Tom Anderson
Newly Enlightened
Since I'm a new member here, I thought I'd share my mini-tutorial on anodizing titanium.
The photos show some of the knives I once built, but the principles apply to other titanium gadgets as well.
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The process of anodizing titanium involves immersing the object to be colored in a container with a titanium cathode inserted and filled with an electrolyte. Passing a DC charge through the electrolyte solution will cause a microscopic oxide film to adhere to the part. The thickness of the oxide film determines the color.
Attached is a color chart that lists the various colors obtainable through the various effective DC voltage ranges:
Note that these colors can also be obtained by heating the part to create the oxidation, but that process is not as accurately controlled.
The equipment used consists of the following:
1. A DC power supply that has a range of 0 to 125 volts. The wattage (amperage x voltage) of the power supply will determine the size of the part that can be anodized as well as the speed of anodization. For most knife handles (approximately 6" long or smaller), I would recommend using a 1-kilowatt DC power supply (approximately 7 amps x 150 volts).
2. A non-conductive container, large enough for the cathode (see #3) and the part to be anodized.
3. A strip of titanium to be used as a cathode. The surface area of this strip must be greater than the surface area of the part being anodized. For safety, the cathode can be covered with nylon webbing to avoid accidental contact with the part during immersion.
4. Electrolyte solution. This can be a simple solution of 5% trisodium phosphate in distilled water – enough to fill within 1" of the top of the container.
5. Leads for the + and – terminals between the DC power supply, cathode (titanium strip), and anode (see below).
6. Anode: This is a small hook made from titanium wire to which the part is attached for immersion.
7. Thick rubber gloves to be worn as a safety measure during the anodizing process.
8. A bottle of cleaner (Windex ammonia-based window cleaner works well).
9. A small paintbrush with a metal ferrule. This is used for reverse-polarity brush anodizing described later.
Equipment setup and use:
NOTE: Exercise caution when working with the power supply turned on to avoid electrocution. Always wear rubber gloves when the power supply is turned on. Do not attempt this process while working on an electrically conductive surface!
Fill the container with the 5% TSP/distilled water solution (electrolyte). Attach the cathode (-) lead from the DC power supply to the cathode – making sure the connection is well above the electrolyte level.
Attach the anode (+) lead to the titanium hook. Exercise caution not to bring the two leads together.
Turn on the power supply and adjust the voltage to achieve the color (as shown on the attached chart). Turn the power supply off.
Clean the part to be anodized with the ammonia based cleaner. Attach the part to the titanium hook/anode, and submerse it in the electrolyte bath.
Turn the DC power supply on until the color appears on the part. Turn the DC power supply off when the color is achieved and before removing the part from the electrolyte bath.
Re-clean and dry the part to remove any traces of electrolyte.
Multi-Stage Anodizing:
Applying different colors to a titanium part can be achieved using the equipment listed previously with several different techniques. Besides ensuring safety, the most important thing to remember is that the oxide film (color) applied during a higher voltage session will remain when applying an oxide film (color) at a lower voltage setting. For instance, you can submerge a titanium part that had been partially masked when a 40 DCV color (powder blue) was applied and apply a 25 DCV color (purple) without affecting the powder blue color.
I have attached several photos illustrating the results of various multi-stage anodized titanium parts.
This knife has had multi-stage anodized scales that were accomplished with the following (basic) steps:
1. Anodize the engraved bolster area with gold at 15VDC. Sand off the top to make it look like gold-filled engraving.
2. Mask off the engraved bolster area, apply a light coat of spray glue to the "overlay" area.
3. Anodize the light blue color at 43VDC.
4. Remove the spray glue and reapply another light coat.
5. Anodize the dark blue color at 28VDC
6. Remove the spray glue.
7. Anodize the purple color at 19VDC.
NOTE: All parts were anodized using the immersion method described previously. The stepped pivot screw collar is a separate piece, anodized at 28VDC.
This is another example of multi-stage anodizing. Here the overlays were anodized at 65VDC to achieve the green-gold color in the file work. Then, the tops of the overlays were sanded, cleaned, and re-anodized at 28VDC to achieve the blue color.
The photos show some of the knives I once built, but the principles apply to other titanium gadgets as well.
******************************
The process of anodizing titanium involves immersing the object to be colored in a container with a titanium cathode inserted and filled with an electrolyte. Passing a DC charge through the electrolyte solution will cause a microscopic oxide film to adhere to the part. The thickness of the oxide film determines the color.
Attached is a color chart that lists the various colors obtainable through the various effective DC voltage ranges:
Note that these colors can also be obtained by heating the part to create the oxidation, but that process is not as accurately controlled.
The equipment used consists of the following:
1. A DC power supply that has a range of 0 to 125 volts. The wattage (amperage x voltage) of the power supply will determine the size of the part that can be anodized as well as the speed of anodization. For most knife handles (approximately 6" long or smaller), I would recommend using a 1-kilowatt DC power supply (approximately 7 amps x 150 volts).
2. A non-conductive container, large enough for the cathode (see #3) and the part to be anodized.
3. A strip of titanium to be used as a cathode. The surface area of this strip must be greater than the surface area of the part being anodized. For safety, the cathode can be covered with nylon webbing to avoid accidental contact with the part during immersion.
4. Electrolyte solution. This can be a simple solution of 5% trisodium phosphate in distilled water – enough to fill within 1" of the top of the container.
5. Leads for the + and – terminals between the DC power supply, cathode (titanium strip), and anode (see below).
6. Anode: This is a small hook made from titanium wire to which the part is attached for immersion.
7. Thick rubber gloves to be worn as a safety measure during the anodizing process.
8. A bottle of cleaner (Windex ammonia-based window cleaner works well).
9. A small paintbrush with a metal ferrule. This is used for reverse-polarity brush anodizing described later.
Equipment setup and use:
NOTE: Exercise caution when working with the power supply turned on to avoid electrocution. Always wear rubber gloves when the power supply is turned on. Do not attempt this process while working on an electrically conductive surface!
Fill the container with the 5% TSP/distilled water solution (electrolyte). Attach the cathode (-) lead from the DC power supply to the cathode – making sure the connection is well above the electrolyte level.
Attach the anode (+) lead to the titanium hook. Exercise caution not to bring the two leads together.
Turn on the power supply and adjust the voltage to achieve the color (as shown on the attached chart). Turn the power supply off.
Clean the part to be anodized with the ammonia based cleaner. Attach the part to the titanium hook/anode, and submerse it in the electrolyte bath.
Turn the DC power supply on until the color appears on the part. Turn the DC power supply off when the color is achieved and before removing the part from the electrolyte bath.
Re-clean and dry the part to remove any traces of electrolyte.
Multi-Stage Anodizing:
Applying different colors to a titanium part can be achieved using the equipment listed previously with several different techniques. Besides ensuring safety, the most important thing to remember is that the oxide film (color) applied during a higher voltage session will remain when applying an oxide film (color) at a lower voltage setting. For instance, you can submerge a titanium part that had been partially masked when a 40 DCV color (powder blue) was applied and apply a 25 DCV color (purple) without affecting the powder blue color.
I have attached several photos illustrating the results of various multi-stage anodized titanium parts.
This knife has had multi-stage anodized scales that were accomplished with the following (basic) steps:
1. Anodize the engraved bolster area with gold at 15VDC. Sand off the top to make it look like gold-filled engraving.
2. Mask off the engraved bolster area, apply a light coat of spray glue to the "overlay" area.
3. Anodize the light blue color at 43VDC.
4. Remove the spray glue and reapply another light coat.
5. Anodize the dark blue color at 28VDC
6. Remove the spray glue.
7. Anodize the purple color at 19VDC.
NOTE: All parts were anodized using the immersion method described previously. The stepped pivot screw collar is a separate piece, anodized at 28VDC.
This is another example of multi-stage anodizing. Here the overlays were anodized at 65VDC to achieve the green-gold color in the file work. Then, the tops of the overlays were sanded, cleaned, and re-anodized at 28VDC to achieve the blue color.
