique, the workpiece is in a state in which air is removed from the pores of the porous oxide layer.

FIG. 4B is a schematic illustration of the workpiece shown in FIG. 4A, wherein all air has been removed from the holes, thereby leaving the holes vacant, in accordance with aspects of the present technique.

FIG. 4C is a schematic illustration of the workpiece shown in FIG. 4B as a monomer resin is forced into the holes of the workpiece in accordance with aspects of the present technique.

Fig. 4D is a schematic illustration of the workpiece shown in fig. 4C when the monomer resin is cured to produce a polymer composition in the pores of the porous oxide layer in accordance with aspects of the present technique.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Detailed Description

Some exemplary embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that these specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some exemplary embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having," are inclusive and therefore specify the presence of stated features, elements, components, steps, integers, operations, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Although the open-ended term "comprising" should be understood as a non-limiting term used to describe and claim various embodiments set forth herein, in certain aspects the term may alternatively be understood as a more limiting and constraining term, such as "consisting of or" consisting essentially of. Thus, for any given embodiment that lists compositions, materials, components, elements, features, integers, operations, and/or process steps, the disclosure also specifically includes embodiments that consist of, or consist essentially of, the recited compositions, materials, components, elements, features, integers, operations, and/or process steps. In the case of "consisting of", alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations, and/or process steps, and in the case of "consisting essentially of …", any additional compositions, materials, components, elements, features, integers, operations, and/or process steps that substantially affect the basic features and novel features are not included in the embodiments, but any compositions, materials, components, elements, features, integers, operations, and/or process steps that do not substantially affect the basic features and novel features may be included in the embodiments.

Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It should also be understood that additional or alternative steps may be used unless otherwise indicated.

When an element, component or layer is referred to as being "on," "engaged to," "connected to" or "coupled to" another element or layer, it can be directly on, engaged, connected or coupled to the other element, component or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to" or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements (e.g., "between" and "directly between," "adjacent" and "directly adjacent," etc.) should be interpreted in a similar manner. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms unless otherwise specified. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as "first," "second," and other numerical terms, when used herein, do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially or temporally relative terms, such as "before", "after", "inside", "outside", "below", "lower", "above", "upper", and the like, may be used herein for convenience in describing the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. In addition to the orientations depicted in the figures, the spatial or temporal relative terms may also be intended to encompass different orientations of the device or system in use or operation.

Throughout this disclosure, numerical values represent approximate measurements or boundaries of ranges, to encompass minor deviations from the given values and embodiments having approximately the recited values as well as embodiments having exactly the recited values. Other than the working examples provided at the end of the detailed description, in this specification including the appended claims, all numbers expressing parameters (e.g., quantities or conditions) are to be understood as being modified in all instances by the term "about," whether or not "about" actually appears before the number. "about" means that the numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). As used herein, the term "about" refers at least to variations that may result from ordinary methods of measuring and using such parameters, provided that the imprecision provided by "about" is not otherwise understood in the art with this ordinary meaning. For example, "about" can include a change of less than or equal to 5%, optionally a change of less than or equal to 4%, optionally a change of less than or equal to 3%, optionally a change of less than or equal to 2%, optionally a change of less than or equal to 1%, optionally a change of less than or equal to 0.5%, and in certain aspects, optionally a change of less than or equal to 0.1%.

In addition, the disclosure of a range includes disclosure of all values and further sub-ranges within the entire range, including the endpoints and sub-ranges given for that range.

Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings.

An oxide layer, for example by micro-arc oxidation (MAO), disposed on a workpiece formed from a substrate comprising a valve metal or an alloy comprising a valve metal, inhibits corrosion to some extent relative to a corresponding workpiece not having the oxide layer. However, the oxide layer is porous, which allows the external environment to communicate with the underlying substrate and cause corrosion. FIGS. 1A-1B show micrographs of the surface of an oxide layer formed by MAO on a magnesium workpiece, with the scale bar in FIG. 1 being 10 μm and the scale bar in FIG. 1B being 5 μm. From these micrographs, it can be seen that the oxide layer has a high porosity. Air and moisture can penetrate into these pores and cause corrosion at the interface between the magnesium substrate and the oxide layer. In an attempt to inhibit this corrosion, additional coatings have been applied over the oxide layer. For example, primers, polymers, fluoropolymers, epoxies, powder coatings, paints, varnishes and combinations thereof have been applied to the oxide layer. These coatings are applied by, for example, dipping, spraying, electrocoating, and brushing. However, these coatings are generally porous in nature, which still allows the underlying substrate to communicate with the external environment and be corroded. For example, fig. 2A is a photomicrograph showing a workpiece 10, the workpiece 10 including a magnesium substrate 12, an oxide layer 14 formed on the magnesium substrate 12 by micro-arc oxidation, and an epoxy powder primer layer 16 (scale bar 10 μm) coating the oxide layer 14, and fig. 2B is a photomicrograph showing a workpiece 20, the workpiece 20 including a magnesium substrate 22, an oxide layer 24 formed on the magnesium substrate 22, and a polyester primer layer 26 (scale bar 20 μm) coating the oxide layer 24. Fig. 2C is an enlarged portion of the workpiece 20 of fig. 2B extracted at block 2C. These micrographs show the porosity of the oxide layers 14, 24 and indicate that the primer layers 16, 26 do not penetrate into the oxide layers 14, 24. Thus, any pores in the

primer layer

16, 26 may communicate the

magnesium substrate

12, 22 with the environment outside of the

workpiece

10, 20, which may lead to corrosion.

Thus, the present technique provides a method of filling pores of an oxide layer to prevent, inhibit, or minimize corrosion formation by blocking communication between the underlying substrate and the external environment. Also provided are corrosion resistant workpieces prepared by the method.

More particularly, the present technology relates generally to enhanced surface coatings for workpieces containing valve metals. As used herein, the term "valve metal" is used to refer to a metal or metal alloy that is capable of growing a nanoporous oxide film by MAO techniques. The resulting oxide layer formed on the valve metal can provide a degree of corrosion protection as it constitutes a physical barrier between the metal and the corrosive environment. However, as described above, it may not provide sufficient corrosion resistance. Exemplary valve metals that may be used in the present technology include magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof. The valve metal may exhibit an electrically rectifying behavior in the electrolytic cell and, for a given applied current, will maintain a higher potential when the anode is charged than when the cathode is charged.

Referring to fig. 3A, the present technique provides a method for preparing a corrosion resistant workpiece from a workpiece 30, the workpiece 30 comprising a valve metal or valve metal alloy substrate 31 (see fig. 4A), i.e., a substrate comprising a valve metal or valve metal alloy. The workpiece 30 may consist of or consist essentially of a valve metal or valve metal alloy, i.e. the substrate 31 may also contain only unintentional but unavoidable impurities. The substrate 31 defines the shape of the workpiece 30. The workpiece 30 is not limited and may be, for example, any part or object made from a valve metal or from an alloy containing a valve metal, such as a vehicle part. Non-limiting examples of vehicles having components suitable for production by the present method include bicycles, automobiles, motorcycles, boats, tractors, buses, mobile homes, campers, gliders, airplanes, and tanks. In various aspects, the workpiece 30 is an automotive component selected from a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker, a control arm, a cross beam, a tunnel, a step, a sub-frame member, a plate, a panel, or a reinforcement panel. Thus, while the workpiece 30 is shown as a post, it should be understood that this is an exemplary aspect and the workpiece is in no way limited to posts.

The method includes cleaning and desmutting the workpiece 30 and forming an oxide layer 32 on the exposed surface of the substrate 31. This oxide layer 32 can be seen in fig. 4A-4D, which show cross-sectional views of the workpiece 30 when the method is performed. The oxide layer 32 may be formed using MAO techniques to produce when the substrate 31 includes magnesium, aluminum, and titanium, respectively, for example, a magnesium oxide or magnesium oxide ceramic layer, an aluminum oxide or aluminum oxide ceramic layer, or a titanium oxide or titanium oxide ceramic layer, the composition of which may vary based on the electrolyte and other materials present therein. Various conventional and commercial variations of the MAO process may be used, including those described in U.S. patent No. 3,293,158, U.S. patent No. 5,792,335, U.S. patent No. 6,365,028, U.S. patent No. 6,896,785, and U.S. patent publication No. 2012/0031765, each of which is incorporated herein by reference in its entirety. In one example, the MAO process may be performed using a silicate-based electrolyte, which may include sodium silicate, potassium hydroxide, and potassium fluoride. An oxide layer 32 is formed into and out of the surface of the substrate 31 to produce an oxide layer thickness T of greater than or equal to about 1 μm to less than or equal to about 60 μm_OLIncluding thicknesses of about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 55 μm, and about 60 μm (see FIG. 4A). As a non-limiting example, the oxide layer formed on magnesium by MAO has a thickness greater than or equal to about 8 μm to less than or equal to about 12 μm.

As can be seen in fig. 4A-4D (and the photomicrographs of fig. 1A-1B), the oxide layer 32 includes a plurality of pores 34, wherein each pore 34 of the plurality of pores has a pore volume and a diameter, i.e., the longest diameter, of greater than or equal to about 0.5 μm to less than or equal to about 20 μm or greater than or equal to about 0.5 μm to less than or equal to about 10 μm at the exposed surface of the oxide layer, including diameters of 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm. Thus, the oxide layer 32 has a porosity (i.e., a fraction of the total volume of pores based on the total volume of the oxide layer 32) of greater than or equal to about 40% to less than or equal to about 85%, including porosities of about 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and 85%.

After forming the oxide layer 32 on the substrate 31, the method includes cleaning and passivating the workpiece 30 by rinsing with pH neutral deionized water. Cleaning and passivating removes particles and electrolyte from the surface of the workpiece 30 and thus from the matrix 31.

Returning to fig. 3A, the method then includes transferring the workpiece 30 into a chamber 36 at least partially filled with a monomer resin 38. However, it should be understood that the workpiece 30 may be transferred to the monomer resin 38 preloaded into the cavity 36, or may be transferred into the cavity 36, and then the monomer resin 38 introduced into the cavity 36 until it completely covers the workpiece 30. In either manner, the workpiece 30 is completely immersed in the monomer resin 38. The interior of chamber 36 communicates with a source of negative pressure (not shown), such as vacuum, through port 40 and conduit 42.

The monomer resin 38 comprises a monomer capable of polymerizing to form a polymer and a carrier. Non-limiting exemplary monomers include acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, ethyl methacrylate, salts thereof, and combinations thereof. The carrier may be any carrier that provides the following characteristics and may include, as non-limiting examples, polyethylene glycol dimethacrylate, lauryl methacrylate, hydroxyalkyl methacrylate, surfactants, and combinations thereof. An exemplary carrier comprises 60 wt.% polyethylene glycol dimethacrylate, 30 wt.% lauryl methacrylate, 5 wt.% hydroxyalkyl methacrylate, and 5 wt.% surfactant. The monomer resin 38 has properties that allow the monomer resin to eventually fill the pores 34 of the oxide layer 32. These properties include a surface tension less than the surface tension of water (72.8 dynes/cm at 20 ℃), for example a surface tension of greater than or equal to about 28 dynes/cm to less than or equal to about 63 dynes/cm, and a viscosity of greater than or equal to about 5Cp to less than or equal to about 20 Cp. The monomers are capable of polymerizing and forming polymers such as polyacrylic acid (PAA), polymethacrylic acid (PMA), Polymethylmethacrylate (PMMA), Polyethylacrylate (PEA), Polyethylmethacrylate (PEMA), and combinations thereof.

When the workpiece 30 is immersed in the monomer resin 38, as shown in fig. 4A, the holes 34 are filled with air 44. Accordingly, the method includes removing the air 44 contained within the plurality of holes 34. As shown in fig. 3B, removal of the air 44 (shown in fig. 4A) contained in the plurality of holes 34 may be performed by applying a negative pressure (i.e., vacuum) to the interior of the chamber by means of a negative pressure source (i.e., conduit 42 and port 40). In various aspects, the negative pressure is greater than or equal to about 0.1 torr to less than or equal to about 0.5 torr, including pressures of about 0.1 torr, about 0.15 torr, about 0.2 torr, about 0.25 torr, about 0.3 torr, about 0.35 torr, about 0.4 torr, about 0.45 torr, and about 0.5 torr. When negative pressure is applied, air 44 is removed from the holes 34 and monomer resin 38, which can be observed as air pockets 46 containing air 44 shown in FIG. 4A. The formation of air pockets 46 may be violent to an observer and may be similar to the boiling of the monomer resin 38. As indicated by the upward arrows in fig. 3B and 4A, the air pocket 46 and corresponding air 44 rise from both the monomer resin 38 and the plurality of holes 34 and are exhausted from the chamber 36 via the port 40. The negative pressure and resulting air removal is carried out for a period of time greater than or equal to about 1 minute to less than or equal to about 6 hours, including times of about 1 minute, about 30 minutes, about 1 hour, about 1.5 hours, about 2 hours, about 2.5 hours, about 3 hours, about 3.5 hours, about 4 hours, about 4.5 hours, about 5 hours, about 5.5 hours, and about 6 hours, or until no more air pockets 46 are seen, indicating that all of the air 44 has been removed from the pores 34 and the monomer resin 38. Fig. 4B shows the oxide layer 32 in a state where the pores 34 are empty, i.e. without any gas or liquid.

After removing substantially all of the air 44 from the pores, where substantially all of the air refers to at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 99% of the air, the method includes actively forcing the monomer resin 38 into the plurality of pores 34. By "actively forcing" is meant that a force other than gravity must be applied to fill the hole 34 with the monomer resin 38. In some aspects, as shown in fig. 3C and 4C, the negative pressure is released, which causes air to rush into the chamber 36 and force the monomer resin 38 downward and against the workpiece 30, such that the monomer resin 38 enters and fills the holes 34. This air pressure is indicated by the downward arrow in the figure. The monomer resin 38 enters at least a portion of the pores, such as greater than or equal to about 80%, greater than or equal to about 85%, or greater than or equal to about 90% of the pores 34, or enters substantially all of the pores (greater than or equal to about 95% of the pores 34). Also, for each pore 34 in which monomer resin 38 is disposed, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 85%, greater than or equal to about 90%, or substantially all (greater than or equal to about 95%) of the pore volume is filled by monomer resin 38. Thus, in some aspects, substantially all of the pore volume of substantially all of the pores 34 is filled with the monomer resin 38.

After the monomer resin 38 has been actively forced into the bore 34, the workpiece 30 is removed from the cavity 36, or the monomer resin 38 remaining in the cavity 36 is removed, such as by draining. Residual monomer resin 38 is then removed from the surface of the workpiece 30, for example, by rinsing with a solvent (e.g., water) or by centrifugation.

Referring to fig. 4D, the method further includes converting the monomeric resin 38 disposed in at least a portion of the hole 34 into a polymer composition 48 and forming a corrosion resistant workpiece 50. In various aspects, the conversion is carried out as follows: curing the monomer resin 38 in at least a portion of the plurality of holes 34 at a temperature of greater than or equal to about ambient or room temperature to less than or equal to about 100 ℃, including a temperature of about 20 ℃, about 25 ℃, about 30 ℃, about 35 ℃, 40 ℃, 45 ℃, about 50 ℃, about 55 ℃, about 60 ℃, about 65 ℃, about 70 ℃, about 75 ℃, about 80 ℃, about 85 ℃, about 90 ℃, about 95 ℃, or about 100 ℃, for a time period of greater than or equal to about 1 minute to less than or equal to about 1 hour, including a time period of about 1 minute, about 5 minutes, about 10 minutes, about 15 minutes, about 20 minutes, about 25 minutes, about 30 minutes, about 35 minutes, about 40 minutes, about 45 minutes, about 50 minutes, about 55 minutes, or about 1 hour, to produce the corrosion resistant workpiece 50. The polymer composition 48 comprises the polymerization product of the monomers provided in the monomer resin 38, and may include, as non-limiting examples, polyacrylic acid (PAA), polymethacrylic acid (PMA), Polymethylmethacrylate (PMMA), Polyethylacrylate (PEA), Polyethylmethacrylate (PEMA), and combinations thereof. Curing may be performed in the chamber 36, on a countertop (e.g., at ambient or room temperature), or in a separate oven. After curing, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 85%, greater than or equal to about 90%, or substantially all (greater than or equal to about 95%) of the pore volume is filled by the polymer composition 48 for each pore 34 in which the monomer resin 38 is disposed. Thus, in some aspects, substantially all of the pore volume of substantially all of the pores 34 is filled by the polymer composition 48. In these aspects, the oxide layer 32 of the corrosion resistant workpiece 50 is substantially free of empty pores, i.e., less than or equal to about 20%, less than or equal to about 15%, less than or equal to about 10%, less than or equal to about 5%, or less than or equal to about 1% of previously empty pores 34 remain empty.

The method then includes rinsing the corrosion resistant workpiece 50 in the chamber 36 or at a different location. For example, the steps of immersing the workpiece 30 in the polymer resin, applying negative pressure, draining, rinsing, centrifuging, heating, and rinsing may be performed in a single apparatus that includes the chamber 36. However, it is to be understood that each step may also be performed in or in association with a separate device.

The method then optionally includes applying additional coatings or layers to the corrosion resistant workpiece 50, such as layers including primers, polymers, fluoropolymers, epoxies, powder coatings, paints, dye coatings, basecoats, varnishes, and combinations thereof.

The present technique also provides a corrosion resistant workpiece 50 prepared by the above method. The corrosion-resistant workpiece 50 must include a base 31 containing a valve metal or an alloy containing a valve metal and an oxide layer 32 formed on the base 31, the oxide layer 32 including a plurality of pores 34, wherein each of the plurality of pores has a pore volume. The polymer composition 48 is disposed within at least a portion of the plurality of pores 34, wherein for each pore 34 in which the polymer composition 48 is disposed, greater than or equal to about 70% of the pore volume is filled by the polymer composition 48.

The foregoing description of the embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but are interchangeable where applicable, and can be used in a selected embodiment even if not specifically shown or described. Which can likewise be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A corrosion resistant workpiece comprising:

a substrate comprising a valve metal or an alloy comprising a valve metal;

2. The corrosion resistant workpiece of claim 1, wherein the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof.

3. The corrosion resistant workpiece of claim 1, wherein the polymer composition comprises polyacrylic acid (PAA), polymethacrylic acid (PMA), Polymethylmethacrylate (PMMA), Polyethylacrylate (PEA), Polyethylmethacrylate (PEMA), or a combination thereof.

4. The corrosion resistant workpiece of claim 1, wherein the polymer composition is disposed within greater than or equal to about 95% of the plurality of pores, and greater than or equal to about 90% of the pore volume is filled by the polymer composition for each pore in which the polymer composition is disposed.

5. The corrosion resistant workpiece of claim 1, wherein the corrosion resistant workpiece is a part of an automotive vehicle selected from a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker arm, a control arm, a cross beam, a tunnel, a step, a sub-frame member, a plate, a panel, or a reinforcement panel.

6. A method of making a corrosion resistant workpiece, the method comprising:

applying a vacuum to the chamber and removing air from the plurality of holes;

7. The method of claim 6, wherein each of the plurality of pores has a diameter greater than or equal to about 0.5 μ ι η to less than or equal to about 20 μ ι η at an exposed surface of the oxide layer.

8. The method of claim 6, wherein the valve metal is selected from the group consisting of magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof.

9. The method of claim 6, wherein converting the monomer resin to the polymer composition comprises curing the monomer resin at a temperature of greater than or equal to about ambient or room temperature to less than or equal to about 100 ℃ for a period of time of greater than or equal to about 1 minute to less than or equal to about 1 hour.

10. The method of claim 6, further comprising: after the conversion, the reaction mixture is subjected to a reaction,

a primer layer is applied to the workpiece.