US20210180203A1

US20210180203A1 - Vacuum impregnation of anodic oxidation coating (aoc) treated surfaces on valve metal substrates

Info

Publication number: US20210180203A1
Application number: US16/711,407
Authority: US
Inventors: Kestutis A. Sonta; Su Jung Han
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2019-12-11
Filing date: 2019-12-11
Publication date: 2021-06-17
Also published as: CN112941593A; DE102020131128A1

Abstract

A corrosion-resistant workpiece is provided. The corrosion-resistant workpiece includes a matrix including a valve metal or an alloy including a valve metal; an oxide layer formed on the matrix, the oxide layer including a plurality of pores, wherein each pore of the plurality has a pore volume; and a polymeric composition disposed within at least a portion of the plurality of pores, wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition. A method of fabricating the corrosion-resistant workpiece is also provided.

Description

INTRODUCTION

This section provides background information related to the present disclosure which is not necessarily prior art.
Valve metals and their alloys are increasingly used in aerospace and automotive applications because of their light weight and high strength. However, valve metals corrode under a variety of conditions, including in the presence of humid air and water. Such corrosion is exacerbated in the presence of various salts and other known corrosive agents. Even though some surface protection is afforded by forming oxide layers on valve metals by microarc oxidation (MAO) coating, the oxide layers have a high porosity, which enables humid air and/or water to infiltrate the oxide layer and contact the valve metal surface. Accordingly, methods of providing corrosion-resistance to workpieces comprising a valve metal are desired.

SUMMARY

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 current technology provides a corrosion-resistant workpiece that includes a matrix comprising a valve metal or an alloy including a valve metal; an oxide layer formed on the matrix, the oxide layer including a plurality of pores, wherein each pore of the plurality has a pore volume; and a polymeric composition disposed within at least a portion of the plurality of pores, wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric 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 matrix by micro-arc oxidation.
In one aspect, the polymeric composition includes a polyacrylate.
In one aspect, the polymeric composition includes poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), or combinations thereof.
In one aspect, the polymeric composition is disposed within greater than or equal to about 95% of the plurality of pores.
In one aspect, greater than or equal to about 90% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.
In one aspect, the oxide layer is substantially free of vacant pores when no additional layer is disposed on the oxide layer.
In one aspect, the corrosion-resistant workpiece is a component of an automobile selected from the group consisting of a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker rail, a rocker, a control arm, a beam, a tunnel, a step, a subframe member, a pan, a panel, or a reinforcement panel.
In various other aspects, the current technology provides a method of fabricating a corrosion-resistant workpiece. The method includes transferring a workpiece into a chamber at least partially filled with a monomer resin, the workpiece including a matrix comprising a valve metal or an alloy including a valve metal and an oxide layer formed on the matrix, the oxide layer including a plurality of pores, wherein each pore of the plurality has a pore volume; applying a vacuum to the chamber and removing air from the plurality of pores; releasing the vacuum and forcing the monomer resin to be disposed in at least a portion of the plurality of pores; and converting the monomer resin disposed in the at least a portion of the plurality of pores into a polymeric composition and forming the corrosion-resistant workpiece, wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.
In one aspect, each pore of the plurality has a diameter at an exposed surface of the oxide layer of greater than or equal to about 0.5 μm to less than or equal to about 20 μm.
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 applying the vacuum includes 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 time period of greater than or equal to about 1 minute to less than or equal to about 6 hours.
In one aspect, the converting the monomer resin into a polymeric composition comprises curing the monomer resin at a temperature of greater than or equal to about ambient temperature or room temperature to less than or equal to about 100° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 1 hour.
In one aspect, the method further includes, after the converting, applying a primer layer to the workpiece.
In yet other aspects, the current technology provides a method of fabricating a corrosion-resistant workpiece, the method including removing air contained within a plurality of pores defined by an oxide layer having a porosity of greater than or equal to about 20% to less than or equal to about 90%, the oxide layer formed on a matrix of a workpiece, wherein the matrix includes a valve metal or an alloy including a valve metal and each pore of the plurality has a pore volume; actively forcing a monomer resin into at least a portion of the plurality of pores; and curing the monomer resin in the at least a portion of the plurality of pores to generate the corrosion-resistant workpiece, wherein greater than or equal to about 90% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.
In one aspect, the removing air contained within the plurality of pores is performed by applying a vacuum to a chamber containing the workpiece and the monomer resin and the actively forcing the monomer resin into the at least a portion of the plurality of pores is performed by releasing the vacuum.
In one aspect, the monomer resin comprises monomers selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylic acid, ethyl acrylic acid, ethyl methacrylic acid, salts thereof, and combinations thereof.
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 of the corrosion-resistant workpiece is substantially free of vacant pores.
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 matrix by micro-arc oxidation. The scale bar is 10 μm.

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

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

FIG. 2B is a micrograph showing a cross-section of a second workpiece having a magnesium matrix, an oxide layer formed on the magnesium matrix 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 a magnified 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 matrix comprising a valve metal or an alloy of a valve metal, the matrix having a porous oxide layer formed thereon by micro-arc oxidation, wherein the workpiece is submerged in a monomer resin in accordance with various aspects of the current technology.

FIG. 3B is a schematic illustration of the workpiece of FIG. 3A while a vacuum is applied and air is removed from the porous matrix of the workpiece and the monomer resin in accordance with various aspects of the current technology.

FIG. 3C is a schematic illustration of the workpiece of FIG. 3B while the vacuum is removed and the monomer resin is forced into pores of the porous matrix of the workpiece in accordance with various aspects of the current technology.

FIG. 4A is a schematic illustration of a workpiece comprising a porous oxide layer formed on a matrix comprising a valve metal or an alloy of a valve metal by micro-arc oxidation. The workpiece is in a state in which air is being removed from pores of the porous oxide layer in accordance with various aspects of the current technology.

FIG. 4B is a schematic illustration of the workpiece shown in FIG. 4A in which all of the air has been removed from the pores, thus leaving the pores vacant, in accordance with various aspects of the current technology.

FIG. 4C is a schematic illustration of the workpiece shown in FIG. 4B as a monomer resin is forced into the pores of the workpiece in accordance with various aspects of the current technology.

FIG. 4D is a schematic illustration of the workpiece shown in FIG. 4C as a monomer resin is cured to generate a polymeric composition in the pores of the porous matrix in accordance with various aspects of the current technology.

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

DETAILED DESCRIPTION

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are 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 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 example 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” may be 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, compositions, 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,” is to be understood as a non-restrictive term used to describe and claim various embodiments set forth herein, in certain aspects, the term may alternatively be understood to instead be a more limiting and restrictive term, such as “consisting of” or “consisting essentially of” Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and/or process steps, the present disclosure also specifically includes embodiments consisting of, or consisting essentially of, such recited compositions, materials, components, elements, features, integers, operations, and/or process steps. In the case of “consisting of” the alternative embodiment excludes any additional compositions, materials, components, elements, features, integers, operations, and/or process steps, while in the case of “consisting essentially of,” any additional compositions, materials, components, elements, features, integers, operations, and/or process steps that materially affect the basic and novel characteristics are excluded from such an embodiment, but any compositions, materials, components, elements, features, integers, operations, and/or process steps that do not materially affect the basic and novel characteristics can be included in the embodiment.
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 is also to be understood that additional or alternative steps may be employed, unless otherwise indicated.
When a component, element, or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other component, element, 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 should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). 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 indicated. 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,” “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially or temporally relative terms may be intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures.
Throughout this disclosure, the numerical values represent approximate measures or limits to ranges to encompass minor deviations from the given values and embodiments having about the value mentioned as well as those having exactly the value mentioned. Other than in the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. For example, “about” may comprise a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in certain aspects, optionally less than or equal to 0.1%.
In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range, including endpoints and sub-ranges given for the ranges.
Example embodiments will now be described more fully with reference to the accompanying drawings.
An oxide layer disposed on a workpiece formed from a matrix comprising a valve metal or an alloy comprising a valve metal, e.g., by micro-arc oxidation (MAO) inhibits corrosion to some extent relative to a corresponding workpiece that does not have the oxide layer. However, the oxide layer is porous, which allows an external environment to communicate with the underlying matrix and cause corrosion. FIGS. 1A-1B show micrographs of surfaces of oxide layers formed on magnesium workpieces by MAO, wherein the scale bar in FIG. 1A is 10 μm and the scale bar in FIG. 1B is 5 μm. As can be seen in these micrographs, the oxide layers have a high porosity. Air and humidity may penetrate these pores and cause corrosion at an interface between a magnesium matrix and the oxide layer. Additional coatings have been applied to oxide layers in attempts to inhibit this corrosion. For example, primers, polymers, fluoropolymers, epoxies, powder coatings, paints, clear coats, and combinations thereof have been applied to oxide layers. These coatings are applied by, for example, dipping, spraying, electrocoating, and brushing. However, these coatings are often porous themselves, which still allows the underlying matrix to communicate with the external environment and become corroded. For example, FIG. 2A is a micrograph showing a workpiece 10 comprising a magnesium matrix 12, an oxide layer 14 formed on the magnesium matrix 12 by micro-arc oxidation, and an epoxy powder primer layer 16 coating the oxide layer 14 (the scale bar is 10 μm) and FIG. 2B is a micrograph showing a workpiece 20 comprising a magnesium matrix 22, an oxide layer 24 formed on the magnesium matrix 22, and a polyester primer layer 26 coating the oxide layer 24 (the scale bar is 20 μm). FIG. 2C is a magnified portion of the workpiece 20 of FIG. 2B taken from box 2C. These micrographs illustrate the porosity of the oxide layers 14, 24 and show that the primer layers 16, 26 do not penetrate into the oxide layers 14, 24. Therefore, any pores in the primer layers 16, 26 may allow the magnesium matrices 12, 22 to communicate with an environment external of the workpieces 10, 20, which may cause corrosion.
Accordingly, the current technology provides a method of filling the pores of oxide layers to prevent, inhibit, or minimize corrosion formation by blocking communication between the underlying matrix and the external environment. Corrosion-resistant workpieces fabricated by the method are also provided.
More particularly, the current technology generally relates to enhanced surface coatings for workpieces comprising valve metals. As used herein, the term “valve metal” is used to refer to a metal or metal alloy that can grow nanoporous oxide films by MAO techniques. The resultant oxide layer formed on a valve metal may provide some degree of corrosion protection, as it constitutes a physical barrier between the metal and a corrosive environment. However, as discussed above, it may not provide sufficient corrosion resistance. Example valve metals that can be utilized with the present technology include magnesium, aluminum, titanium, zirconium, hafnium, chromium, cobalt, molybdenum, vanadium, tantalum, mixtures thereof, and alloys thereof. Valve metals may exhibit electrical rectifying behavior in an electrolytic cell and, under a given applied current, will sustain a higher potential when anodically charged than when cathodically charged.
With reference to FIG. 3A, the current technology provides a method for fabricating a corrosion-resistant workpiece from a workpiece 30 comprising a valve metal or valve metal alloy matrix 31 (see FIG. 4A), i.e., a matrix comprising a valve metal or an alloy of a valve metal. The workpiece 30 can consist of the valve metal or valve metal alloy, or consist essentially of the valve metal or valve metal alloy, i.e., the matrix 31 may only also include unintended, but unavoidable impurities. The matrix 31 defines the shape of the workpiece 30. The workpiece 30 is not limited and can be any part or object fabricated from a valve metal or from an alloy comprising a valve metal, such as a vehicle part, for example. Non-limiting examples of vehicles that have parts suitable to be produced by the current method include bicycles, automobiles, motorcycles, boats, tractors, buses, mobile homes, campers, gliders, airplanes, and tanks. In various aspects, the workpiece 30 is an automobile part selected from the group consisting of a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker rail, a rocker, a control arm, a beam, a tunnel, a step, a subframe member, a pan, a panel, or a reinforcement panel. Therefore, although the workpiece 30 is shown as a pillar, it is understood that this is an exemplary aspect and that the workpiece is not in any way limited to a pillar.
The method comprises cleaning and desmutting the workpiece 30 and forming an oxide layer 32 on an exposed surface the matrix 31. The oxide layer 32 can be seen in FIGS. 4A-4D, which show an illustrated cross-sectional view of the workpiece 30 as the method is performed. The oxide layer 32 may be formed using MAO techniques to yield, e.g., a layer of magnesia or a magnesium oxide ceramic, a layer of alumina or an alumina ceramic, or a layer of titanium oxide or a titanium oxide ceramic, when the matrix 31 comprises magnesium, aluminum, and titanium, respectively, the composition of which may vary based on the electrolyte and other materials present therein. Various conventional and commercial variants of the MAO processes, including those described in U.S. Pat. Nos. 3,293,158, 5,792,335, 6,365,028, 6,896,785, and U.S. Pub. No. 2012/0031765, may be employed, 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 that may include sodium silicate, potassium hydroxide, and potassium fluoride. The oxide layer 32 forms into the surface of the matrix 31 and away from the surface to yield an oxide layer thickness T_OLof greater than or equal to about 1 μm to less than or equal to about 60 μm, including 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 that forms on magnesium by MAO has a thickness of greater than or equal to about 8 μm to less than or equal to about 12 μm.
As can be seen in FIGS. 4A-4D (as well as in the micrographs of FIGS. 1A-1B), the oxide layer 32 comprises a plurality of pores 34, wherein each pore 34 of the plurality has a pore volume and a diameter, i.e., a longest diameter, at an exposed surface of the oxide layer 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, 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. Accordingly, the oxide layer 32 has a porosity (i.e., a fraction of the total volume of pores over 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 the oxide layer 32 is formed on the matrix 31, the method comprises cleaning and passivating the workpiece 30 by rinsing with pH neutral deionized water. The cleaning and passivating removes particulates and electrolytes from the surface of the workpiece 30 and, thus, from the matrix 31.
Referring back to FIG. 3A, the method then comprises transferring the workpiece 30 into a chamber 36 at least partially filled with a monomer resin 38. However, it is understood that the workpiece 30 can either be transferred into the monomer resin 38, which is preloaded into the chamber 36, or can be transferred into the chamber 36 and then the monomer resin 38 introduced into the chamber 36 until it completely covers the workpiece 30. In either manner, the workpiece 30 is completely submerged in the monomer resin 38. The interior of the chamber 36 communicates with a source of negative pressure, such as a vacuum, (not shown), by way of a port 40 and a conduit 42.
The monomer resin 38 comprises monomers that are capable of polymerizing to form a polymer and a carrier. Non-limiting exemplary monomers include acrylic acid, methacrylic acid, methyl methacrylic acid, ethyl acrylic acid, ethyl methacrylic acid, salts thereof, and combinations thereof. The carrier can be any carrier that provides the below described characteristics, and can include polyglycol dimethacrylate, lauryl methacrylate, hydroxyalkyl methacrylate, surfactants, and combinations thereof as non-limiting examples. An exemplary carrier includes 60 wt. % polyglycol dimethacylate, 30 wt. % lauryl methacrylate, 5 wt. % hydroxyalkyl methacrylate, and 5 wt. % surfactant. The monomer resin 38 has characteristics that allow the monomer resin to eventually fill the pores 34 of the oxide layer 32. These characteristics include surface tension that is less than the surface tension of water (72.8 dynes/cm at 20° C.), such as 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 5 Cp to less than or equal to about 20 Cp. The monomers are capable of polymerizing and forming polymers such as poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), and combinations thereof.
When the workpiece 30 is submerged in the monomer resin 38, the pores 34 are filled with air 44 as shown in FIG. 4A. Therefore, the method comprises removing the air 44 contained within the plurality of pores 34. As shown in FIG. 3B, the removal of the air 44 contained within the plurality of pores 34 (shown in FIG. 4A) can be performed by applying a negative pressure, i.e., a vacuum, to the interior of the chamber by way of the source of negative pressure, i.e., the conduit 42 and the 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. While the negative pressure is applied, the air 44 is removed from the pores 34 and from the monomer resin 38, which can be seen as air pockets 46 comprising the air 44 shown in FIG. 4A. To an observer, the air pocket 46 formation may be violent and may resemble boiling of the monomer resin 38. As shown by the upward arrows in FIGS. 3B and 4A, the air pockets 46 and corresponding air 44 are lifted out of both the monomer resin 38 and the plurality of pores 34 and out of the chamber 36 by way of the port 40. The negative pressure and resulting air removal is performed for a time period 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 the air pockets 46 can no longer be seen, which is an indication 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 vacant, i.e., void of any gas or liquid.
After substantially all of the air 44 has been removed 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 comprises actively forcing the monomer resin 38 into the plurality of pores 34. By “actively forcing” it is meant that a force other than gravity must be applied in order to fill the pores 34 within the monomer resin 38. In some aspects, and as shown in FIGS. 3C and 4C, the negative pressure is released, which causes a rush of air to enter the chamber 36 and force the monomer resin 38 downward and against the workpiece 30 so that the monomer resin 38 enters and fills the pores 34. This air pressure is shown by the downward facing arrows in the figures. 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). Moreover, 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 for each pore 34 having the monomer resin 38 disposed therein is filled with the monomer resin 38. Therefore, in some aspects, substantially all of the pore volume of substantially all of the pores 34 are filled with the monomer resin 38.
After the monomer resin 38 has been actively forced into the pores 34, either the workpiece 30 is removed from the chamber 36 or the monomer resin 38 remaining in the chamber 36 is removed, such as by draining. Residual monomer resin 38 is then removed from surfaces of the workpiece 30, such as by rinsing with a solvent (e.g., water) or by centrifuging.
With reference to FIG. 4D, the method also comprises converting the monomer resin 38 disposed within the at least a portion of the pores 34 into a polymeric composition 48 and forming a corrosion-resistant workpiece 50. In various aspects the converting is performed by curing the monomer resin 38 in the at least a portion of the plurality of pores 34 at a temperature of greater than or equal to about ambient temperature or room temperature to less than or equal to about 100° C., including temperatures of about 20° C., about 25° C., about 30° C., about 35° C., about 40° C., about 45° C., about 50° C., about 55° C., about 60° C., about 65° C., about 70° C., about 75° C., about 80° C., about 85° C., about 90° C., about 95° C., or about 100° C., for a time period of greater than or equal to about 1 minute to less than or equal to about 1 hour, including times 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 generate the corrosion-resistant workpiece 50. The polymeric composition 48 comprises a polymerization product of the monomer provided in the monomer resin 38, and may comprise poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), and combinations thereof, as non-limiting examples. The curing can be performed in the chamber 36, on a countertop (e.g., when at ambient or room temperature), or in a separate oven. After the 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 for each pore 34 that had the monomer resin 38 disposed therein is filled with the polymeric composition 48. Therefore, in some aspects, substantially all of the pore volume of substantially all of the pores 34 are filled with the polymeric composition 48. In such aspects, the oxide layer 32 of the corrosion-resistant workpiece 50 is substantially free of vacant 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 the previously vacant pores 34 remain vacant.
The method then includes rinsing the corrosion-resistant workpiece 30, either in the chamber 36 or at a different location. For example, the steps of submerging the workpiece 30 into a polymer resin, applying the negative pressure, draining, rinsing, centrifuging, heating, and rinsing can be performed in a single apparatus that includes the chamber 36. However, it is understood that each step can also be performed in, or in association with, separate apparatuses.
The method optionally then comprises applying additional coatings or layers to the corrosion-resistant workpiece 50, such as a layer comprising a primer, polymer, fluoropolymer, epoxy, powder coating, paint, dye coat, base coat, clear coat, and combinations thereof.
The current technology also provides the corrosion-resistant workpiece 50 made by the above method. Necessarily, the corrosion-resistant workpiece 50 comprises the matrix 31 comprising the valve metal or the alloy comprising the valve metal and the oxide layer 32 formed on the matrix 31, the oxide layer 32 comprising the plurality of pores 34, wherein each pore of the plurality has a pore volume. The polymeric composition 48 is disposed within the at least a portion of the plurality of pores 34, wherein greater than or equal to about 70% of the pore volume for each pore 34 having the polymeric composition 48 disposed therein is filled with the polymeric composition 48.
The foregoing description of the embodiments has been provided 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, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also 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

What is claimed is:

1. A corrosion-resistant workpiece comprising:

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

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

a polymeric composition disposed within at least a portion of the plurality of pores, wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.

2. The corrosion-resistant workpiece according to 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 according to claim 1, wherein the oxide layer is formed on the matrix by micro-arc oxidation.

4. The corrosion-resistant workpiece according to claim 1, wherein the polymeric composition comprises a polyacrylate.

5. The corrosion-resistant workpiece according to claim 1, wherein the polymeric composition comprises poly(acrylic acid) (PAA), poly(methacrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethylacrylate) (PEA), poly(ethyl methacrylate) (PEMA), or combinations thereof.

6. The corrosion-resistant workpiece according to claim 1, wherein the polymeric composition is disposed within greater than or equal to about 95% of the plurality of pores.

7. The corrosion-resistant workpiece according to claim 6, wherein greater than or equal to about 90% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.

8. The corrosion-resistant workpiece according to claim 1, wherein the oxide layer is substantially free of vacant pores when no additional layer is disposed on the oxide layer.

9. The corrosion-resistant workpiece according to claim 1, wherein the corrosion-resistant workpiece is a component of an automobile selected from the group consisting of a wheel, a pillar, a bracket, a bumper, a roof rail, a rocker rail, a rocker, a control arm, a beam, a tunnel, a step, a subframe member, a pan, a panel, or a reinforcement panel.

10. A method of fabricating 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 matrix comprising a valve metal or an alloy comprising a valve metal and an oxide layer formed on the matrix, the oxide layer comprising a plurality of pores, wherein each pore of the plurality has a pore volume;

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

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

converting the monomer resin disposed in the at least a portion of the plurality of pores into a polymeric composition and forming the corrosion-resistant workpiece,

wherein greater than or equal to about 70% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.

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

12. The method according to claim 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 according to claim 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 time period of greater than or equal to about 1 minute to less than or equal to about 6 hours.

14. The method according to claim 10, wherein the converting the monomer resin into a polymeric composition comprises curing the monomer resin at a temperature of greater than or equal to about ambient temperature or room temperature to less than or equal to about 100° C. for a time period of greater than or equal to about 1 minute to less than or equal to about 1 hour.

15. The method according to claim 10, further comprising, after the converting:

applying a primer layer to the workpiece.

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

removing air contained within a plurality of pores defined by an oxide layer having a porosity of greater than or equal to about 20% to less than or equal to about 90%, the oxide layer formed on a matrix of a workpiece, wherein the matrix comprises a valve metal or an alloy comprising a valve metal and each pore of the plurality has a pore volume;

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

curing the monomer resin in the at least a portion of the plurality of pores to generate the corrosion-resistant workpiece,

wherein greater than or equal to about 90% of the pore volume for each pore having the polymeric composition disposed therein is filled with the polymeric composition.

17. The method according to claim 16, wherein the removing air contained within the plurality of pores is performed by applying a vacuum to a chamber containing the workpiece and the monomer resin and the actively forcing the monomer resin into the at least a portion of the plurality of pores is performed by releasing the vacuum.

18. The method according to claim 16, wherein the monomer resin comprises monomers selected from the group consisting of acrylic acid, methacrylic acid, methyl methacrylic acid, ethyl acrylic acid, ethyl methacrylic acid, salts thereof, and combinations thereof.

19. The method according to claim 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 according to claim 16, wherein the oxide layer of the corrosion-resistant workpiece is substantially free of vacant pores.