[0001] This application relates to material deposition onto substrates and, more particularly,
to compositions and methods for activating metallic substrates and compositions and
methods for electrodepositing tin-bismuth alloys onto metallic substrates.
[0002] Mechanical fasteners are widely used for joining two or more components of a structural
assembly. For example, mechanical fasteners are extensively used for joining the structural
components of the airframe of an aircraft.
[0003] Aircraft experience electromagnetic effects (EME) from a variety of sources, such
as lightning strikes and precipitation static. Metallic aircraft structures are readily
conductive and, therefore, are relatively less susceptible to electromagnetic effects.
However, composite (e.g., carbon fiber reinforced plastic) aircraft structures do
not readily conduct away the significant electrical currents and electromagnetic forces
stemming from electromagnetic effects. Therefore, when mechanical fasteners are used
in composite aircraft structures, steps must be taken to protect against electromagnetic
effects.
[0004] Electromagnetic effects protection can be provided to mechanical fasteners in the
form of an electrically conductive metallic surface deposit, such as metallic plating.
While various metallic surface deposits may provide suitable electrical conductivity
for imparting electromagnetic effects protection, other factors, such as lubricity
and galvanic compatibility with carbon fiber-reinforced plastics, are also considerations
for mechanical fasteners intended for the aerospace industry.
[0005] Tin exists in alpha and beta phases. Alpha tin is grey in color, powdery and forms
pest, while beta tin is white and possesses body centered tetragonal crystal structure.
When tin is alloyed with bismuth at concentrations greater than 0.4 percent by weight
bismuth, it begins to exist as beta phase. Tin-bismuth has shown promise as a suitable
metallic surface deposit for mechanical fasteners due to its electrical conductivity,
lubricity and galvanic compatibility with carbon fiber-reinforced plastics.
[0006] Accordingly, those skilled in the art continue with research and development efforts
in the field of electrodeposition.
[0007] Embodiments herein include:
An activation solution including water, an ammonium salt having a fluorine-containing
anion, and sulfuric acid.
[0008] An activation solution including water, ammonium bifluoride and/or ammonium tetrafluoroborate
dissolved in the water, and sulfuric acid dissolved in the water.
[0009] An activation solution including water, ammonium bifluoride and/or ammonium tetrafluoroborate
dissolved in the water at a concentration ranging from about 10 grams per liter to
about 150 grams per liter, based on a total volume of the activation solution, and
sulfuric acid dissolved in the water at a concentration ranging from about 1 percent
by volume to about 70 percent by volume, based on a total volume of the activation
solution.
[0010] An activation solution including water, ammonium bifluoride dissolved in the water
at a concentration ranging from about 20 grams per liter to about 120 grams per liter,
based on a total volume of the activation solution, and sulfuric acid dissolved in
the water at a concentration ranging from about 5 percent by volume to about 25 percent
by volume, based on a total volume of the activation solution.
[0011] A method for manufacturing an activation solution includes steps of (1) mixing sulfuric
acid with water to yield an acidic solution and (2) dissolving an ammonium salt in
the acidic solution, the ammonium salt having a fluorine-containing anion.
[0012] A method for pretreating a substrate prior to depositing a material thereon, the
method including the step of immersing the substrate in an activation solution for
a predetermined period of time or predetermined period of time, the activation solution
including water, an ammonium salt dissolved in the water, the ammonium salt having
a fluorine-containing anion, and sulfuric acid dissolved in the water.
[0013] Other expressions of the disclosed compositions and methods for activating metallic
substrates will become apparent from the following detailed description, the accompanying
drawings and the appended claims.
Fig. 1 is a flow diagram depicting a disclosed method for depositing a material onto
a substrate;
Fig. 2 is micrograph of a tin-bismuth alloy deposited on a titanium substrate in accordance
with the method of Fig. 1;
Fig. 3 is a flow diagram depicting one disclosed method for activating a substrate,
such as a titanium substrate, in accordance with the method of Fig. 1;
Fig. 4 is a schematic illustration of a system for activating a substrate in accordance
with the method of Fig. 3;
Fig. 5 is a flow diagram depicting another disclosed method for activating a substrate,
such as a titanium substrate, in accordance with the method of Fig. 1;
Fig. 6 is a schematic illustration of a system for activating a substrate in accordance
with the method of Fig. 5;
Fig. 7 is a flow diagram depicting yet another disclosed method for activating a substrate,
such as a titanium substrate, in accordance with the method of Fig. 1;
Fig. 8 is a schematic illustration of a system for activating a substrate in accordance
with the method of Fig. 7;
Fig. 9 is a schematic illustration of a system for strike plating a substrate in accordance
with the method of Fig. 1;
Fig. 10 is a flow diagram depicting one disclosed method for electrodepositing a tin-bismuth
alloy onto a substrate in accordance with the method of Fig. 1;
Fig. 11 is a schematic illustration of an electrodeposition system for depositing
a tin-bismuth alloy in accordance with the method of Fig. 10;
Fig. 12 is a flow diagram of an aircraft manufacturing and service methodology; and
Fig. 13 is a block diagram of an aircraft.
[0014] Disclosed are compositions, systems and methods for activating a metallic substrate,
such as a metallic fastener or other part/component. Also disclosed are compositions,
systems and methods for depositing a material onto a metallic substrate, such as a
metallic fastener or other part/component. The disclosed compositions, systems and
methods may be used separately or in various combinations to achieve the desired material
deposit on a substrate.
[0015] Referring to Fig. 1, disclosed is a method, generally designated 10, for depositing
a material onto a substrate. While only three general steps are shown, those skilled
in the art will appreciate that various additional steps may be performed whether
before, after or between the presented steps-without resulting in a departure from
the scope of the present disclosure.
[0016] The initial step (Block 12) of method 10 includes pre-treating the substrate to render
the substrate suitable for receiving thereon a material, such as a metallic deposit
or other metallic/non-metallic material. Various pre-treatments may be performed,
such as cleaning, degreasing, etching and the like. In particular, the pre-treating
step (Block 12) may include activating (Block 14) the surface of the substrate. For
example, in the case of titanium substrates, the step of activating (Block 14) the
surface of the substrate may remove (or at least substantially reduce) the tenacious
oxide layer that is known to form thereon.
[0017] The intermediate step (Block 16) of method 10 includes strike plating the pre-treated
substrate. The step of strike plating (Block 16) the surface of the substrate may
form a thin metallic layer on the surface of the substrate, thereby providing the
substrate with a surface more suitable for receiving and bonding with a subsequent
metallic deposit. In a particular implementation, the strike plating step (Block 16)
may form a thin layer of nickel on the surface of the substrate.
[0018] The final step (Block 18) of method 10 includes electrodeposition onto the strike-plated
substrate. The electrodeposition step (Block 18) may form a metallic deposit on the
surface of the substrate. In a particular implementation, the electrodeposition step
(Block 18) may deposit a tin-bismuth alloy on the surface of the substrate.
[0019] Referring to Fig. 2, the disclosed method 10 was used to deposit a thin layer of
a tin-bismuth alloy onto the surface of a titanium alloy (Ti-6A1-4V) substrate. The
result was an excellent bond between the tin-bismuth alloy deposit and the underlying
titanium alloy substrate.
[0020] While the present disclosure primarily focuses on titanium substrates-substrates
formed from titanium or titanium alloys, such as Ti-6A1-4V, it is believed that the
disclosed method 10, as well as individual steps of the disclosed method 10 (e.g.,
the activating step (Block 14), the strike plating step (Block 16) and/or the electrodeposition
step (Block 18)) may be suitable for non-titanium substrates. Examples of non-titanium
substrates that may benefit from the present disclosure include, without limitation,
iron alloys, copper alloys and nickel alloys (e.g., Inconel).
ACTIVATION
[0021] Disclosed are three activation methods, including associated compositions and systems.
A metallic substrate, such as a titanium substrate, may be activated using just one
of the disclosed activation methods. Alternatively, a metallic substrate, such as
a titanium substrate, may be activated using multiple activation methods (e.g., a
sequence of activation methods), including one or more of the disclosed activation
methods.
[0022] Referring to Figs. 3 and 4, a first activation method, generally designated 100,
may begin at Block 110 (Fig. 3) with the step of preparing a bath 152 containing an
activation solution 154, as shown in Fig. 4. The bath 152 and the activation solution
154 may comprise the first activation system 150.
[0023] The bath 152 may be any vessel suitable for receiving and containing the activation
solution 154. Compositionally, the material forming the bath 152 should be chemically
compatible with the activation solution 154. Of course, the bath 152 should be sized
and shaped to be able to receive therein the substrate 156 to be activated by the
first activation system 150.
[0024] The activation solution 154 includes water (H2O), an ammonium salt dissolved in the
water, and sulfuric acid (H
2SO
4) dissolved in the water. The activation solution 154 may be maintained at atmospheric
pressure (e.g., 1 atm) and at a temperature between about 15 °C and about 50 °C (e.g.,
room temperature (∼21 °C)). However, using higher and lower pressures, and higher
and lower temperatures is contemplated, and will not result in a departure from the
scope of the present disclosure.
[0025] The ammonium salt in the activation solution 154 may have a fluorine-containing anion.
In one formulation, the ammonium salt in the activation solution 154 is ammonium bifluoride
(NH
4HF
2). In another formulation, the ammonium salt in the activation solution 154 is ammonium
tetrafluoroborate (NH
4BF
4). In yet another formulation, the ammonium salt in the activation solution 154 includes
both ammonium bifluoride (NH
4HF
2) and ammonium tetrafluoroborate (NH
4BF
4).
[0026] The ammonium salt in the activation solution 154 may be present at a concentration
ranging from about 10 grams per liter to about 150 grams per liter, based on the total
volume of the activation solution 154. In one alternative expression, the ammonium
salt concentration ranges from about 20 grams per liter to about 120 grams per liter,
based on the total volume of the activation solution 154. In another alternative expression,
the ammonium salt concentration ranges from about 30 grams per liter to about 110
grams per liter, based on the total volume of the activation solution 154. In another
alternative expression, the ammonium salt concentration ranges from about 40 grams
per liter to about 100 grams per liter, based on the total volume of the activation
solution 154. In another alternative expression, the ammonium salt concentration ranges
from about 50 grams per liter to about 100 grams per liter, based on the total volume
of the activation solution 154. In another alternative expression, the ammonium salt
concentration ranges from about 60 grams per liter to about 100 grams per liter, based
on the total volume of the activation solution 154. In another alternative expression,
the ammonium salt concentration ranges from about 70 grams per liter to about 90 grams
per liter, based on the total volume of the activation solution 154. In yet alternative
expression, the ammonium salt concentration is about 80 grams per liter, based on
the total volume of the activation solution 154.
[0027] The sulfuric acid in the activation solution 154 may be present at a concentration
ranging from about 1 percent by volume to about 70 percent by volume, based on the
total volume of the activation solution 154. In one alternative expression, the sulfuric
acid concentration ranges from about 2 percent by volume to about 50 percent by volume,
based on the total volume of the activation solution 154. In another alternative expression,
the sulfuric acid concentration ranges from about 3 percent by volume to about 40
percent by volume, based on the total volume of the activation solution 154. In another
alternative expression, the sulfuric acid concentration ranges from about 4 percent
by volume to about 30 percent by volume, based on the total volume of the activation
solution 154. In another alternative expression, the sulfuric acid concentration ranges
from about 5 percent by volume to about 25 percent by volume, based on the total volume
of the activation solution 154. In another alternative expression, the sulfuric acid
concentration ranges from about 5 percent by volume to about 15 percent by volume,
based on the total volume of the activation solution 154. In yet another alternative
expression, the sulfuric acid concentration is about 10 percent by volume, based on
the total volume of the activation solution 154.
[0028] As one specific, non-limiting example, the activation solution 154 includes water,
80 grams per liter ammonium bifluoride (NH
4HF
2), and 10 percent by volume sulfuric acid (H
2SO
4).
[0029] The activation solution 154 may be manufactured in various ways without departing
from the scope of the present disclosure. In one particular implementation, the disclosed
method for manufacturing the activation solution 154 includes steps of (1) mixing
sulfuric acid (e.g., 66 degree Baume sulfuric acid) with at least a portion of the
water (e.g., deionized water) to yield an acidic solution, (2) dissolving an ammonium
salt (e.g., ammonium bifluoride and/or ammonium tetrafluoroborate) in the acidic solution;
and (3) adding additional water, if needed, to make up the required total volume of
the activation solution 154.
[0030] At Block 120 (Fig. 3), the substrate 156 is immersed (e.g., completely immersed)
in the activation solution 154. The substrate 156 may remain immersed in the activation
solution 154 for a predetermined period of time prior to removing the substrate 156
from the activation solution 154, as shown in Block 130 (Fig. 3). In the case of titanium
substrates (substrate 156), the predetermined period of time may be selected such
that the activation solution 154 has sufficient time to reduce/eliminate the tenacious
oxide layer on the substrate 156 without significantly disturbing the titanium/titanium
alloy underlying the oxide layer. In one expression, the predetermined period of time
is about 5 seconds to about 120 seconds. In another expression, the predetermined
period of time is about 10 seconds to about 100 seconds. In another expression, the
predetermined period of time is about 20 seconds to about 40 seconds. In yet another
expression, the predetermined period of time is about 30 seconds.
[0031] At Block 140 (Fig. 3), the substrate 156 removed from the activation solution 154
may be rinsed with a rinsing fluid. As an example, the rinsing fluid may be water,
such as deionized water.
[0032] Referring to Figs. 5 and 6, a second activation method, generally designated 200,
may begin at Block 202 (Fig. 5) with the step of preparing a bath 252 containing an
activation solution 254, as shown in Fig. 6. The bath 252 and the activation solution
254 may comprise the second activation system 250.
[0033] The bath 252 may be any vessel suitable for receiving and containing the activation
solution 254. Compositionally, the material forming the bath 252 should be chemically
compatible with the activation solution 254. Of course, the bath 252 should be sized
and shaped to be able to receive therein the substrate 256 to be activated by the
second activation system 250.
[0034] The activation solution 254 includes water (H
2O), a fluoride salt dissolved in the water, hydrofluoric acid (HF) dissolved in the
water, and sulfuric acid (H
2SO
4) dissolved in the water. The activation solution 254 may be maintained at atmospheric
pressure (e.g., 1 atm) and at a temperature between about 15 °C and about 50 °C (e.g.,
room temperature (∼21 °C)). However, using higher and lower pressures, and higher
and lower temperatures is contemplated, and will not result in a departure from the
scope of the present disclosure.
[0035] The fluoride salt in the activation solution 254 may have an alkali metal cation
and/or an alkaline earth metal cation. In one formulation, the fluoride salt in the
activation solution 254 is potassium fluoride (KF). In another formulation, the fluoride
salt in the activation solution 254 is lithium fluoride (LiF). In another formulation,
the fluoride salt in the activation solution 254 is sodium fluoride (NaF). In another
formulation, the fluoride salt in the activation solution 254 is rubidium fluoride
(RuF). In another formulation, the fluoride salt in the activation solution 254 is
barium fluoride (BaF
2). In another formulation, the fluoride salt in the activation solution 254 is strontium
fluoride (SrF
2). In yet another formulation, the fluoride salt in the activation solution 254 includes
at least two of potassium fluoride (KF), lithium fluoride (LiF), sodium fluoride (NaF),
rubidium fluoride (RuF), barium fluoride (BaF
2), and strontium fluoride (SrF
2).
[0036] The fluoride salt in the activation solution 254 may be present at a concentration
ranging from about 5 grams per liter to about 120 grams per liter, based on the total
volume of the activation solution 254. In one alternative expression, the fluoride
salt concentration ranges from about 10 grams per liter to about 100 grams per liter,
based on the total volume of the activation solution 254. In another alternative expression,
the fluoride salt concentration ranges from about 15 grams per liter to about 75 grams
per liter, based on the total volume of the activation solution 254. In another alternative
expression, the fluoride salt concentration ranges from about 15 grams per liter to
about 50 grams per liter, based on the total volume of the activation solution 254.
In another alternative expression, the fluoride salt concentration ranges from about
15 grams per liter to about 30 grams per liter, based on the total volume of the activation
solution 254. In yet alternative expression, the fluoride salt concentration is about
20 grams per liter, based on the total volume of the activation solution 254.
[0037] The hydrofluoric acid in the activation solution 254 may be present at a concentration
ranging from about 5 milliliters per liter to about 250 milliliters per liter, based
on the total volume of the activation solution 254. In one alternative expression,
the hydrofluoric acid concentration ranges from about 10 milliliters per liter to
about 200 milliliters per liter, based on the total volume of the activation solution
254. In another alternative expression, the hydrofluoric acid concentration ranges
from about 15 milliliters per liter to about 150 milliliters per liter, based on the
total volume of the activation solution 254. In another alternative expression, the
hydrofluoric acid concentration ranges from about 20 milliliters per liter to about
150 milliliters per liter, based on the total volume of the activation solution 254.
In another alternative expression, the hydrofluoric acid concentration ranges from
about 30 milliliters per liter to about 100 milliliters per liter, based on the total
volume of the activation solution 254. In another alternative expression, the hydrofluoric
acid concentration ranges from about 40 milliliters per liter to about 80 milliliters
per liter, based on the total volume of the activation solution 254. In yet another
alternative expression, the hydrofluoric acid concentration is about 60 milliliters
per liter, based on the total volume of the activation solution 254.
[0038] The sulfuric acid in the activation solution 254 may be present at a concentration
ranging from about 1 percent by volume to about 45 percent by volume, based on the
total volume of the activation solution 254. In one alternative expression, the sulfuric
acid concentration ranges from about 2 percent by volume to about 35 percent by volume,
based on the total volume of the activation solution 254. In another alternative expression,
the sulfuric acid concentration ranges from about 2 percent by volume to about 20
percent by volume, based on the total volume of the activation solution 254. In another
alternative expression, the sulfuric acid concentration ranges from about 3 percent
by volume to about 15 percent by volume, based on the total volume of the activation
solution 254. In another alternative expression, the sulfuric acid concentration ranges
from about 3 percent by volume to about 10 percent by volume, based on the total volume
of the activation solution 254. In yet another alternative expression, the sulfuric
acid concentration is about 5 percent by volume, based on the total volume of the
activation solution 254.
[0039] As one specific, non-limiting example, the activation solution 254 includes water,
20 grams per liter potassium fluoride (KF), 60 milliliters per liter hydrofluoric
acid (HF), and 5 percent by volume sulfuric acid (H
2SO
4).
[0040] The activation solution 254 may be manufactured in various ways without departing
from the scope of the present disclosure. In one particular implementation, the disclosed
method for manufacturing the activation solution 254 includes steps of (1) mixing
sulfuric acid (e.g., 66 degree Baume sulfuric acid) with water (e.g., deionized water)
to yield a first acidic solution, (2) mixing hydrofluoric acid (e.g., 48 wt% in water)
with the first acidic solution to yield a second acidic solution, (3) dissolving a
fluoride salt (e.g., potassium fluoride) in the second acidic solution; and (4) adding
additional water, if needed, to make up the required total volume of the activation
solution 254.
[0041] At Block 204 (Fig. 5), the substrate 256 is immersed (e.g., completely immersed)
in the activation solution 254. The substrate 256 may remain immersed in the activation
solution 254 for a predetermined period of time prior to removing the substrate 256
from the activation solution 254, as shown in Block 206 (Fig. 5). In the case of titanium
substrates (substrate 256), the predetermined period of time may be selected such
that the activation solution 254 has sufficient time to reduce/eliminate the tenacious
oxide layer on the substrate 256 without significantly disturbing the titanium/titanium
alloy underlying the oxide layer. In one expression, the predetermined period of time
is about 5 seconds to about 120 seconds. In another expression, the predetermined
period of time is about 10 seconds to about 100 seconds. In another expression, the
predetermined period of time is about 20 seconds to about 40 seconds. In yet another
expression, the predetermined period of time is about 30 seconds.
[0042] At Block 208 (Fig. 5), the substrate 256 removed from the activation solution 254
may be rinsed with a rinsing fluid. As an example, the rinsing fluid may be water,
such as deionized water.
[0043] Referring to Figs. 7 and 8, a third activation method, generally designated 300,
may begin at Block 302 (Fig. 7) with the step of preparing a bath 352 containing an
activation solution 354, as shown in Fig. 8. The bath 352 and the activation solution
354, together with a graphite electrode 358 and current source 360, may comprise the
third activation system 350, which may be used to perform an anodic sulfuric acid
method (third activation method 300), as is described herein.
[0044] The bath 352 may be any vessel suitable for receiving and containing the activation
solution 354. Compositionally, the material forming the bath 352 should be chemically
compatible with the activation solution 354. Of course, the bath 352 should be sized
and shaped to be able to receive therein the graphite anode 358 and the substrate
356 to be activated by the third activation system 350.
[0045] The activation solution 354 includes water (H
2O) and sulfuric acid (H
2SO
4) dissolved in the water. The activation solution 354 may be maintained at atmospheric
pressure (e.g., 1 atm) and at a temperature between about 15 °C and about 50 °C (e.g.,
room temperature (∼21 °C)). However, using higher and lower pressures, and higher
and lower temperatures is contemplated, and will not result in a departure from the
scope of the present disclosure.
[0046] The sulfuric acid in the activation solution 354 may be present at a concentration
ranging from about 5 percent by volume to about 45 percent by volume, based on the
total volume of the activation solution 354. In one alternative expression, the sulfuric
acid concentration ranges from about 5 percent by volume to about 35 percent by volume,
based on the total volume of the activation solution 354. In another alternative expression,
the sulfuric acid concentration ranges from about 5 percent by volume to about 30
percent by volume, based on the total volume of the activation solution 354. In another
alternative expression, the sulfuric acid concentration ranges from about 5 percent
by volume to about 25 percent by volume, based on the total volume of the activation
solution 354. In another alternative expression, the sulfuric acid concentration ranges
from about 10 percent by volume to about 20 percent by volume, based on the total
volume of the activation solution 254. In yet another alternative expression, the
sulfuric acid concentration is about 15 percent by volume, based on the total volume
of the activation solution 354.
[0047] As one specific, non-limiting example, the activation solution 354 includes water
and 15 percent by volume sulfuric acid (H
2SO
4).
[0048] At Block 304 (Fig. 7), the substrate 356 is immersed (e.g., completely immersed)
in the activation solution 354. A lead 368 may electrically couple the immersed substrate
356 with a first terminal 364 of the current source 360.
[0049] At Block 306 (Fig. 7), the graphite electrode 358 is immersed (e.g., completely immersed)
in the activation solution 354. A lead 366 may electrically couple the immersed graphite
electrode 358 with a second terminal 362 of the current source 360.
[0050] At Block 308 (Fig. 7), the current source 360 is actuated such that an electric current
is passed between the substrate 356 and the graphite electrode 358. The current source
360 may be configured such that the substrate 356 functions as the anode, thereby
etching the substrate 356. In the case of titanium substrates (substrate 356), the
anodic sulfuric acid method (third activation method 300) may reduce/eliminate the
tenacious oxide layer on the substrate 356 without significantly disturbing the titanium/titanium
alloy underlying the oxide layer.
[0051] The step of passing an electric current (Block 308) may be performed at various current
densities without departing from the scope of the present disclosure. Those skilled
in the art will appreciate that current density is a controllable parameter, and selection
of an appropriate current density may require consideration of various factors, such
as the duration of the passing step (Block 308), among other factors. In one expression,
the electric current passed during the passing step (Block 308) may have a current
density ranging from about 10 amperes per square foot to about 80 amperes per square
foot, based on the surface area of the substrate 356. In another expression, the electric
current passed during the passing step (Block 308) may have a current density ranging
from about 20 amperes per square foot to about 60 amperes per square foot, based on
the surface area of the substrate 356. In another expression, the electric current
passed during the passing step (Block 308) may have a current density ranging from
about 20 amperes per square foot to about 40 amperes per square foot, based on the
surface area of the substrate 356. In yet another expression, the electric current
passed during the passing step (Block 308) may have a current density of about 30
amperes per square foot, based on the surface area of the substrate 356.
[0052] The step of passing an electric current (Block 308) may be performed for various
durations of time without departing from the scope of the present disclosure. Those
skilled in the art will appreciate that the current duration is a controllable parameter,
and selection of an appropriate duration of time may require consideration of various
factors, such as the current density, among other factors. In one expression, the
passing step (Block 308) may be performed for about 5 seconds to about 120 seconds.
In another expression, the passing step (Block 308) may be performed for about 10
seconds to about 100 seconds. In another expression, the passing step (Block 308)
may be performed for about 10 seconds to about 60 seconds. In another expression,
the passing step (Block 308) may be performed for about 15 seconds to about 45 seconds.
In yet another expression, the passing step (Block 308) may be performed for about
20 seconds to about 30 seconds.
[0053] At Block 310 (Fig. 7), the substrate 356 is disconnected from the current source
360 and removed from the activation solution 354.
[0054] At Block 312 (Fig. 7), the substrate 356 may be rinsed with a rinsing fluid. As an
example, the rinsing fluid may be water, such as deionized water.
STRIKE PLATING
[0055] Various strike plating processes, including nickel strike plating processes (e.g.,
Wood's nickel strike) are known in the art, and may be used in the method 10 of Fig.
1 without departing from the scope of the present disclosure. However, disclosed is
a particular nickel strike plating method that yielded an excellent substrate-to-subsequent
plating bond, as shown in Fig. 2.
[0056] Referring to Fig. 9, a strike plating system, generally designated 450, includes
a bath 452, an electrolyte solution 454 received in the bath 452, a nickel anode 458
immersed in the electrolyte solution 454, and current source 460. The current source
460 may include first terminal 462 and a second terminal 464. The nickel anode 458
may be electrically coupled with the second terminal 464 by way of a lead 468.
[0057] The bath 452 may be any vessel suitable for receiving and containing the electrolyte
solution 454. Compositionally, the material forming the bath 452 should be chemically
compatible with the electrolyte solution 454. Of course, the bath 452 should be sized
and shaped to be able to receive therein the substrate 456 and the nickel anode 458.
[0058] The electrolyte solution 454 includes water (H2O), nickel chloride (NiCl
2) dissolved in the water, and hydrochloric acid (HCl) dissolved in the water. The
electrolyte solution 454 may be maintained at atmospheric pressure (e.g., 1 atm) and
at a temperature between about 15 °C and about 50 °C (e.g., room temperature (∼21
°C)). However, using higher and lower pressures, and higher and lower temperatures
is contemplated, and will not result in a departure from the scope of the present
disclosure.
[0059] The nickel chloride in the electrolyte solution 454 may be present at a concentration
ranging from about 50 grams per liter to about 400 grams per liter, based on the total
volume of the activation solution 354. In one alternative expression, the nickel chloride
concentration ranges from about 75 grams per liter to about 350 grams per liter, based
on the total volume of the activation solution 354. In another alternative expression,
the nickel chloride concentration ranges from about 100 grams per liter to about 300
grams per liter, based on the total volume of the activation solution 354. In another
alternative expression, the nickel chloride concentration ranges from about 125 grams
per liter to about 275 grams per liter, based on the total volume of the activation
solution 354. In another alternative expression, the nickel chloride concentration
ranges from about 150 grams per liter to about 250 grams per liter, based on the total
volume of the activation solution 354. In another alternative expression, the nickel
chloride concentration ranges from about 175 grams per liter to about 225 grams per
liter, based on the total volume of the activation solution 354.
[0060] The hydrochloric acid in the electrolyte solution 454 may be present at a concentration
ranging from about 25 milliliters per liter to about 300 milliliters per liter, based
on the total volume of the electrolyte solution 454. In one alternative expression,
the hydrochloric acid concentration ranges from about 50 milliliters per liter to
about 250 milliliters per liter, based on the total volume of the electrolyte solution
454. In another alternative expression, the hydrochloric acid concentration ranges
from about 75 milliliters per liter to about 225 milliliters per liter, based on the
total volume of the electrolyte solution 454. In another alternative expression, the
hydrochloric acid concentration ranges from about 100 milliliters per liter to about
200 milliliters per liter, based on the total volume of the electrolyte solution 454.
In another alternative expression, the hydrochloric acid concentration ranges from
about 125 milliliters per liter to about 175 milliliters per liter, based on the total
volume of the electrolyte solution 454.
[0061] As one specific, non-limiting example, the electrolyte solution 454 includes water,
200 grams per liter nickel chloride (NiCl
2) and 150 milliliters per limiter hydrochloric acid (HCl).
[0062] As shown in Fig. 9, the substrate 456 is immersed (e.g., completely immersed) in
the electrolyte solution 454 in the bath 452. Then, the substrate 456 is electrically
coupled with the first terminal 462 of the current source 460 by way of a lead 466.
[0063] To begin strike plating, the current source 460 is actuated such that an electric
current is passed between the substrate 456 and the nickel anode 458, and a deposit
forms on the substrate 456. Optionally, prior to initiating a cathodic strike, an
anodic strike (substrate 456 functions as the anode) may be performed to etch the
substrate 456.
[0064] The anodic strike (etching) may be performed at various current densities and durations
of time without departing from the scope of the present disclosure. In one expression,
the anodic strike may be performed at a current density ranging from about 25 amperes
per square foot to about 75 amperes per square foot, based on the surface area of
the substrate 456, for a duration ranging from about 1 second to about 30 seconds.
For example, the anodic strike may be performed at a current density of about 120
amperes per square foot, based on the surface area of the substrate 456, for about
10 seconds.
[0065] The cathodic strike (strike plating) may be performed at various current densities
and durations of time without departing from the scope of the present disclosure.
In one expression, the cathodic strike may be performed at a current density ranging
from about 80 amperes per square foot to about 160 amperes per square foot, based
on the surface area of the substrate 456, for a duration ranging from about 30 seconds
to about 10 minutes. For example, the cathodic strike may be performed at a current
density of about 120 amperes per square foot, based on the surface area of the substrate
456, for about 5 minutes.
[0066] Once the current source 460 is deactivated, the substrate 456 can be disconnected
from the current source 460 and removed from the electrolyte solution 454. Then, the
substrate 356 may be rinsed with a rinsing fluid, such as deionized water.
ELECTRODEPOSITION
[0067] Various strike electrodeposition processes may be used in the method 10 of Fig. 1
without departing from the scope of the present disclosure. However, disclosed is
a particular tin-bismuth electrodeposition method that yielded an excellent substrate-to-subsequent
plating bond, as shown in Fig. 2, when used in sequence with one of the disclosed
activation methods and the disclosed nickel strike plating method.
[0068] Referring to Figs. 10 and 11, the disclosed electrodeposition method, generally designated
500, may begin at Block 502 (Fig. 10) with the step of preparing a bath 552 containing
an electrolyte solution 554, as shown in Fig. 11. The bath 552 and the activation
solution 554, together with an anode 558 and a current source 560, may comprise the
disclosed electrodeposition system 550, which may be used to deposit a tin-bismuth
alloy onto a substrate 556.
[0069] The substrate 556 may be a titanium substrate, such as a titanium mechanical fastener
or the like. Other metallic substrates 556, such as iron substrates, copper substrates
and nickel substrates (e.g., Inconel), may also be used with the disclosed electrodeposition
method 500 and system 550 without departing from the scope of the present disclosure.
[0070] The anode 558 of the disclosed electrodeposition system 550 may be a tin anode (e.g.,
99.99 percent pure tin) or a tin-bismuth anode. As one general example, the anode
558 may include about 2 percent by weight to about 5 percent by weight bismuth, with
the balance substantially tin. As one specific example, the anode 558 may include
about 3 percent by weight bismuth, with the balance substantially tin.
[0071] The bath 552 may be any vessel suitable for receiving and containing the electrolyte
solution 554. Compositionally, the material forming the bath 552 should be chemically
compatible with the activation solution 554. Of course, the bath 552 should be sized
and shaped to be able to receive therein the anode 558 and the substrate 556.
[0072] The electrolyte solution 554 includes water (H2O), a stannous salt dissolved in the
water, a bismuth salt dissolved in the water, and an acid. The electrolyte solution
554 may be maintained at atmospheric pressure (e.g., 1 atm) and at a temperature between
about 15 °C and about 50 °C (e.g., room temperature (∼21 °C)). However, using higher
and lower pressures, and higher and lower temperatures is contemplated, and will not
result in a departure from the scope of the present disclosure.
[0073] The stannous salt in the electrolyte solution 554 provides stannous (tin(II)
2+) ions. In one formulation, the stannous salt in the electrolyte solution 554 is stannous
sulfate (SnSO
4). In another formulation, the stannous salt in the electrolyte solution 554 is stannous
chloride (SnCl
2). In another formulation, the stannous salt in the electrolyte solution 554 is stannous
fluoride (SnF
2). In yet another formulation, the stannous salt in the electrolyte solution 554 includes
at least two of stannous sulfate (SnSO
4), stannous chloride (SnCl
2), and stannous fluoride (SnF
2).
[0074] The stannous salt in the electrolyte solution 554 may be present at a concentration
ranging from about 15 grams per liter to about 200 grams per liter, based on the total
volume of the electrolyte solution 554. In one alternative expression, the stannous
salt concentration ranges from about 15 grams per liter to about 150 grams per liter,
based on the total volume of the electrolyte solution 554. In another alternative
expression, the stannous salt concentration ranges from about 15 grams per liter to
about 100 grams per liter, based on the total volume of the electrolyte solution 554.
In another alternative expression, the stannous salt concentration ranges from about
20 grams per liter to about 100 grams per liter, based on the total volume of the
electrolyte solution 554. In another alternative expression, the stannous salt concentration
ranges from about 20 grams per liter to about 50 grams per liter, based on the total
volume of the electrolyte solution 554. In yet alternative expression, the stannous
salt concentration ranges from about 25 grams per liter to about 35 grams per liter,
based on the total volume of the electrolyte solution 554.
[0075] The bismuth salt in the electrolyte solution 554 provides bismuth (Bi
3+) ions. In one formulation, the bismuth salt in the electrolyte solution 554 is bismuth
sulfate (Bi
2(SO
4)
3). In another formulation, the bismuth salt in the electrolyte solution 554 is bismuth
oxide (Bi
2O
3). In another formulation, the bismuth salt in the electrolyte solution 554 is bismuth
nitrate (Bi(NO
3)
3). In another formulation, the bismuth salt in the electrolyte solution 554 is bismuth
chloride (BiCl
3). In another formulation, the bismuth salt in the electrolyte solution 554 is bismuth
trifluoride (BiF
3). In yet another formulation, the bismuth salt in the electrolyte solution 554 includes
at least two of bismuth sulfate (Bi
2(SO
4)
3), bismuth oxide (Bi
2O
3), bismuth nitrate (Bi(NO
3)
3), bismuth chloride (BiCl
3), and bismuth trifluoride (BiF
3).
[0076] The bismuth salt in the electrolyte solution 554 may be present at a concentration
ranging from about 0.25 grams per liter to about 10 grams per liter, based on the
total volume of the electrolyte solution 554. In one alternative expression, the bismuth
salt concentration ranges from about 0.25 grams per liter to about 5 grams per liter,
based on the total volume of the electrolyte solution 554. In another alternative
expression, the bismuth salt concentration ranges from about 0.25 grams per liter
to about 2.5 grams per liter, based on the total volume of the electrolyte solution
554. In another alternative expression, the bismuth salt concentration ranges from
about 0.25 grams per liter to about 1 grams per liter, based on the total volume of
the electrolyte solution 554. In another alternative expression, the bismuth salt
concentration ranges from about 0.3 grams per liter to about 0.8 grams per liter,
based on the total volume of the electrolyte solution 554. In another alternative
expression, the bismuth salt concentration ranges from about 0.4 grams per liter to
about 4 grams per liter, based on the total volume of the electrolyte solution 554.
In yet alternative expression, the bismuth salt concentration ranges from about 0.4
grams per liter to about 0.7 grams per liter, based on the total volume of the electrolyte
solution 554.
[0077] The acid reduces the pH of the electrolyte solution 554. In one formulation, the
acid in the electrolyte solution 554 is sulfuric acid (H
2SO
4). In another formulation, the acid in the electrolyte solution 554 is sulfamic acid
(H
3NSO
3). In yet another formulation, the acid in the electrolyte solution 554 includes both
sulfuric acid (H
2SO
4) and sulfamic acid (H
3NSO
3).
[0078] The acid in the electrolyte solution 554 may be present at a concentration ranging
from about 50 milliliters per liter to about 150 milliliters per liter, based on the
total volume of the electrolyte solution 554. In one alternative expression, the acid
concentration ranges from about 60 milliliters per liter to about 140 milliliters
per liter, based on the total volume of the electrolyte solution 554. In another alternative
expression, the acid concentration ranges from about 70 milliliters per liter to about
130 milliliters per liter, based on the total volume of the electrolyte solution 554.
In another alternative expression, the acid concentration ranges from about 75 milliliters
per liter to about 125 milliliters per liter, based on the total volume of the electrolyte
solution 554. In another alternative expression, the acid concentration ranges from
about 80 milliliters per liter to about 120 milliliters per liter, based on the total
volume of the electrolyte solution 554. In yet another alternative expression, the
acid concentration ranges from about 90 milliliters per liter to about 110 milliliters
per liter, based on the total volume of the electrolyte solution 554.
[0079] Additional components may be included in the electrolyte solution 554 without departing
from the scope of the present disclosure. Various carriers and/or additives may be
included in the electrolyte solution 554. As one specific, non-limiting example, the
electrolyte solution 554 may include TIN MAC HT STARTER A, a proprietary surfactant,
which is commercially available from MacDermid of Waterbury, Connecticut. As another
specific, non-limiting example, the electrolyte solution 554 may include TIN MAC HT
STARTER B, a proprietary source of methacrylic acid, which is commercially available
from MacDermid of Waterbury, Connecticut. As yet another specific, non-limiting example,
the electrolyte solution 554 may include TIN MAC HT REPLENISHER, a proprietary source
of dipropylene glycol methyl ether and surfactant, which is commercially available
from MacDermid of Waterbury, Connecticut
[0080] As one specific, non-limiting example, the electrolyte solution 554 includes water,
30 grams per liter stannous sulfate (SnSO
4), 0.58 grams per liter bismuth sulfate (Bi
2(SO
4)
3), 105 milliliters per liter sulfuric acid (H
2SO
4), 20 milliliters per liter TIN MAC HT STARTER A, 5 milliliters per liter TIN MAC
HT STARTER B, and 3 milliliters per liter TIN MAC HT REPLENISHER.
[0081] The electrolyte solution 554 may be manufactured in various ways without departing
from the scope of the present disclosure. In one particular implementation, the disclosed
method for manufacturing the electrolyte solution 554 includes steps of (1) mixing
the acid (e.g., 66 degree Baume sulfuric acid) with water (e.g., deionized water)
to yield an acidic solution, (2) dissolving the stannous salt (e.g., stannous sulfate
(SnSO
4)) in the acidic solution, (3) dissolving the bismuth salt (e.g., bismuth sulfate
(Bi
2(SO
4)
3)) in the solution, (4) optionally adding one or more additives/carriers (e.g., TIN
MAC HT STARTER A, TIN MAC HT STARTER B and/or TIN MAC HT REPLENISHER), and (5) adding
additional water, if needed, to make up the required total volume of the electrolyte
solution 554.
[0082] At Block 504 (Fig. 10), the substrate 556 is immersed (e.g., completely immersed)
in the electrolyte solution 554. A lead 566 may electrically couple the immersed substrate
556 with a first terminal 562 of the current source 560.
[0083] At Block 506 (Fig. 10), the anode 558 is immersed (e.g., completely immersed) in
the electrolyte solution 554. A lead 568 may electrically couple the immersed anode
558 with a second terminal 564 of the current source 560.
[0084] At Block 508 (Fig. 10), the current source 560 is actuated such that an electric
current is passed between the substrate 556 and the anode 558. The electric current
will cause a tin-bismuth alloy to deposit onto the substrate 556.
[0085] The step of passing an electric current (Block 508) may be performed at various current
densities without departing from the scope of the present disclosure. Those skilled
in the art will appreciate that current density is a controllable parameter, and selection
of an appropriate current density may require consideration of various factors, such
as the duration of the passing step (Block 508), among other factors. In one expression,
the electric current passed during the passing step (Block 508) may have a current
density ranging from about 10 amperes per square foot to about 80 amperes per square
foot, based on the surface area of the substrate 556. In another expression, the electric
current passed during the passing step (Block 508) may have a current density ranging
from about 10 amperes per square foot to about 50 amperes per square foot, based on
the surface area of the substrate 556. In another expression, the electric current
passed during the passing step (Block 508) may have a current density ranging from
about 20 amperes per square foot to about 40 amperes per square foot, based on the
surface area of the substrate 556. In another expression, the electric current passed
during the passing step (Block 508) may have a current density ranging from about
15 amperes per square foot to about 30 amperes per square foot, based on the surface
area of the substrate 556. In yet another expression, the electric current passed
during the passing step (Block 508) may have a current density of about 30 amperes
per square foot, based on the surface area of the substrate 556.
[0086] The step of passing an electric current (Block 508) may be performed for various
durations of time without departing from the scope of the present disclosure. Those
skilled in the art will appreciate that the current duration is a controllable parameter,
and selection of an appropriate duration of time may require consideration of various
factors, such as the current density, among other factors. In one expression, the
passing step (Block 508) may be performed for about 5 minutes to about 120 minutes.
In another expression, the passing step (Block 508) may be performed for about 5 minutes
to about 60 minutes. In another expression, the passing step (Block 508) may be performed
for about 10 minutes to about 30 minutes. In another expression, the passing step
(Block 508) may be performed for about 10 minutes to about 20 minutes. In yet another
expression, the passing step (Block 508) may be performed for about 15 minutes.
[0087] At Block 510 (Fig. 10), the substrate 556 is disconnected from the current source
560 and removed from the electrolyte solution 554.
[0088] At Block 512 (Fig. 10), the substrate 556 may be rinsed with a rinsing fluid. As
an example, the rinsing fluid may be water, such as deionized water.
[0089] Examples of the disclosure may be described in the context of an aircraft manufacturing
and service method 1000, as shown in Fig. 12, and an aircraft 1002, as shown in Fig.
13. During pre-production, the aircraft manufacturing and service method 1000 may
include specification and design 1004 of the aircraft 1002 and material procurement
1006. During production, component/subassembly manufacturing 1008 and system integration
1010 of the aircraft 1002 takes place. Thereafter, the aircraft 1002 may go through
certification and delivery 1012 in order to be placed in service 1014. While in service
by a customer, the aircraft 1002 is scheduled for routine maintenance and service
1016, which may also include modification, reconfiguration, refurbishment and the
like.
[0090] Each of the processes of method 1000 may be performed or carried out by a system
integrator, a third party, and/or an operator (e.g., a customer). For the purposes
of this description, a system integrator may include without limitation any number
of aircraft manufacturers and major-system subcontractors; a third party may include
without limitation any number of venders, subcontractors, and suppliers; and an operator
may be an airline, leasing company, military entity, service organization, and so
on.
[0091] As shown in Fig. 13, the aircraft 1002 produced by example method 1000 may include
an airframe 1018 with a plurality of systems 1020 and an interior 1022. Examples of
the plurality of systems 1020 may include one or more of a propulsion system 1024,
an electrical system 1026, a hydraulic system 1028, and an environmental system 1030.
Any number of other systems may be included.
[0092] The disclosed compositions and methods may be used during any one or more of the
stages of the aircraft manufacturing and service method 1000. As one example, components
or subassemblies corresponding to component/subassembly manufacturing 1008, system
integration 1010, and or maintenance and service 1016 may be fabricated or manufactured
using the disclosed compositions and methods. As another example, the airframe 1018
may be constructed using the disclosed compositions and methods. Also, one or more
apparatus examples, method examples, or a combination thereof may be utilized during
component/subassembly manufacturing 1008 and/or system integration 1010, for example,
by substantially expediting assembly of or reducing the cost of an aircraft 1002,
such as the airframe 1018 and/or the interior 1022. Similarly, one or more of system
examples, method examples, or a combination thereof may be utilized while the aircraft
1002 is in service, for example and without limitation, to maintenance and service
1016.
[0093] The disclosure further comprises the following illustrative, non-exhaustive enumerative
examples, which may or may not be claimed.
Example 1. An activation solution comprising: water; an ammonium salt comprising a
fluorine-containing anion; and sulfuric acid.
Example 2. The activation solution of Example 1 wherein the ammonium salt comprises
at least one of ammonium bifluoride and ammonium tetrafluoroborate.
Example 3. The activation solution of Example 1 or Example 2 wherein the ammonium
salt is ammonium bifluoride.
Example 4. The activation solution of any of Examples 1 to 3 wherein the ammonium
salt is ammonium tetrafluoroborate.
Example 5. The activation solution of any of Examples 1 to 4 wherein the ammonium
salt is present at a concentration ranging from about 10 grams per liter to about
150 grams per liter, based on a total volume of the activation solution.
Example 6. The activation solution of any of Examples 1 to 5 wherein the ammonium
salt is present at a concentration ranging from about 20 grams per liter to about
120 grams per liter, based on a total volume of the activation solution.
Example 7. The activation solution of any of Examples 1 to 6 wherein the ammonium
salt is present at a concentration ranging from about 40 grams per liter to about
100 grams per liter, based on a total volume of the activation solution.
Example 8. The activation solution of any of Examples 1 to 7 wherein the ammonium
salt is present at a concentration of about 80 grams per liter, based on a total volume
of the activation solution.
Example 9. The activation solution of any of Examples 1 to 8 wherein the sulfuric
acid is present at a concentration ranging from about 1 percent by volume to about
70 percent by volume, based on a total volume of the activation solution.
Example 10. The activation solution of any of Examples 1 to 9 wherein the sulfuric
acid is present at a concentration ranging from about 2 percent by volume to about
50 percent by volume, based on a total volume of the activation solution.
Example 11. The activation solution of any of Examples 1 to 10 wherein the sulfuric
acid is present at a concentration ranging from about 5 percent by volume to about
25 percent by volume, based on a total volume of the activation solution.
Example 12. The activation solution of any of Examples 1 to 11 wherein the sulfuric
acid is present at a concentration of about 10 percent by volume, based on a total
volume of the activation solution.
Example 13. The activation solution of any of Examples 1 to 12 maintained at atmospheric
pressure and a temperature ranging from about 15 °C to about 50 °C.
Example 14. A method for manufacturing the activation solution of any of Examples
1 to 13, the method comprising: mixing the sulfuric acid with at least a portion of
the water to yield an acidic solution; and dissolving the ammonium salt in the acidic
solution.
Example 15. A method for pretreating a substrate prior to depositing a material thereon,
the method comprising: immersing the substrate in the activation solution of Claim
1 for a predetermined period of time.
Example 16. The method of Example 15 wherein the substrate is a titanium substrate,
and wherein the predetermined period of time is a time between about 5 seconds and
about 120 seconds.
Example 17. The method of Example 15 or Example 16 wherein the substrate is a titanium
substrate, and wherein the predetermined period of time is a time between about 20
seconds and about 40 seconds.
Example 18. The method of any of Examples 15 to 17 further comprising: removing the
substrate from the activation solution after the predetermined period of time has
elapsed; and after the removing, rinsing the substrate with a rinsing fluid.
Example 19. The method of any of Examples 15 to 18 wherein the rinsing fluid is deionized
water.
Example 20. The method of any of Examples 15 to 19 further comprising: after the immersing,
subjecting the substrate to an anodic sulfuric acid method.
[0094] The disclosed compositions and methods are described in the context of an aircraft;
however, one of ordinary skill in the art will readily recognize that the disclosed
compositions and methods may be utilized for a variety of applications. For example,
the disclosed compositions and methods may be implemented in various types of vehicles
including, for example, helicopters, passenger ships, automobiles, marine products
(boat, motors, etc.) and the like.
[0095] Although various expressions of the disclosed compositions and methods for activating
metallic substrates have been illustrated and described, modifications may occur to
those skilled in the art upon reading the specification. The present application includes
such modifications and is limited only by the scope of the claims.