Its alloys are lighter but as strong as steel. Hence, titanium makes a variety of items, from medical equipment to knives and bike frames.
Naturally, titanium has an oxide layer coating. Titanium anodizing is the process of varying that oxide layer using voltage. The result is a wide range of colors depending on the voltage used. This color is fade-resistant and lasts for years. And, you can do this awesome experiment at home. The apparatus and chemicals needed are readily available at your local store.
Below is the procedure for anodizing titanium.
What is Anodization?
Anodization is an electrochemical process that involves immersing the metal in an electrolyte solution and applying a voltage to it. The metal becomes the anode or positive electrode, and the electrolyte solution becomes the cathode or negative electrode. As a result of the voltage applied, oxygen ions are attracted to the surface of the metal, and they react with the metal atoms to form a thick, protective oxide layer.
Which Metals Can be Anodized?
Many metals can be anodized, including aluminum, titanium, magnesium, and niobium. However, the anodization process does vary slightly depending on the type of metal being used. In this article, we will be focusing on the anodization of titanium.
What You Need
- Titanium (maybe your bike frame, a knife, or simply a block of titanium metal)
- Anodizing power supply (or a couple of 9v batteries)
- Non-reactive containers (plastic containers are good to go)
- Simple Green or another degreaser
- Ultrasonic cleaning machine
- Whink Rust Stain Remover (or weak sulphuric acid)
- Borax (as an electrolyte)
- Hot water
- A piece of non-reactive metal
- Alligator clips
- Paper Towels
Important Things to Note
Before we get to the procedure, take note of these cautionary things:
- You cannot go back to a color of a lower voltage once you get another color over it.
- In case you don’t like the final color, scrub off the anodized layer using high grit sandpaper. Or apply elbow grease and buff it out.
- Titanium anodizing involves electricity and toxic chemicals. Take all the precautions to avoid injuries during this experiment.
- Check if anodizing your knife or bike voids its warranty.
- The immersed area of the cathode should be bigger than that of the anode (the piece you are anodizing).
- While anodizing, there will be a release of hydrogen in the air, work in a well-ventilated area because hydrogen is flammable.
- For the anode, mainly use titanium, niobium, or tantalum for best results. Other metals may suck away the current needed for good results.
- The anode (positive) and the cathode (negative) should never touch or short-circuit stain your anode.
- For environmental safety, store your electrolyte for reuse or dilute further and use it in your garden. Rubbermaid containers are suitable for storage.
- The voltage determines the final color, but the anodizing speed depends on the current; more amperes oxidize faster.
- The voltage needed ranges from 10 to 120 for the possible colors you can achieve with anodizing titanium. Some stains require special procedures to accomplish. And as you get to high voltages, the process becomes costly and requires expertise.
How Do You Know Its Titanium
Titanium shares a property or two with metals like aluminum and stainless steel. How then do you know that piece of metal you are about anodizing is titanium? Tips:
- Unlike aluminum, titanium is very tough and doesn’t scratch easily.
- Titanium is non-magnetic and non-reactive.
- Titanium polishes well and has a deeper grey than steel
- A quick test is by smelling the metal. Titanium has no smell even after rough rubbing.
- Titanium can be made in various colors.
Once you are sure you got titanium in your hands, let’s get to business.
With all your apparatus and chemicals ready, let’s anodize titanium. Glove your hands and follow the process below.
- Prepare your working space and do the required cleaning
- If you are anodizing a knife, disassemble it
- Clean the titanium part you want to anodize thoroughly with Simple Green. Remember any dirt marks will show in the final product. Rinse the cleaned titanium parts with water. Remember to wear clean gloves to avoid leaving stains on the titanium. If the knife had prior anodizing, dip it in Whink (weak acidic solution) for several seconds.
- Mixing the electrolyte:
Put your borax in the plastic cup and add the hot water, a small quantity at a time while stirring with a spoon. Mix until the borax is well-saturated (5g/l) and fully dissolved. Other readily available chemicals to use as an electrolyte are trisodium phosphate (wall-washing chemical found in the paint department in your local store) and ammonium phosphate (lawn fertilizer). Chlorides, nitrates, and sulfates are also suitable electrolytes but avoid using them.
- Wiring and battery setup:
Connect your batteries in series to get the total voltage corresponding with the color you want. Use the anodizing color chart to get the correct voltage. If using a power supply, adjust the output voltage accordingly. Clip the two terminals of your battery array or power supply using the alligator clips.
- Connect the negative terminal alligator clip to the piece of non-reactive metal and dip it in the solution.
- Attach the part you want anodizing to the positive terminal alligator clip (anode). Remember: clean the workpiece thoroughly, and you shouldn’t immerse any non-titanium part of the anode.
- Depending on the voltage of your batteries, the respective color should form on the anode. Adding more voltage makes the anode change color. Remember, big titanium pieces require more time to anodize fully. Be sure to watch out for burns on your workpiece as you increase the voltage. Use fuses or power resistors to have some control. The color ranges from bronze at 10 volts to bright Green at 110 volts.
Types of Titanium Anodizing
There are three types of titanium anodizing. The most popular and easy to do are type 2 and 3. Type 1 is less common because it requires special high-temperature conditions.
- Type 2 titanium anodizing – Type 2 anodizing creates a wear-protection layer over the titanium, to improve lubricity. SAE International regulates type 2 titanium anodizing processes, and AMS 2488D is the set industry-specified anodizing line.
Type 2 anodized titanium is resistant to corrosion by salt water and humidity. It also withstands high temperatures. Thus, very popular in aircraft and ship manufacturing.
- Type 3 titanium anodizing – This type of titanium anodizing is also called color anodizing. It’s mainly done for color coding parts for easy visual identification. For example, the orthopedic parts vary in width and length depending on the intended area of use. To differentiate them visually, they are anodized into different colors. So, the surgeon can request a blue screw without specifying the 12mm length of the bone screw.
Type 3 titanium anodizing has wide applications in jewelry manufacturing. And the procedure described here is for type 3 titanium anodizing. Unlike type 2, type 3 has no industry standard. Each manufacturer builds its process to suit their needs.
Key differences between Type 2 and Type 3 Titanium Anodizing
Titanium finishes differ significantly between Type 2 and Type 3 titanium anodizing.
|Type 2||Type 3|
|Primary Benefit||Avoid friction between metal surfaces||Provide quick visual identification of parts|
|Specification||AMS 2488||None defined|
|Biocompatible with medical device implants||Yes||Yes|
|Improved wear resistance||Yes||No|
|Anti-galling / increased lubricity||Yes||Some|
|Color||Gray||Variety of colors.|
The typical range includes: SilverBronzePurpleBlueLight BlueGoldRoseMagentaTealGreen
More Simple Ways Concerning Anodizing Titanium!
To anodize titanium, you will need the following:
- Titanium metal: This can be in the form of sheets, rods, or wire.
- Electrolyte solution: This can be an acid or an alkaline solution. Common electrolytes used for titanium anodization include sulfuric acid and sodium hydroxide.
- Power supply: This will be used to apply a voltage to the titanium and the electrolyte solution.
- Anodizing tank: This can be a plastic container or a stainless steel tank. It should be large enough to hold the titanium and the electrolyte solution, and it should be able to withstand the voltage applied during the anodization process.
Titanium Anodizing Process
- Clean the titanium: It is important to start with a clean surface, so the titanium should be thoroughly cleaned using a degreaser and a scouring pad.
- Prepare the electrolyte solution: Follow the manufacturer’s instructions for mixing the electrolyte solution. It is important to use the correct concentration of the electrolyte and to ensure that it is at the correct temperature.
- Set up the anodizing tank: Place the titanium in the anodizing tank and add the electrolyte solution. Make sure that the titanium is fully submerged.
- Apply the voltage: Connect the titanium to the positive terminal of the power supply and the electrolyte solution to the negative terminal. Slowly increase the voltage until the desired thickness of the oxide layer is achieved. This can take anywhere from a few minutes to a few hours, depending on the thickness of the oxide layer desired and the size of the titanium piece being anodized.
- Remove the titanium: Once the desired thickness of the oxide layer has been achieved, turn off the power supply and remove the titanium from the anodizing tank. Rinse it thoroughly with water to remove any excess electrolyte solution.
How Does Anodizing Work With Titanium?
Titanium is a unique metal in that it is highly reactive to oxygen. As a result, it forms a natural oxide layer on its surface when it is exposed to air. This oxide layer is thin, however, and it is not particularly durable. Anodization is a process that is used to increase the thickness of this oxide layer, making it more durable and improving the corrosion resistance and wear resistance of the titanium.
Anodization is an electrochemical process that involves immersing the titanium in an electrolyte solution and applying a voltage to it. The titanium becomes the anode or positive electrode, and the electrolyte solution becomes the cathode or negative electrode. As a result of the voltage applied, oxygen ions are attracted to the surface of the titanium, and they react with the titanium atoms to form a thick, protective oxide layer. The thickness of the oxide layer can be controlled by adjusting the voltage and the duration of the anodization process.
How does Titanium Coloring Work?
n addition to improving the corrosion resistance and wear resistance of titanium, anodization can also be used to create decorative finishes on the metal. This is known as color anodizing, and it involves adding a dye to the electrolyte solution before the anodization process. The dye is absorbed into the oxide layer as it is forming, giving the titanium a colored finish.
There are several ways to add color to titanium through anodization, including:
- Adding a water-soluble dye to the electrolyte solution: This is the most common method for adding color to titanium. The dye is absorbed into the oxide layer as it is forming, and it is sealed into the layer by heating the titanium after the anodization process.
- Using a physical vapor deposition (PVD) process: This involves vaporizing a metal or compound and depositing it onto the titanium surface. The PVD process can be used to create a range of colors, including gold, rose gold, and black.
- Using electrolytic coloring: This involves applying a voltage to the titanium in a separate electrolyte solution after the anodization process. The voltage causes the dye to be absorbed into the oxide layer, creating a range of colors.
Frequently Asked Questions
Titanium anodizing is an electrochemical process that modifies the oxide layer on the surface of a titanium part via electric current. It is used to add color, increase wear and corrosion resistance, and alter surface properties.
You will need a titanium part, an electrolyte solution (such as sulfuric acid), an electrical current, and a power source. Depending on the desired result, you may also need to dye and seal the part after anodizing.
To clean and degrease a titanium part before anodizing, you should use a degreasing solvent or detergent to remove any dirt, oils, or other contaminants. It is important to completely dry the part after cleaning to ensure it does not interfere with the anodizing process.
The purpose of electrifying the electrolyte solution is to create an electric field that will cause the oxidation reaction of the titanium part. This will create the desired oxide layer on the surface of the part.
During titanium anodizing, you should monitor and control pH levels by using a pH meter or test strips. Keeping pH levels within a certain range can help ensure that the oxide layer grows properly and evenly on the surface of the titanium part.
Titanium has the strength and durability needed in the manufacture of many types of equipment. At the same time, titanium forms a natural oxide layer. The process of anodizing creates this layer faster and thicker to improve titanium’s lubricity, durability, and aesthetic properties.
Type 3 anodizing is easy to perform at home with local store-available chemicals and apparatus. You should take special care with the chemicals and electricity; they are life-threatening if mishandled. Do enough research on safety measures before dealing with these chemicals and electricity, besides, no one needs hospitalization.
The titanium anodizing process above will undoubtedly make your knife look great. To vary the patterns, use some masking using tape or vinyl. Happy anodizing.