U.S. patent application number 15/641513 was filed with the patent office on 2019-01-10 for hydrophobic coating for corrosion protection and method of fabrication.
The applicant listed for this patent is Saudi Arabian Oil Company. Invention is credited to Gasan Selman Alabedi, Enrico Bovero, Aziz Fihri.
Application Number | 20190010335 15/641513 |
Document ID | / |
Family ID | 63013152 |
Filed Date | 2019-01-10 |
United States Patent
Application |
20190010335 |
Kind Code |
A1 |
Bovero; Enrico ; et
al. |
January 10, 2019 |
HYDROPHOBIC COATING FOR CORROSION PROTECTION AND METHOD OF
FABRICATION
Abstract
A method of fabricating a hydrophobic coating on a surface of a
solid substrate which includes a layer-integrable material includes
the steps of depositing a deformable layer of the layer-integrable
material onto the surface of the solid substrate, forcibly
embedding a plurality of particles within the deformable layer, and
solidifying the deformable layer including the plurality of
particles so as to be integral with the surface of the solid
substrate. At least a portion of the plurality of particles is
embedded at a threshold depth within the deformable layer prior to
solidification.
Inventors: |
Bovero; Enrico; (Reggio
Emilia, IT) ; Alabedi; Gasan Selman; (Gatley, GB)
; Fihri; Aziz; (Dhahran, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
|
SA |
|
|
Family ID: |
63013152 |
Appl. No.: |
15/641513 |
Filed: |
July 5, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 2201/011 20130101;
B05D 2451/00 20130101; B05D 5/08 20130101; C08K 3/36 20130101; C09D
5/084 20130101; C08K 2201/005 20130101; C09D 5/08 20130101; C09D
5/1681 20130101; C09D 163/00 20130101; B05D 7/54 20130101; C09D
7/61 20180101; C09D 7/67 20180101; B05D 2451/00 20130101; B05D
2401/32 20130101; B05D 2401/40 20130101 |
International
Class: |
C09D 5/08 20060101
C09D005/08; C09D 7/12 20060101 C09D007/12; C09D 163/00 20060101
C09D163/00 |
Claims
1. A method of fabricating a hydrophobic coating on a surface of a
solid substrate which includes a layer-integrable material, the
method comprising: depositing a deformable layer of the
layer-integrable material onto the surface of the solid substrate;
forcibly embedding a plurality of particles within the deformable
layer; and solidifying the deformable layer including the plurality
of particles so as to be integral with the surface of the solid
substrate, wherein at least a portion of the plurality of particles
is embedded at a threshold depth within the deformable layer prior
to solidification.
2. The method of claim 1, wherein the step of forcibly embedding a
plurality of particles within the deformable layer includes
bombarding the deformable layer with a stream of particles at
selected momenta.
3. The method of claim 1, wherein the plurality of particles have a
size in a range of about 1 nm to about 50 .mu.m.
4. The method of claim 3, wherein the plurality of particles have a
size in the range of about 5 nm to about 50 nm.
5. The method of claim 1, wherein the plurality of particles has a
size distribution ranging between 1 and 50 percent from an average
size value.
6. The method of claim 1, wherein the plurality of particles has a
multimodal size distribution.
7. The method of claim 1, wherein the deformable layer is deposited
in one of a fluid, semi-viscous or viscous form.
8. The method of claim 1, wherein the first material comprises an
epoxy resin.
9. The method of claim 8, wherein the plurality of particles are
composed of silica.
10. The method of claim 1, wherein upon solidification of the
deformable layer, the plurality of particles have a hierarchical
morphology such that a portion of the plurality of particles are
exposed on a surface of the solidified deformable layer, and a
portion of the plurality of particles are fully embedded with the
solidified deformable layer.
11. A hydrophobic coating, comprising: a matrix of layer-integrable
material; and a plurality of particles embedded at varying depths
within the matrix of layer-integrable material; wherein the
plurality of particles have a size in a range of about 1 nm to
about 50 .mu.m.
12. The hydrophobic coating of claim 11, wherein the matrix of
layer-integrable material comprises an epoxy resin.
13. The hydrophobic coating of claim 12, wherein the plurality of
particles are composed of silica.
14. The hydrophobic coating of claim 11, wherein the plurality of
particles has a size distribution ranging between 1 and 50 percent
from an average size value of the plurality of particles.
15. The hydrophobic coating of claim 11, wherein the plurality of
particles has a multimodal size distribution.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a coating system used for
corrosion protection, and, in particular, relates to a method for
fabricating a hydrophobic coating system that is resistant to
corrosion.
BACKGROUND OF THE INVENTION
[0002] In a number of industries, extensive infrastructure is
installed in harsh environments. Prolonged exposure to weathering
conditions in such environment can cause structural degradation.
For example, platforms and pipes used in the oil industry in marine
environments are subject to prolonged exposure to infiltration by
salt water, which cause the surfaces of these structures to corrode
and degrade. In marine environments in particular, attempts have
been made to protect surfaces against corrosion by increasing the
water resistance (hydrophobicity) of the surfaces via the "Lotus
effect." The "Lotus effect" refers to the self-cleaning properties
of the leaves of the Lotus flower. The leaves of the Lotus flower
contain a microscopic protrusion/wax double layer that is highly
hydrophobic. As illustrated in FIG. 1, the high surface tension of
water on the Lotus leaves causes droplets to form a nearly
spherical shape with a high contact angle.
[0003] Attempts have been made to simulate the Lotus effect on
surface coatings using different approaches. One approach involves
formation of a specific morphology on a structural surface,
typically on the microscopic or nanoscopic scale. This approach
suffers from difficulties and inefficiencies in forming the
morphology in situ with nano-fabrication procedures or molds.
Accordingly, this approach is difficult to apply economically on a
large scale. A second approach involves adding a layer of particles
to a structural surface in order to provide surface roughness and
optional hierarchical structure. A significant disadvantage of the
second approach is the general lack of adhesion of the additives.
While these particle additives can be generally applied to a wide
variety of surfaces and materials with outstanding results, their
adhesion to the underlying substrate is usually not strong enough
to provide protection for longer than a relatively short duration,
e.g., several months.
[0004] There is accordingly a need for improved and cost-effective
techniques for providing anti-corrosive hydrophobic structural
coatings.
SUMMARY OF THE INVENTION
[0005] Embodiments of the present invention provide a method of
fabricating a hydrophobic coating on a surface of a solid substrate
that includes a layer-integrable material. The method includes
depositing a deformable layer of the layer-integrable material onto
the surface of the solid substrate, forcibly embedding a plurality
of particles within the deformable layer, and solidifying the
deformable layer including the plurality of particles so as to be
integral with the surface of the solid substrate. At least a
portion of the plurality of particles is embedded at a threshold
depth within the deformable layer prior to solidification.
[0006] In some embodiments, the step of forcibly embedding a
plurality of particulates within the deformable layer includes
bombarding the deformable layer with a stream of particulates at
selected momenta. In various implementation of the fabrication
method according to the present invention, each of the plurality of
particles has a size in a range of 1 nm to 50 .mu.m. In some
implementations, each of the plurality of particles has a size in
the range of 5 nm to 50 nm. In some embodiments, the distribution
of sizes of the plurality of particles can range between 1 and 50
percent from an average size value. In other embodiments, the
plurality of particles has a multimodal size distribution.
[0007] The deformable layer can be deposited in a fluid,
semi-viscous or viscous form and can comprise an epoxy resin. In
some implementations, the plurality of particles is composed of
silica. In an advantageous embodiment, upon solidification of the
deformable layer, the plurality of particles have a hierarchical
morphology such that a portion of the plurality of particles are
exposed on a surface of the solidified deformable layer, and a
portion of the plurality of particles are fully embedded within the
solidified deformable layer.
[0008] Embodiments of the present invention also provide a
hydrophobic coating that comprises a matrix of layer-integrable
material and a plurality of particles embedded at varying depths
within the matrix of layer-integrable material, wherein the
plurality of particles have a size in a range of 1 nm to 50
.mu.m.
[0009] In some embodiments, the matrix of layer-integrable material
comprises an epoxy resin. The plurality of particles can be
composed of silica. In some implementations, the hydrophobic the
plurality of particles has a size distribution ranging between 1
and 50 percent from an average size value of the plurality of
particles. In other implementations, the plurality of particles has
a multimodal size distribution.
[0010] These and other aspects, features, and advantages can be
appreciated from the following description of certain embodiments
of the invention and the accompanying drawing figures and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is perspective view showing droplets of water on a
Lotus leaf, illustrating the Lotus effect
(ultra-hydrophobicity).
[0012] FIG. 2 is a schematic illustration of a method of
fabricating a hydrophobic coating according to an embodiment of the
present invention.
[0013] FIG. 3A is a schematic illustration depicting an exemplary
deformable layer in which a unimodal distribution of particles have
been embedded according to an embodiment of the present invention.
A wide size distribution is depicted.
[0014] FIG. 3B is a schematic illustration depicting an exemplary
deformable layer in which another unimodal distribution of
particles have been embedded according to an embodiment of the
present invention. A narrow size distribution is depicted.
[0015] FIG. 3C is a schematic illustration depicting an exemplary
deformable layer in which a bimodal distribution of particles have
been embedded according to an embodiment of the present
invention.
[0016] FIG. 4 is a schematic illustration of test for measuring a
contact angle between a water droplet and a coating according to
the present invention.
[0017] FIG. 5 is a flow chart of an embodiment of a method of
fabricating a hydrophobic coating according to the present
invention.
[0018] It is noted that the drawings are illustrative and not
necessarily to scale.
DETAILED DESCRIPTION CERTAIN OF EMBODIMENTS OF THE INVENTION
[0019] By way of overview, methods for fabricating a hydrophobic
coating are disclosed herein which are suitable, among other
purposes, for protecting structures from corrosion and degradation
in harsh environments. Certain materials, such as epoxy resins have
the useful property that integral structures can be generated by
sequentially depositing and solidifying fluid or semi-fluid layers
onto one another; chemical bonding (e.g., cross-linking of polymer
chains, polymerization, crystallization) occurs between the layers
and builds up a solid, continuous matrix. The term "integral" here
indicates that there is no discontinuity between the deposited
layers of the material upon their solidification and the individual
layers become integrated into the substrate. More specifically,
bonding and/or cross-linking takes place across the boundaries of
the deposited layers and this bonding is of the same type as that
which occurs within the layers and/or substrate itself, providing
additional strength to the resulting structure. Within this
disclosure the term "layer-integrable material" or "LIM" is a term
used to denote materials having this property. Such LIM materials
are useful for fabricating corrosion-resistant coatings.
[0020] In one or more embodiments, a method of fabricating a
hydrophobic coating on a surface of a solid substrate composed of
or including a layer-integrable material comprises depositing a
deformable layer of the same layer-integrable material onto the
surface of the solid substrate, then forcibly embedding a plurality
of particles within the deformable layer, and solidifying the
deformable layer including the plurality of particles so as to be
integral with the surface of the solid substrate, wherein at least
a portion of the plurality of particles is embedded at a threshold
depth within the deformable layer prior to solidification.
[0021] FIG. 2 is a schematic block diagram that illustrates an
embodiment of the fabrication method according to the present
invention. In FIG. 2, a substrate 100, which may be a wall of a
pipe, vessel or other structure, is shown. The external surface of
the substrate 105, which is exposed to the environment, is composed
of a layer-integrable material, for example, an epoxy resin.
Suitable epoxy resins include bisphenol, aliphatic, novolac and
glycidylamine epoxy resins. Suitable curing agents that can be
included in the epoxy resins include amines, thiols, anhydrides and
phenols, and homo-polymerization improves hardening. A deformable
layer 110 of the same layer-integrable material, such as an epoxy
resin, is positioned on the surface 105 of the substrate. The
deformable layer 110 is deposited on the surface 105 in a viscous
or semi-viscous form. A spray gun or similar particle-bombardment
device 120 ("bombardment device") having a nozzle 122 directed
toward the deformable layer is shown projecting particles toward
the deformable layer 110. The bombardment device can be
pneumatically or electrostatically operated, or can be operated
based on any other suitable energy source.
[0022] The particles 125 that are projected from bombardment device
125 are microscopic and/or nanoscopic in scale. That is the largest
dimension (e.g., diameter) of the particles 125 can be in the range
of about 1 nm to about 50 .mu.m, and is preferably in the range of
about 5 to about 50 nanometers, although other particle dimensions
can be employed. The purpose of the particles is to impart surface
roughness to the deformable layer and impart hydrophobic properties
in the manner of the Lotus effect. The particle size is selected
carefully both to ensure that the surface does not become overly
fragile (when the particles are too small), and that the contact
area between the surface and the droplets does not becomes too
large, which can reduce the Lotus effect. Thus, the particle size
is selected to maximize the Lotus effect by avoiding undesirable
gaps to form and to keep the surface area between the particles and
droplets in an optimal range.
[0023] The distributions of sizes within a set of particles
selected for bombardment can also be varied to affect the resulting
morphology of the coating. In some implementations, the
distribution can be unimodal, with a central average, and variance
of sizes ranging from 1 to 50% about the average size. In other
implementations, the distribution can be multimodal (e.g., 2 to 5
distinct size distributions) with each distinct range having its
own modal average and a narrower variance, e.g., 1 to 10 percent
from each modal average. Other numbers of modes and distributional
variances can be used. The selection of size distributions provides
any way to adjust the hydrophobicity of the surface because the
roughness of the surface typically decreases with the number of
distinct size distributions, which can reduce hydrophobicity.
[0024] However, one of the advantages of multimodal size
distributions is that it allows a hierarchical structure to be
created having enhanced hydrophobicity. FIG. 3A schematically
illustrates deformable layer 205 in which a unimodal distribution
of particles 210 have been embedded according to an embodiment of
the present invention. The distribution of particles 210 varies
approximately 50% about an average (i.e., if the average is
normalized at 1.0, the size of the particles varies from 0.5 to
1.5. FIG. 3B illustrates another embodiment, depicting a deformable
layer 215 in which a different unimodal distribution of particles
220 has been embedded. In FIG. 3B, the unimodal distribution is
more narrow, in that the size of the particles vary only about 10
percent from the average (i.e., if the average is normalized at
1.0, the size of the particles varies from 0.9 to 1.1). FIG. 3C
illustrates a further embodiment, depicting a deformable layer 225
in which a bimodal distribution of particles, 226, 228 has been
embedded. The first distribution of particles 226 has an average
diameter less than half of the average diameter of the second
distribution of particles 228. Each distribution 226, 228 in the
embodiment shown in FIG. 3C various about 10 percent from the
average. FIG. 3C illustrates a hierarchical surface structure that
can be created using a multimodal particle size distribution. It is
noted that while the particles are depicted as circles in FIGS.
3A-3C, this is for purposes of convenient illustration only, and
does necessarily represent the shape of the particles, which can be
irregular.
[0025] The adhesion of the particles within the deformable layer is
selected such that a portion of the particles emitted by the
bombardment device penetrate to a threshold depth within the
deformable layer. The threshold depth can range from one-quarter of
the average diameter of the particles to approximately 100 times
the average particle diameter. This depth range can provide a
complex morphology with particles distributed throughout the depth
of the deformable layer. This is achieved by adjusting both the
viscosity of the deformable layer and the momentum of the particles
emitted by the bombardment device. With regard to the first factor,
the material of the deformable layer is adjusted to provide
sufficient fluidity for at least a portion of the particles to
reach the threshold depth. The viscosity is also adjusted to be
sufficient high to avoid having completely the particles penetrate
completely through the deformable layer to the surface of the
substrate. Thus, the factors are adjusted so that a significant
portion of the particles are exposed on the surface of the
deformable layer so as to provide surface roughness. A suitable
range for the viscosities of the deformable layer is between about
1000 and about 500,000 cP, although other viscosity levels can be
used. Such viscosities enable particles of micro to nanometer-size
to penetrate into the matrix of the deformable layer without
penetrating through to the substrate. In addition temperature
conditions are adjusted, according to the type of material used, to
ensure that the viscosity of the deformable layer is maintained
within a suitable range.
[0026] With regard to the particle bombardment, the momentum of
impact and the size of the particles are taken into account. In
particular, for the same speed of impact, and the same mass,
particles with smaller diameters tend to penetrate deeper than
particles with larger diameters. Similarly, keeping the bombardment
speed and size constant, heavier particles tend to penetrate
further than lighter ones. As a result, the viscosity of the
deformable layer is adjusted in tandem with particle bombardment
parameters to enable at least a portion of the particles to
penetrate to the desired depth. As a rule of thumb, the viscosity
is estimated to be directly proportional to the momentum of the
particles and inversely proportional to the area of impact. This
relationship can be summarized by the following equation:
V = k p a ( 1 ) ##EQU00001##
in which V is the viscosity, p is the momentum of the particles, a
is the area of impact, which is directly related to the size of the
particles, and k is a constant.
[0027] In some implementations of the present invention, epoxy
resin is used as the matrix for the deformable layer and silica is
used as the material for the particles (referred to as the
Epoxy/Silica system). Commercial Epoxy resins can be prepared by
mixing pre-polymer and a curing agent. The resins can then be
applied on the structure in fluid form using techniques known in
the art. Generally, directly after preparation, the viscosities of
such epoxy resins are in the range of about 1000 to about 3000 cP,
and within a half hour of application to a structure, the
viscosities can reach a range of about 10,000 to about 50,000 cP.
This range is suitable for the bombardment with silica
nanoparticles according to the present invention. In one specific
implementation, a bimodal distribution of particles sizes is used,
with a first distribution having sizes ranging from about 200 to
about 800 nm, and a second distribution with smaller particles
ranging from about 10 to about 100 nm. The speed of bombardment in
these conditions is on the order of the speed of simple casting and
can range from 0.1 m/s to 10 m/s according to the desired ultimate
depth of the particles within the deformable layer.
[0028] Once the nanoparticles have been embedded into the coating
the deformable layer can be cured and solidified. Due to the fact
that particles are bombarded to penetrate at various depths, upon
solidification, a hierarchical morphology is thus frozen in place.
The hierarchical morphology gives the coatings fabricated according
to the present invention a significant advantage in that the
coating can retain hydrophobicity and surface roughness even after
a certain amount of corrosion and surface wear. This is because as
the exposed layers of the particles on the surface are worn away,
the particles embedded beneath are in turn exposed to the surface,
and provide a commensurate level of surface roughness and
hydrophobicity to the coating.
[0029] Coatings fabricated according to the present invention can
achieve a contact angle (the angle (a) at which a water droplet
contacts a surface) averaging as high as 150 degrees, in the
ultra-hydrophobic range. FIG. 4 is a schematic illustration of a
test for measuring a contact angle between a water droplet and a
coating according to the present invention. As depicted, the
contact angle (a) between water droplet 410 and coating 415 is
approximately 150 degrees.
[0030] One of the main advantages of the fabrication methods of the
present invention is their general applicability. Since the methods
do not require modification of an already existing coating (i.e.,
substrate), they can be readily used in existing installations.
This makes the methods particularly economically attractive to
employ. One notable application is protection of metallic
structures exposed to harsh marine environments from corrosion.
Such metal structures can be coated initially using
commercially-available epoxy paints including Hempadur 45070,
Interseal 41/Interzone 954, Jotamastic 80/Penguard FC, Sigmacover
410 prime/Sigmacover 410, Carboguard 690, and Euronavy ES301. To
this paint can be added a coating according to the present
invention as described. The coating provides additional surface
roughness sufficient to achieve high hydrophobicity while only
minimally modifying the structure and the integrity of the
underlying paint and substrate. Since the particles are added on
the surface of the coating when the polymeric coating is still not
completely cured, the particles are incorporated in proximity of
the surface of the coating.
[0031] Further enhancements can be made to properties of the
coating fabricated according to the present invention through use
of additives. For example, hydrophobic ligands can be added to the
silica particles. These ligands add an additional chemical
hydrophobic barrier. The choices of the ligands can be diverse. For
instance, fluorinated silane can be added to silica nanoparticles.
The fluorinated chemical groups promote hydrophobicity and the
silane groups can be bonded to the silica through silanization, as
known in the art.
[0032] FIG. 5 is a flow chart of an embodiment of a method of
fabricating a hydrophobic coating on a surface of a solid substrate
including a layer-integrable material according to the present
invention. In step 500 the method begins with selection of a
substrate (or initial coating) including a layer-integrable
material that is to be protected with an anti-corrosion coating. In
step 502, a deformable viscous or semi-viscous layer of
layer-integrable material is deposited onto the substrate. In step
504, particles are forcibly embedded (e.g., by bombardment) into
the deformable layer at selected momenta and are embedded in the
deformable layer at varying depths. In step 506, the deformable
layer is solidified and is integrated seamlessly and continuously
with the substrate.
[0033] Although the disclosed methods were described mainly with
reference to epoxy coating and silica particles, other materials
that are layer-integrable as defined above can be used. Such
layer-integrable materials can include polymer resins such as
polyurethanes, polysiloxanes, polyacrylates, polyethylene,
polypropylene, polystyrene, etc. Additionally, alternative particle
materials that can employed include zinc oxide, manganese oxide,
calcium carbonate, carbon Nanotubes, graphene oxide, magnesium
oxide, among other oxides or sulfides.
[0034] It is to be understood that any structural and functional
details disclosed herein are not to be interpreted as limiting the
systems and methods, but rather are provided as a representative
embodiment and/or arrangement for teaching one skilled in the art
one or more ways to implement the methods.
[0035] It should be understood that although much of the foregoing
description has been directed to systems and methods for implanting
photonic materials, methods disclosed herein can be similarly
deployed other `smart` structures in scenarios, situations, and
settings beyond the referenced scenarios. It should be further
understood that any such implementation and/or deployment is within
the scope of the system and methods described herein.
[0036] It is to be further understood that like numerals in the
drawings represent like elements through the several figures, and
that not all components and/or steps described and illustrated with
reference to the figures are required for all embodiments or
arrangements
[0037] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. 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. It will be further understood
that the terms "comprises" and/or "comprising", when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, 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.
[0038] Terms of orientation are used herein merely for purposes of
convention and referencing, and are not to be construed as
limiting. However, it is recognized these terms could be used with
reference to a viewer. Accordingly, no limitations are implied or
to be inferred.
[0039] Also, the phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. The
use of "including," "comprising," or "having," "containing,"
"involving," and variations thereof herein, is meant to encompass
the items listed thereafter and equivalents thereof as well as
additional items.
[0040] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications will be
appreciated by those skilled in the art to adapt a particular
instrument, situation or material to the teachings of the invention
without departing from the essential scope thereof. Therefore, it
is intended that the invention not be limited to the particular
embodiment disclosed as the best mode contemplated for carrying out
this invention, but that the invention will include all embodiments
falling within the scope of the appended claims.
* * * * *