Compositions and methods for activating titanium substrates

Abstract

To provide a composition, a system, and a method for activating a metal substrate (for example, a metallic fastener or other components / elements).SOLUTION: A method, for pretreating a substrate prior to stacking materials on the substrate, includes immersing the substrate in an activation solution for a predetermined period of time. The activation solution includes ammonium salt containing a fluorine-containing anion, sulfuric acid, and water.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This application relates to depositing materials onto substrates, and more particularly to compositions and methods for activating metal substrates and for electrodepositing tin-bismuth alloys onto metal substrates.

[0002] Mechanical fasteners are widely used to join two or more components for structural assemblies. For example, mechanical fasteners are widely used to join structural components in aircraft fuselages.

[0003] Aircraft are subject to electromagnetic effects (EME) from a variety of sources (e.g., lightning strikes and precipitation static). Metallic aircraft structures are directly conductive and therefore relatively insensitive to EME. However, composite (e.g., carbon fiber reinforced plastic) aircraft structures do not readily dissipate the significant electrical currents and electromagnetic forces resulting from EME. Therefore, when mechanical fasteners are used in composite aircraft structures, measures must be taken to protect them from EME.

[0004] Protection from electromagnetic effects can be provided to mechanical fasteners in the form of conductive metallic surface deposits (e.g., metal plating). While various metallic surface deposits can provide adequate conductivity to impart protection from electromagnetic effects, other factors (e.g., lubricity and galvanic compatibility with carbon fiber reinforced plastics) are also considered for mechanical fasteners intended for the aerospace industry.

[0005] Tin exists in α and β phases. Alpha-tin is gray in color and forms a paste in powder form, while beta-tin is white and has a tetragonal crystal structure. When tin is alloyed with bismuth at concentrations greater than 0.4 weight percent bismuth, the tin begins to exist as the β phase. Tin-bismuth has shown promise as a metal surface deposit suitable 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 to conduct research and development efforts in the field of electrodeposition.

[0007] Implementations include the following:

[0008] An activation solution containing water, an ammonium salt having a fluorine-containing anion, and sulfuric acid.

[0009] An activation solution containing water, ammonium bifluoride and / or ammonium tetrafluoroborate dissolved in water, and sulfuric acid dissolved in water.

[0010] 1. An activation solution comprising water, ammonium bifluoride and / or ammonium tetrafluoroborate dissolved in water at a concentration of about 10 grams per liter to about 150 grams per liter based on the total volume of the activation solution, and sulfuric acid dissolved in water at a concentration ranging from about 1 volume percent to about 70 volume percent based on the total volume of the activation solution.

[0011] 1. An activation solution comprising water, ammonium bifluoride dissolved in water at a concentration of about 20 grams per liter to about 120 grams per liter based on the total volume of the activation solution, and sulfuric acid dissolved in water at a concentration of about 5 percent to about 25 percent by volume based on the total volume of the activation solution.

[0012] 1. A method for preparing an activation solution, comprising: (1) mixing sulfuric acid and water to obtain an acidic solution; and (2) dissolving an ammonium salt having a fluorine-containing anion in an acidic solution; A method comprising:

[0013] 1. A method for pretreating a substrate prior to depositing a material thereon, the method comprising immersing the substrate in an activating solution for a predetermined period of time, the activating solution comprising water, an ammonium salt having a fluorine-containing anion dissolved in the water, and sulfuric acid dissolved in the water.

[0014] Other aspects of the disclosed compositions and methods for activating metal substrates will become apparent from the following detailed description, the accompanying drawings, and the appended claims. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a flow diagram illustrating a method according to the present disclosure for depositing a material onto a substrate. [Figure 2] 2 is a photomicrograph of a tin-bismuth alloy deposited on a titanium substrate according to the method of FIG. 1. [Figure 3] 2 is a flow diagram illustrating one method according to the present disclosure for activating a substrate (eg, a titanium substrate) according to the method of FIG. 1. [Figure 4] 4 shows a schematic diagram of a system for activating a substrate according to the method of FIG. [Figure 5] 2 is a flow diagram illustrating another method according to the present disclosure for activating a substrate (eg, a titanium substrate) in accordance with the method of FIG. 1. [Figure 6] 6 shows a schematic diagram of a system for activating a substrate according to the method of FIG. 5. [Figure 7] 2 is a flow diagram illustrating yet another method according to the present disclosure for activating a substrate (eg, a titanium substrate) in accordance with the method of FIG. 1. [Figure 8] 8 illustrates a schematic diagram of a system for activating a substrate according to the method of FIG. 7. [Figure 9] 2 shows a schematic diagram of a system for strike plating a substrate in accordance with the method of FIG. 1. [Figure 10] 2 is a flow diagram illustrating one method according to the present disclosure for electrodepositing a tin-bismuth alloy onto a substrate according to the method of FIG. 1. [Figure 11] 11 shows a schematic of an electrodeposition system for depositing a tin-bismuth alloy according to the method of FIG. [Figure 12] 1 is a flow diagram of an aircraft manufacturing and operations methodology. [Figure 13] 1 is a block diagram of an aircraft.

[0016] Disclosed herein are compositions, systems, and methods for activating metal substrates (e.g., metal fasteners or other members / components). Also disclosed are compositions, systems, and methods for depositing materials onto metal substrates (e.g., metal fasteners or other members / components). The compositions, systems, and methods disclosed herein can be used separately or in various combinations to achieve a desired material deposition on a substrate.

[0017] 1, a method for depositing material onto a substrate is disclosed, generally designated 10. Although only three general steps are shown, one skilled in the art will understand that various additional steps may occur before, after, or between the steps presented herein without departing from the scope of the present disclosure.

[0018] The first step (block 12) of method 10 involves pretreating the substrate to make it suitable for receiving a material thereon (e.g., a metal deposit or other metallic or non-metallic material). Various pretreatments (e.g., cleaning, degreasing, etching, etc.) can be performed. In particular, the pretreatment step (block 12) can include activating the substrate surface (block 14). For example, in the case of a titanium substrate, activating the substrate surface (block 14) can remove (or at least substantially reduce) the tough oxide layer known to form on the substrate.

[0019] An intermediate step (block 16) of method 10 involves strike plating the pretreated substrate. Strike plating the substrate surface (block 16) can form a thin metal layer on the substrate surface, providing the substrate with a surface that is better suited to receiving and bonding with subsequent metal deposits. In certain implementations, the strike plating step (block 16) can form a thin nickel layer on the substrate surface.

[0020] The final step (block 18) of method 10 involves electrodeposition onto the strike-plated substrate. The electrodeposition step (block 18) can form a metal deposit on the substrate surface. In a particular implementation, the electrodeposition step (block 18) can deposit a tin-bismuth alloy onto the substrate surface.

[0021] 2, the disclosed method 10 was used to deposit a thin layer of tin-bismuth alloy onto the surface of a titanium alloy (Ti-6Al-4V) substrate, resulting in excellent bonding between the tin-bismuth alloy deposit and the underlying titanium alloy substrate.

[0022] While this disclosure focuses primarily on titanium substrates (substrates formed from titanium or titanium alloys, e.g., Ti-6Al-4V), the disclosed method 10, as well as each step of the disclosed method 10 (e.g., the activation step (block 14), the strike plating step (block 16), and / or the electrodeposition step (block 18)), may also be suitable for non-titanium substrates. Examples of non-titanium substrates that may benefit from the present disclosure include, but are not limited to, iron alloys, copper alloys, and nickel alloys (e.g., Inconel).

[0023] activation Three activation methods are disclosed, including related compositions and systems. A metal substrate, such as a titanium substrate, can be activated using only one of the disclosed activation methods. Alternatively, a metal substrate, such as a titanium substrate, can be activated using multiple activation methods (e.g., a series of activation methods), including one or more of the disclosed activation methods.

[0024] 3 and 4, a first activation method (generally designated 100) may begin at block 110 (FIG. 3) and includes preparing a bath 152 containing an activation solution 154, as shown in FIG. 4. The bath 152 and activation solution 154 may comprise a first activation system 150.

[0025] The bath 152 can be any container suitable for receiving and containing the activation solution 154. Compositionally, the materials forming the bath 152 must be chemically compatible with the activation solution 154. Of course, the bath 152 must be sized and shaped to receive therein the substrate 156 to be activated by the first activation system 150.

[0026] The activation solution 154 contains water (H2O), an ammonium salt dissolved in water, and sulfuric acid (H2SO4) dissolved in water. The activation solution 154 can 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 (about 21°C)). However, higher and lower pressures, as well as higher and lower temperatures, are contemplated without departing from the scope of the present disclosure.

[0027] The ammonium salt in activating solution 154 can have a fluorine-containing anion. In one formulation, the ammonium salt in activating solution 154 is ammonium bifluoride (NHHF). In another formulation, the ammonium salt in activating solution 154 is ammonium tetrafluoroborate (NHBF). In yet another formulation, the ammonium salt in activating solution 154 includes both ammonium bifluoride (NHHF) and ammonium tetrafluoroborate (NHBF).

[0028] The ammonium salt in the activating 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 activating solution 154. Expressed alternatively, the concentration of the ammonium salt ranges from about 20 grams per liter to about 120 grams per liter, based on the total volume of the activating solution 154. Expressed alternatively, the concentration of the ammonium salt ranges from about 30 grams per liter to about 110 grams per liter, based on the total volume of the activating solution 154. Expressed alternatively, the concentration of the ammonium salt ranges from about 40 grams per liter to about 100 grams per liter, based on the total volume of the activating solution 154. Expressed alternatively, the concentration of the ammonium salt ranges from about 50 grams per liter to about 100 grams per liter, based on the total volume of the activating solution 154. Expressed alternatively, the concentration of the ammonium salt is in the range of about 60 grams per liter to about 100 grams per liter, based on the total volume of the activation solution 154. Expressed alternatively, the concentration of the ammonium salt is in the range of about 70 grams per liter to about 90 grams per liter, based on the total volume of the activation solution 154. Expressed further alternatively, the concentration of the ammonium salt is about 80 grams per liter, based on the total volume of the activation solution 154.

[0029] The sulfuric acid in the activation solution 154 may be present at a concentration ranging from about 1 volume percent to about 70 volume percent, based on the total volume of the activation solution 154. Expressed alternatively, the sulfuric acid concentration ranges from about 2 volume percent to about 50 volume percent, based on the total volume of the activation solution 154. Expressed alternatively, the sulfuric acid concentration ranges from about 3 volume percent to about 40 volume percent, based on the total volume of the activation solution 154. Expressed alternatively, the sulfuric acid concentration ranges from about 4 volume percent to about 30 volume percent, based on the total volume of the activation solution 154. Expressed alternatively, the sulfuric acid concentration ranges from about 5 volume percent to about 25 volume percent, based on the total volume of the activation solution 154. Expressed alternatively, the sulfuric acid concentration ranges from about 5 volume percent to about 15 volume percent, based on the total volume of the activation solution 154. Expressed further alternatively, the sulfuric acid concentration is about 10 volume percent, based on the total volume of the activation solution 154.

[0030] In one specific, non-limiting example, the activation solution 154 includes water, 80 grams per liter of ammonium bifluoride (NH4HF2), and 10 volume percent sulfuric acid (H2SO4).

[0031] Activation solution 154 can be prepared in a variety of ways without departing from the scope of the present disclosure. In one specific implementation, the disclosed method for preparing activation solution 154 includes the following steps: (1) mixing sulfuric acid (e.g., 66° Baume sulfuric acid) with at least a portion of water (e.g., deionized water) to obtain an acidic solution; (2) dissolving an ammonium salt (e.g., ammonium bifluoride and / or ammonium tetrafluoroborate) in an acidic solution; and (3) Adding more water, if necessary, to bring the activation solution 154 to the required total volume.

[0032] In block 120 (FIG. 3), the substrate 156 is immersed (e.g., fully submerged) in the activation solution 154. The substrate 156 may remain immersed in the activation solution 154 for a predetermined time, as shown in block 130 (FIG. 3), before removing the substrate 156 from the activation solution 154. For a titanium substrate (substrate 156), the predetermined time may be selected to allow the activation solution 154 to reduce / eliminate any stubborn oxide layer on the substrate 156 without significantly damaging the underlying oxide layer of the titanium / titanium alloy. In one expression, the predetermined time is between about 5 seconds and about 120 seconds. In another expression, the predetermined time is between about 10 seconds and about 100 seconds. In another expression, the predetermined time is between about 20 seconds and about 40 seconds. In yet another expression, the predetermined time is about 30 seconds.

[0033] In block 140 (FIG. 3), the substrate 156 may be rinsed with a rinsing fluid after being removed from the activation solution 154. As one example, the rinsing fluid may be water, such as deionized water.

[0034] 5 and 6, a second activation method (generally designated 200) may begin at block 202 (FIG. 5) and includes preparing a bath 252 containing an activation solution 254, as shown in FIG. 6. The bath 252 and activation solution 254 may comprise a second activation system 250.

[0035] Bath 252 can be any container suitable for receiving and containing activation solution 254. Compositionally, the materials forming bath 252 must be chemically compatible with activation solution 254. Of course, bath 252 must be sized and shaped to receive therein substrate 256 to be activated by second activation system 250.

[0036] The activation solution 254 contains water (H2O), a fluoride salt dissolved in water, hydrofluoric acid (HF) dissolved in water, and sulfuric acid (H2SO4) dissolved in water. The activation solution 254 can 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 (about 21°C)). However, higher and lower pressures, as well as higher and lower temperatures, are contemplated without departing from the scope of the present disclosure.

[0037] The fluoride salt in the activation solution 254 can 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). In another formulation, the ammonium salt in the activation solution 254 is strontium fluoride (SrF). In yet another formulation, the fluoride salts in activation solution 254 include at least two of potassium fluoride (KF), lithium fluoride (LiF), sodium fluoride (NaF), rubidium fluoride (RuF), barium fluoride (BaF), and strontium fluoride (SrF).

[0038] 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed further alternatively, the concentration of the fluoride salt is about 20 grams per liter, based on the total volume of the activation solution 254.

[0039] 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. Expressed alternatively, the concentration of the hydrofluoric acid ranges from about 10 milliliters per liter to about 200 milliliters per liter, based on the total volume of the activation solution 254. Expressed alternatively, the concentration of the hydrofluoric acid ranges from about 15 milliliters per liter to about 150 milliliters per liter, based on the total volume of the activation solution 254. Expressed alternatively, the concentration of the hydrofluoric acid ranges from about 20 milliliters per liter to about 150 milliliters per liter, based on the total volume of the activation solution 254. Expressed alternatively, the concentration of the hydrofluoric acid ranges from about 30 milliliters per liter to about 100 milliliters per liter, based on the total volume of the activation solution 254. Expressed alternatively, the concentration of hydrofluoric acid ranges from about 40 milliliters per liter to about 80 milliliters per liter, based on the total volume of activation solution 254. Expressed further alternatively, the concentration of hydrofluoric acid is about 60 milliliters per liter, based on the total volume of activation solution 254.

[0040] The sulfuric acid in the activation solution 254 may be present at a concentration ranging from about 1 volume percent to about 45 volume percent, based on the total volume of the activation solution 254. Expressed alternatively, the sulfuric acid concentration ranges from about 2 volume percent to about 35 volume percent, based on the total volume of the activation solution 254. Expressed alternatively, the sulfuric acid concentration ranges from about 2 volume percent to about 20 volume percent, based on the total volume of the activation solution 254. Expressed alternatively, the sulfuric acid concentration ranges from about 3 volume percent to about 15 volume percent, based on the total volume of the activation solution 254. Expressed alternatively, the sulfuric acid concentration ranges from about 3 volume percent to about 10 volume percent, based on the total volume of the activation solution 254. Expressed further alternatively, the sulfuric acid concentration is about 5 volume percent, based on the total volume of the activation solution 254.

[0041] In one specific, non-limiting example, the activation solution 254 includes water, 20 grams per liter of potassium fluoride (KF), 60 milliliters per liter of hydrofluoric acid (HF), and 5 volume percent sulfuric acid (H2SO4).

[0042] Activation solution 254 can be prepared in a variety of ways without departing from the scope of the present disclosure. In one specific implementation, the disclosed method for preparing activation solution 254 includes the following steps: (1) mixing sulfuric acid (e.g., 66° Baume sulfuric acid) and water (e.g., deionized water) to obtain a first acidic solution; (2) mixing hydrofluoric acid (e.g., 48% by weight in water) with the first acidic solution to obtain a second acidic solution; (3) dissolving a fluoride salt (e.g., potassium fluoride) in the second acidic solution; and (4) Adding more water, if necessary, to bring activation solution 254 to the required total volume.

[0043] In block 204 (FIG. 5), the substrate 256 is immersed (e.g., fully submerged) in the activation solution 254. The substrate 256 may remain immersed in the activation solution 254 for a predetermined time, as shown in block 206 (FIG. 5), before removing the substrate 256 from the activation solution 254. For a titanium substrate (substrate 256), the predetermined time may be selected to allow the activation solution 254 to reduce / eliminate any stubborn oxide layer on the substrate 256 without significantly damaging the underlying oxide layer of the titanium / titanium alloy. In one expression, the predetermined time is between about 5 seconds and about 120 seconds. In another expression, the predetermined time is between about 10 seconds and about 100 seconds. In another expression, the predetermined time is between about 20 seconds and about 40 seconds. In yet another expression, the predetermined time is about 30 seconds.

[0044] In block 208 (FIG. 5), the substrate 256 may be rinsed with a rinsing fluid after being removed from the activation solution 254. As one example, the rinsing fluid may be water, such as deionized water.

[0045] 7 and 8, the third activation method (generally designated 300) may begin at block 302 (FIG. 7) and includes preparing a bath 352 containing an activation solution 354, as shown in FIG. 8. The bath 352 and activation solution 354, along with a graphite electrode 358 and a current source 360, may comprise a third activation system 350, which may be used to perform the anodic sulfuric acid process (third activation method 300) as described herein.

[0046] Bath 352 can be any container suitable for receiving and containing activation solution 354. Compositionally, the materials forming bath 352 must be chemically compatible with activation solution 354. Of course, bath 352 must be sized and shaped to accommodate therein graphite electrode 358 and substrate 356 to be activated by third activation system 350.

[0047] The activation solution 354 includes water (H2O) and sulfuric acid (H2SO4) dissolved in water. The activation solution 354 can 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 (about 21°C)). However, higher and lower pressures, as well as higher and lower temperatures, are contemplated without departing from the scope of the present disclosure.

[0048] The sulfuric acid in the activation solution 354 can be present at a concentration ranging from about 5 volume percent to about 45 volume percent, based on the total volume of the activation solution 354. Expressed alternatively, the sulfuric acid concentration ranges from about 5 volume percent to about 35 volume percent, based on the total volume of the activation solution 354. Expressed alternatively, the sulfuric acid concentration ranges from about 5 volume percent to about 30 volume percent, based on the total volume of the activation solution 354. Expressed alternatively, the sulfuric acid concentration ranges from about 5 volume percent to about 25 volume percent, based on the total volume of the activation solution 354. Expressed alternatively, the sulfuric acid concentration ranges from about 10 volume percent to about 20 volume percent, based on the total volume of the activation solution 354. Expressed further alternatively, the sulfuric acid concentration is about 15 volume percent, based on the total volume of the activation solution 354.

[0049] In one specific, non-limiting example, the activation solution 354 includes water and 15 volume percent sulfuric acid (H2SO4).

[0050] In block 304 (FIG. 7), a substrate 356 is immersed (e.g., completely submerged) in an activation solution 354. A conductive wire 368 can electrically connect the immersed substrate 356 to a first terminal 364 of a current source 360.

[0051] In block 306 (FIG. 7), the graphite electrode 358 is immersed (e.g., completely submerged) in the activation solution 354. A wire 366 can electrically connect the immersed graphite electrode 358 to a second terminal 362 of a current source 360.

[0052] In block 308 (FIG. 7), a current source 360 ​​is activated such that a current passes between the substrate 356 and the graphite electrode 358. The current source 360 ​​may be configured such that the substrate 356 acts as an anode, thereby etching the substrate 356. In the case of a titanium substrate (substrate 356), the anodic sulfuric acid method (third activation method 300) can reduce / eliminate the strong oxide layer on the substrate 356 without significantly damaging the underlying oxide layer of the titanium / titanium alloy.

[0053] The current passing step (block 308) can 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 that selecting an appropriate current density requires consideration of various factors, such as the duration of the current passing step (block 308), among other factors. Expressed in one manner, the current passed during the current passing step (block 308) can have a current density ranging from about 10 amps per square foot to about 80 amps per square foot, based on the surface area of ​​the substrate 356. Expressed in another manner, the current passed during the current passing step (block 308) can have a current density ranging from about 20 amps per square foot to about 60 amps per square foot, based on the surface area of ​​the substrate 356. Alternatively expressed, the current passed during the passing of current step (block 308) can have a current density ranging from about 20 amps per square foot to about 40 amps per square foot, based on the surface area of ​​substrate 356. Alternatively expressed still, the current passed during the passing of current step (block 308) can have a current density of about 30 amps per square foot, based on the surface area of ​​substrate 356.

[0054] The current passing step (block 308) can be performed for various durations without departing from the scope of the present disclosure. Those skilled in the art will appreciate that current density is a controllable parameter and that selecting an appropriate duration requires consideration of various factors (e.g., current density, among other factors). In one expression, the current passing step (block 308) can be performed for about 5 seconds to about 120 seconds. In another expression, the current passing step (block 308) can be performed for about 10 seconds to about 100 seconds. In another expression, the current passing step (block 308) can be performed for about 10 seconds to about 60 seconds. In another expression, the current passing step (block 308) can be performed for about 15 seconds to about 45 seconds. In yet another expression, the current passing step (block 308) can be performed for about 20 seconds to about 30 seconds.

[0055] In block 310 (FIG. 7), the substrate 356 is disconnected from the current source 360 ​​and removed from the activation solution 354.

[0056] In block 312 (FIG. 7), the substrate 356 may be rinsed with a rinsing fluid. As one example, the rinsing fluid may be water, such as deionized water.

[0057] Strike plating Various strike plating processes (including nickel strike plating processes, e.g., Wood's bath nickel strike) are known in the art and can be used in the method 10 of Figure 1 without departing from the scope of the present disclosure. However, a specific nickel strike plating method has been disclosed that resulted in excellent bonding to the substrate upon subsequent plating (see Figure 2).

[0058] 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 a current source 460. The current source 460 may include a first terminal 462 and a second terminal 464. The nickel anode 458 may be electrically connected to the second terminal 464 by a conductor 468.

[0059] Bath 452 can be any container suitable for receiving and containing electrolyte solution 454. Compositionally, the materials forming bath 452 must be chemically compatible with electrolyte solution 454. Of course, bath 452 must be sized and shaped to receive substrate 456 and nickel anode 458 therein.

[0060] The electrolyte solution 454 contains water (H2O), nickel chloride (NiCl2) dissolved in water, and hydrochloric acid (HCl) dissolved in water. The electrolyte solution 454 can 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 (about 21°C)). However, higher and lower pressures, as well as higher and lower temperatures, are contemplated without departing from the scope of the present disclosure.

[0061] 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, the concentration of nickel chloride ranges from about 175 grams per liter to about 225 grams per liter, based on the total volume of activation solution 354.

[0062] 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. Expressed alternatively, the concentration of the hydrochloric acid ranges from about 50 milliliters per liter to about 250 milliliters per liter, based on the total volume of the electrolyte solution 454. Expressed alternatively, the concentration of the hydrochloric acid ranges from about 75 milliliters per liter to about 225 milliliters per liter, based on the total volume of the electrolyte solution 454. Expressed alternatively, the concentration of the hydrochloric acid ranges from about 100 milliliters per liter to about 200 milliliters per liter, based on the total volume of the electrolyte solution 454. Expressed alternatively, the concentration of the hydrochloric acid ranges from about 125 milliliters per liter to about 175 milliliters per liter, based on the total volume of the electrolyte solution 454.

[0063] In one specific, non-limiting example, the electrolyte solution 454 includes water, 200 grams per liter of nickel chloride (NiCl 2 ), and 150 milliliters per liter of hydrochloric acid (HCl).

[0064] 9, a substrate 456 is immersed (e.g., completely submerged) in an electrolyte solution 454 in a bath 452. The substrate 456 is electrically connected to a first terminal 462 of a current source 460 by a conductor 466.

[0065] To begin strike plating, a current source 460 is activated such that a current passes between the substrate 456 and the nickel anode 458, forming a deposit on the substrate 456. Optionally, an anodic strike (substrate 456 acts as the anode) can be performed to etch the substrate 456 before the cathodic strike begins.

[0066] The anode strike (etching) can be performed at various current densities and durations without departing from the scope of the present disclosure. In one expression, the anode strike can be performed at a current density ranging from about 25 amps per square foot to about 75 amps per square foot, based on the surface area of ​​the substrate 456, for a duration of about 1 second to about 30 seconds. For example, the anode strike can be performed at a current density of about 120 amps per square foot, based on the surface area of ​​the substrate 456, for about 10 seconds.

[0067] The cathodic strike (strike plating) can be performed at various current densities and durations without departing from the scope of the present disclosure. In one expression, the cathodic strike can be performed at a current density ranging from about 80 amps per square foot to about 160 amps per square foot, based on the surface area of ​​the substrate 456, for a duration of about 30 seconds to about 10 minutes. For example, the cathodic strike can be performed at a current density of about 120 amps per square foot, based on the surface area of ​​the substrate 456, for about 5 minutes.

[0068] Once the current source 460 has stopped operating, the substrate 456 can be disconnected from the current source 460 and removed from the electrolyte solution 454. The substrate 456 can then be rinsed with a rinsing fluid (e.g., deionized water).

[0069] Electroplating A variety of electrodeposition processes can be used in the method 10 of Figure 1 without departing from the scope of the present disclosure. However, a specific tin-bismuth electrodeposition method has been disclosed which, when used following any of the activation methods according to the present disclosure and the disclosed nickel strike plating method, provided excellent bonding to the substrate upon subsequent plating (see Figure 2).

[0070] 10 and 11, the disclosed electrodeposition method (generally designated 500) may begin at block 502 (FIG. 10) and includes preparing a bath 552 including an electrolyte solution 554, as shown in FIG. 11. The bath 552 and activation solution 554, along 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 on a substrate 556.

[0071] The substrate 556 can be a titanium substrate, such as a titanium mechanical fastener, etc. Other metallic substrates 556, such as iron substrates, copper substrates, and nickel substrates (e.g., Inconel), can also be used with the disclosed electrodeposition method 500 and system 550 without departing from the scope of the present disclosure.

[0072] The anode 558 of the disclosed electrodeposition system 550 can be a tin anode (e.g., 99.99 percent pure tin) or a tin-bismuth anode. As one general example, the anode 558 can include about 2 weight percent to about 5 weight percent bismuth, with the remainder being essentially tin. As one specific example, the anode 558 can include about 3 weight percent bismuth, with the remainder being essentially tin.

[0073] Bath 552 can be any container suitable for receiving and containing electrolyte solution 554. Compositionally, the materials forming bath 552 must be chemically compatible with activation solution 554. Of course, bath 552 must be sized and shaped to receive anode 558 and substrate 556 therein.

[0074] The electrolyte solution 554 contains water (HO), a tin salt dissolved in water, a bismuth salt dissolved in water, and an acid. The electrolyte solution 554 can 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 (about 21°C)). However, higher and lower pressures, as well as higher and lower temperatures, are contemplated without departing from the scope of the present disclosure.

[0075] The tin salt in the electrolyte solution 554 is tin (tin(II) 2+ ) ions. In one formulation, the tin salt in electrolyte solution 554 is tin sulfate (SnSO4). In another formulation, the tin salt in electrolyte solution 554 is tin chloride (SnCl2). In another formulation, the tin salt in electrolyte solution 554 is tin fluoride (SnF2). In yet another formulation, the tin salt in electrolyte solution 554 includes at least two of tin sulfate (SnSO4), tin chloride (SnCl2), and tin fluoride (SnF2).

[0076] The stannous salt in the electrolyte solution 554 may be present at a concentration of about 15 grams per liter to about 200 grams per liter, based on the total volume of the activation solution 554. Expressed alternatively, the concentration of the stannous salt ranges from about 15 grams per liter to about 150 grams per liter, based on the total volume of the electrolyte solution 554. Expressed alternatively, the concentration of the stannous salt ranges from about 15 grams per liter to about 100 grams per liter, based on the total volume of the electrolyte solution 554. Expressed alternatively, the concentration of the stannous salt ranges from about 20 grams per liter to about 100 grams per liter, based on the total volume of the electrolyte solution 554. Expressed alternatively, the concentration of the stannous salt ranges from about 20 grams per liter to about 50 grams per liter, based on the total volume of the electrolyte solution 554. Expressed as yet another alternative, the concentration of the stannous salt is in the range of about 25 grams per liter to about 35 grams per liter, based on the total volume of the electrolyte solution 554.

[0077] The bismuth salt in the electrolyte solution 554 is bismuth (Bi 3+ ) ions. In one formulation, the bismuth salt in electrolyte solution 554 is bismuth sulfate (Bi2(SO4)3. In another formulation, the bismuth salt in electrolyte solution 554 is bismuth oxide (Bi2O3). In another formulation, the bismuth salt in electrolyte solution 554 is bismuth nitrate (Bi(NO3)3). In another formulation, the bismuth salt in electrolyte solution 554 is bismuth chloride (BiCl3). In another formulation, the bismuth salt in electrolyte solution 554 is bismuth trifluoride (BiF3). In yet another formulation, the bismuth salt in electrolyte solution 554 includes at least two of bismuth sulfate (Bi2(SO4)3), bismuth oxide (Bi2O3), bismuth nitrate (Bi(NO3)3), bismuth chloride (BiCl3), and bismuth trifluoride (BiF3).

[0078] The bismuth salt in the electrolyte solution 554 may be present at a concentration of about 0.25 grams per liter to about 10 grams per liter, based on the total volume of the activation solution 554. Expressed alternatively, the concentration of the bismuth salt ranges from about 0.25 grams per liter to about 5 grams per liter, based on the total volume of the electrolyte solution 554. Expressed alternatively, the concentration of the bismuth salt 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. Expressed alternatively, the concentration of the bismuth salt ranges from about 0.25 grams per liter to about 1 gram per liter, based on the total volume of the electrolyte solution 554. Expressed alternatively, the concentration of the bismuth salt 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. Expressed alternatively, the concentration of the bismuth salt is in the range of about 0.4 grams per liter to about 4 grams per liter, based on the total volume of the electrolyte solution 554. Expressed further alternatively, the concentration of the bismuth salt is in the range of about 0.4 grams per liter to about 0.7 grams per liter, based on the total volume of the electrolyte solution 554.

[0079] The acid lowers the pH of the electrolyte solution 554. In one formulation, the acid in the electrolyte solution 554 is sulfuric acid (H2SO4). In another formulation, the acid in the electrolyte solution 554 is sulfamic acid (H3NSO3). In yet another formulation, the acid in the activation solution 554 includes both sulfuric acid (H2SO4) and sulfamic acid (H3NSO3).

[0080] 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed alternatively, 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. Expressed as yet another alternative, the concentration of the acid ranges from about 90 milliliters per liter to about 110 milliliters per liter, based on the total volume of the electrolyte solution 554 .

[0081] Additional components may be included in electrolyte solution 554 without departing from the scope of the present disclosure. Various carriers and / or additives may be included in electrolyte solution 554. As one specific, non-limiting example, electrolyte solution 554 may include TIN MAC HT STARTER A (a proprietary surfactant, commercially available from MacDermid of Waterbury, Connecticut). As another specific, non-limiting example, electrolyte solution 554 may include TIN MAC HT STARTER B (a proprietary methacrylic acid source, commercially available from MacDermid of Waterbury, Connecticut). As yet another specific, non-limiting example, electrolyte solution 554 may include TIN MAC HT REPLENISHER (a proprietary dipropylene glycol methyl ether source and surfactant, commercially available from MacDermid of Waterbury, Connecticut).

[0082] As one specific, non-limiting example, the electrolyte solution 554 includes water, 30 grams per liter of tin sulfate (SnSO), 0.58 grams per liter of bismuth sulfate (Bi(SO)), 105 milliliters per liter of sulfuric acid (HSO), 20 milliliters per liter of TIN MAC HT STARTER A, 5 milliliters per liter of TIN MAC HT STARTER B, and 3 milliliters per liter of TIN MAC HT REPLENISHER.

[0083] The electrolyte solution 554 can be produced in a variety of ways without departing from the scope of the present disclosure. In one particular implementation, a method according to the present disclosure for producing the electrolyte solution 554 comprises the following steps: (1) mixing an acid (e.g., 66 Baume sulfuric acid) with water (e.g., deionized water) to obtain an acidic solution; (2) dissolving a tin salt (e.g., tin sulfate (SnSO4)) in an acid solution; (3) dissolving a bismuth salt (e.g., bismuth sulfate (Bi2(SO4)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 necessary, to bring the electrolyte solution 554 to the required total volume. Includes:

[0084] In block 504 (FIG. 10), a substrate 556 is immersed (e.g., completely submerged) in an electrolyte solution 554. A conductive wire 566 can electrically connect the immersed substrate 556 to a first terminal 562 of a current source 560.

[0085] In block 506 (FIG. 10), the anode 558 is immersed (e.g., completely submerged) in the electrolyte solution 554. A conductive wire 568 can be electrically connected between the immersed anode 558 and a second terminal 564 of a current source 560.

[0086] In block 508 (FIG. 10), a current source 560 is activated such that an electric current passes between the substrate 556 and the anode 558. The electric current causes a tin-bismuth alloy to be deposited on the substrate 556.

[0087] The current passing step (block 508) can 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 that selecting an appropriate current density requires consideration of various factors, such as the duration of the current passing step (block 508), among other factors. Expressed in one manner, the current passed during the current passing step (block 508) can have a current density ranging from about 10 amps per square foot to about 80 amps per square foot, based on the surface area of ​​the substrate 556. Expressed in another manner, the current passed during the current passing step (block 508) can have a current density ranging from about 10 amps per square foot to about 50 amps per square foot, based on the surface area of ​​the substrate 556. Alternatively expressed, the current passed during the current passing step (block 508) can have a current density ranging from about 20 amps per square foot to about 40 amps per square foot, based on the surface area of ​​substrate 556. Alternatively expressed, the current passed during the current passing step (block 508) can have a current density ranging from about 15 amps per square foot to about 30 amps per square foot, based on the surface area of ​​substrate 556. Alternatively expressed, the current passed during the current passing step (block 508) can have a current density of about 30 amps per square foot, based on the surface area of ​​substrate 556.

[0088] The current passing step (block 508) can be performed for various durations without departing from the scope of the present disclosure. Those skilled in the art will appreciate that current density is a controllable parameter and that selecting an appropriate duration requires consideration of various factors (e.g., current density, among other factors). In one expression, the current passing step (block 508) can be performed for about 5 minutes to about 120 minutes. In another expression, the current passing step (block 508) can be performed for about 5 minutes to about 60 minutes. In another expression, the current passing step (block 508) can be performed for about 10 minutes to about 30 minutes. In another expression, the current passing step (block 508) can be performed for about 10 minutes to about 20 minutes. In yet another expression, the current passing step (block 508) can be performed for about 15 minutes.

[0089] In block 510 (FIG. 10), the substrate 556 is disconnected from the current source 560 and removed from the electrolyte solution 554.

[0090] In block 512 (FIG. 10), the substrate 556 may be rinsed with a rinsing fluid. As one example, the rinsing fluid may be water, such as deionized water.

[0091] Examples of the disclosure may be described in the context of an aircraft manufacturing and operation method 1000 shown in FIG. 12 and an aircraft 1002 shown in FIG. 13. During pre-manufacturing, the aircraft manufacturing and operation method 1000 may include specification and design 1004 of the aircraft 1002 and material procurement 1006. During manufacturing, component / subassembly manufacturing 1008 and system integration 1010 of the aircraft 1002 occurs. The aircraft 1002 may then be inspected, transported 1012, and placed into service 1014. While operated by a customer, the aircraft 1002 is scheduled for routine maintenance and operation 1016, which may include modifications, rebuilds, refurbishments, etc.

[0092] Each step of operational method 1000 may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this specification, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors; a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers; and a worker may be an airline, a leasing company, a military organization, a service organization, etc.

[0093] 13 , an aircraft 1002 produced according to exemplary method 1000 may include an airframe 1018 having 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. One or more other systems may also be included.

[0094] The compositions and methods disclosed herein may be used during one or more stages of aircraft production and operation method 1000. As one example, components or subassemblies 1008 corresponding to component / subassembly manufacturing, system integration 1010, and / or maintenance and operation 1016 may be manufactured or produced using the compositions and methods disclosed herein. As another example, airframe 1018 may be constructed using the compositions and methods disclosed herein. One or more example apparatuses, example methods, or a combination thereof may also be utilized during component / subassembly manufacturing 1008 and / or system integration 1010, such as by significantly speeding aircraft assembly or reducing the cost of aircraft 1002 (e.g., airframe 1018 and / or interior 1022). Similarly, one or more example systems, example methods, or a combination thereof may be utilized while aircraft 1002 is in service, such as, but not limited to, for maintenance and operation 1016.

[0095] The present disclosure further includes the following illustrative, non-limiting examples, which may or may not be included in the scope of the claims.

[0096] Example 1: An activation solution contains water, an ammonium salt with a fluorine-containing anion, and sulfuric acid.

[0097] Example 2: The activation solution according to Example 1, wherein the ammonium salt is ammonium bifluoride.

[0098] Example 3: An activation solution according to example 1 or 2, wherein the ammonium salt is ammonium tetrafluoroborate.

[0099] Example 4: An activation solution according to any of Examples 1 to 3, wherein the ammonium salt is present at a concentration ranging from about 40 grams per liter to about 100 grams per liter, based on the total volume of the activation solution.

[0100] Example 5: An activation solution according to any of Examples 1 to 4, wherein the ammonium salt is present at a concentration of about 80 grams per liter, based on the total volume of the activation solution.

[0101] Example 6: The activation solution of any of Examples 1 to 5, wherein the sulfuric acid is present in a concentration ranging from about 5 volume percent to about 25 volume percent, based on the total volume of the activation solution.

[0102] Example 7: The activation solution of any of Examples 1 to 6, wherein the sulfuric acid is present at a concentration of about 10 volume percent, based on the total volume of the activation solution.

[0103] Example 8: A method of pretreating a substrate prior to depositing a material onto the substrate, the method comprising immersing the substrate in the activating solution of Example 1 for a predetermined period of time.

[0104] Example 9: The method according to Example 8, wherein the substrate is a titanium substrate and the predetermined time is a time from about 5 seconds to about 120 seconds.

[0105] Example 10: The method according to Example 8 or 9, wherein the substrate is a titanium substrate and the predetermined time is a time of about 20 seconds to about 40 seconds.

[0106] Example 11: Furthermore removing the substrate from the activation solution after a predetermined time has elapsed; and After removal, the substrate is rinsed with a rinse fluid. The method of any of Examples 8 to 10, comprising:

[0107] Example 12: The method of Example 11, wherein the rinsing fluid is deionized water.

[0108] Example 13: The method of Example 8, further comprising subjecting the substrate to an anodic sulfuric acid process after immersion.

[0109] Although the compositions and methods disclosed herein are described in the context of aircraft, one of ordinary skill in the art will readily appreciate that the disclosed compositions and methods have utility in a variety of applications. For example, the disclosed compositions and methods can be implemented in a variety of vehicle types, including, for example, helicopters, passenger ships, automobiles, marine products (ships, motors, etc.), and the like.

[0110] While the disclosed compositions and methods for activating metal substrates have been described and illustrated in various ways, modifications may be made by those skilled in the art upon reading this specification, and the present application includes such modifications, limited only by the scope of the claims.

Claims

1. An activation solution for activating a metal substrate, comprising: Water and an ammonium salt containing ammonium tetrafluoroborate; Sulfuric acid and wherein the activation solution removes an oxide layer on the metal substrate.

2. 10. The activation solution of claim 1, wherein the ammonium salt is present at a concentration ranging from 10 grams per liter to 150 grams per liter, based on the total volume of the activation solution.

3. 3. The activation solution of claim 2, wherein the ammonium salt is present at a concentration ranging from 20 grams per liter to 120 grams per liter, based on the total volume of the activation solution.

4. 4. The activation solution of claim 1, wherein the sulfuric acid is present in a concentration ranging from 1 percent to 70 percent by volume, based on the total volume of the activation solution.

5. 5. The activation solution of claim 4, wherein the sulfuric acid is present in a concentration ranging from 2 volume percent to 50 volume percent, based on the total volume of the activation solution.

6. 6. The activation solution of any one of claims 1 to 5, maintained at atmospheric pressure and at a temperature in the range of 15°C to 50°C.

7. 7. A method for producing an activation solution according to any one of claims 1 to 6, comprising: mixing sulfuric acid with at least a portion of the water to obtain an acidic solution; and Dissolving the ammonium salt in the acidic solution A method comprising:

8. 1. A method for pretreating a substrate prior to depositing a material thereon, comprising: Immersing the substrate in an activation solution according to any one of claims 1 to 6 for a predetermined period of time. A method comprising:

9. removing the substrate from the activation solution after a predetermined time has elapsed; and After removal, rinsing the substrate with a rinsing fluid. The method of claim 8 further comprising:

Images