Can Titanium be Anodized? What You Need to Know

Titanium is a durable metal with excellent corrosion resistance properties.

But can you anodize titanium? What's the best way to do it?

Yes, titanium can be anodized, but unlike other metals where anodizing is used to enhance durability and corrosion resistance, titanium is typically anodized to achieve appealing aesthetics. For example, you can anodize titanium to attain various colors while maintaining its natural metallic appearance.

This article provides a detailed guide on anodizing titanium by going through its process, applications, and different colors available in anodized titanium.

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Anodizing Titanium - Is it Possible?

The simple answer is that titanium can be anodized.

Anodizing titanium is a popular method for adding bright colors to titanium projects without needing dyes, harsh brighteners, or other chemicals.

Titanium is a non-ferrous metal that readily acts with oxygen to form titanium oxide, and generally develops a thin layer of titanium oxide on its surface when exposed to atmospheric air.

The anodizing process increases the thickness of this layer through an electrochemical process.

In this process, the titanium component, which acts as the positive electrode (anode), is placed in a water-based electrolyte solution such as trisodium phosphate (TSP) or any other anodizing salt. 

When an electrical current is applied, the electrical potential drives the oxygen to the surface of the titanium, adding to the thin layer of titanium oxide already present on its surface. 

The thickness of the oxide layer determines the perceived color of anodized titanium.

This oxide layer is adjusted by altering the voltage and the duration of the immersion in the electrolyte solution.

Moreover, unlike aluminum anodizing, titanium does not require dyes, since its perceived color is the result of the refraction of light by its oxide layer.

However, you can use dyes or anodizing paint to get the desired anodizing color such as green anodizing, black anodizing, etc.

How to Anodize Titanium?

Steps	Description
Clean	Clean the titanium surface using solvent cleaning, chemical cleaning, or mechanical cleaning methods.
Etch	Etch the titanium surface with an acid solution to enhance adhesion and finish quality (optional).
Dry	Dry the titanium surface thoroughly.
Mask	Mask off certain areas if needed (optional).
Electrolytic Bath	Prepare the anodizing solution by mixing an electrolyte with water.
Connect wires	Set up the circuit with a cathode, and titanium workpiece at anode.
Supply Power	Turn on the power supply and set it to the desired voltage.
Anodize	Slowly immerse the titanium workpiece in the solution and apply the voltage.
Finish	Remove the titanium workpiece when its color stabilizes.

Since you’ll be dealing with chemicals and electricity, you must ensure safety during the anodization process.

Wear protective gloves and glasses, and use a respirator or fume hood if available.

This will protect you from spills and splashes and prevent any oil from getting on the workpiece through your hands.

Step 1: Clean the Workpiece

To achieve consistent color in the anodized finish of titanium, it is crucial to thoroughly clean the surface of the titanium workpiece to remove any dirt, lubricants, or other impurities. 

You can choose from various methods to clean the surface of the titanium.

Solvent cleaning is the most common method that involves using a solvent, such as acetone or methyl ethyl ketone, to dissolve or loosen contaminants on the metal surface. 

This method also helps to remove oil, grease, or wax from the metal surface.

Alkaline solutions, acidic solutions, and solvent blends can also be used for cleaning the workpiece.

Apart from that, abrasives or blasting are mechanical means to remove contaminants from the metal surface. These techniques include sandblasting, bead blasting, and ultrasonic cleaning.

After cleaning, dip the metal into distilled water, rub it with a paper towel and set it aside for drying.

Step 2: Etch the Surface of the Titanium Workpiece

Etching involves using an acid solution to remove a thin layer of the metal's surface, creating a rough, porous surface more receptive to the anodization process.

It is not always necessary to etch the titanium before anodization, but it can give your better results.

Etching can improve the adhesion of the oxide layer, create a more uniform finish, and allow for higher anodizing voltages on your titanium.

Moreover, etching can help remove surface contaminants or imperfections, creating a more durable and long-lasting finish while enhancing the visual appearance of the anodized titanium.

After completing the etching, it is required to clean the workpiece in a distilled water bath to neutralize any acids left on it.

Step 3: Dry the Titanium Workpiece

Before you begin anodizing, ensure that the metal object is thoroughly dried to prevent contamination of the anodizing solution. 

You may use compressed air, a hot air blower, or a drying oven to dry it quickly.

Step 4: Mask the Areas that are Not to be Anodized

Masking is optional and is required only if certain areas of the workpiece are not to be anodized.

You can use tape, paint, or wax to mask off certain areas to protect them from the anodizing process. 

Step 5: Prepare the Anodizing Solution

Factor	Description
Electrolyte solution	Always use a titanium-specific electrolyte solution.
Temperature and pH	Control the temperature and pH within the recommended range to avoid damaging the metal workpiece.
Voltage	Apply the appropriate voltage for the desired color.
Ventilation	Ensure proper ventilation, as anodization can release harmful gases.

The anodization solution is prepared by mixing an electrolyte, such as baking soda, with water.

You will require a tablespoon of baking soda for every cup of water or a ratio of about 1 part baking soda per 8 parts water.

Stir the solution and let the baking soda dissolve completely.

You can also use trisodium phosphate (TSP) or Borax instead of baking soda, but generally baking soda results in more vibrant colors of the anodized titanium.

Step 6: Make the Circuit

Connect the negative terminal (cathode) to a piece of titanium (such as a titanium straw), and connect the positive terminal (anode) to a titanium wire, which then connects with the titanium workpiece to be anodized.

This is done in order to prevent the anode wire (copper) from coming in contact with the anodizing solution, as it affects the quality of anodizing.

You can also use tinfoil, stainless steel, or copper wire to make ground or negative connections, but I found that these other materials consume more power.

Make sure to disconnect the wires from the power supply before immersing the workpiece into the electrolytic bath.

Step 7: Dip the Titanium in the Anodizing Bath

Now that our circuit is complete, we can begin anodizing.

Slowly submerge the titanium object into the solution, ensuring that only the titanium wire and your part touch the bath and the positive lead does not come into contact with the electrolytic bath.

Turn on the power supply and set the desired voltage.

Moreover, be careful not to touch the cathode with the anode (short circuit), as it will spot the titanium.

You will notice bubbles emerging from the solution once your part is submerged, indicating the start of the anodization process.

An additional tip is to use lower voltages first, as you can always migrate to higher voltages for other colors, but you cannot go the other way around.

The anodization process should take about 10-15 seconds only.

Take out the anodized titanium once it stops changing colors, rinse it in distilled water, and then dry it with a paper towel.

Color Options in Anodized Titanium

The color of the anodized layer can range from clear or pale yellow to various shades of blue, green, purple, or brown, depending on the electrolyte solution and the voltage you supply.

Moreover, the impurities or contaminants in the electrolyte solution can also affect the exact color.

Voltage Range (Volts)	Color
9-14	Bronze
15-19	Purple
20-24	Blue
25-29	Light Blue
30-38	Silver
39-55	Gold
56-69	Rose
70-78	Magenta
79-85	Teal
86-90	Green

Anodized Titanium Colors at Low Voltage (9-14 V)

Supplying a voltage of about 9-14 volts will result in yellow, bronze, and light to dark brown shades.

These shades are extensively used to create jewelry, such as rings, earrings, and necklaces, as these colors can give a classic and elegant look.

Anodized Titanium Colors at Medium Voltage (15-29 V)

A voltage of 15-29 will anodize your titanium to blue shades.

Blue shades are frequently used with sporting goods, such as golf clubs and bike frames, to create a sleek and modern look.

Anodized Titanium Colors at High Voltage (Above 29V)

Higher voltage colors are comparatively more costly as they require specialized equipment and more electricity.

However, anodizing titanium at these voltages yields stunning shades, including silver, rose, and green.

In addition to jewelry, these shades are used as a coating on eyeglass frames or other wearable accessories to create a unique and eye-catching appearance.

Does Anodized Titanium Wear off?

Titanium is a naturally durable and corrosion-resisting metal, so anodization is typically performed to improve its aesthetics.

However, besides adding stunning colors to the objects, anodizing also provides a tougher surface to the titanium that can protect the underlying metal from scratches and stress concentrations.

Furthermore, properly anodizing titanium will further enhance the corrosion resistance, bonding force, and biocompatibility and prevent galling, a common tendency of titanium.

Generally, anodized titanium does not wear off easily in indoor or outdoor conditions. As a result, it is widely used on applications that are meant to last, such as jewelry items, etc.

On the other hand, while the hard coating can improve durability, it may also be prone to cracking under extreme temperature fluctuations due to its lack of ductility. 

Therefore, it is essential to consider the part's intended use when deciding whether or not to use anodization.

Applications of Anodized Titanium

Anodized titanium is used in various applications due to its enhanced properties and wide range of colors compared to anodized aluminum colors.

Aerospace

Titanium and its alloys are valued in the aerospace industry for their high strength-to-weight ratio and excellent thermal capabilities.  

However, their use is limited due to the reaction of titanium with atmospheric oxygen, forming an oxide layer that often results in the jamming of mating parts in an assembly.

Anodizing adds a protective layer, reducing these undesirable properties to make titanium a perfect fit for the aerospace industry.

Chemical and Food Processing

The extreme corrosion resistance of anodized titanium makes it a good choice for use in chemical and food processing environments, where it may come into contact with corrosive substances or high moisture levels.

Medical Implants and Surgical Hardware 

Medical applications such as implants and surgical hardware frequently use anodized titanium due to its biocompatibility and ability to support bone growth.

Marine Environments 

Anodized titanium is also a good choice for marine environments, where it may be exposed to saltwater and other corrosive substances.

Color Coding Tools and Hardware

Titanium is also anodized to be used for color coding tools and hardware according to size and type, making it easier to identify and organize them.

Jewelry and Recreational Items

Anodized titanium is used to create or decorate jewelry and recreational items such as bicycles, golf clubs, and paint guns. 

Its lightweight, stunning colors and corrosion-resistant properties make it a good choice for these applications.

Final Thoughts

Titanium anodizing is generally required for professional applications where extreme durability with an aesthetically pleasing look is desirable.

However, it is a relatively straightforward process that can be done at home with the proper knowledge and the right tools.

As a result, anodizing titanium is a good choice for DIY projects such as jewelry, vases, knives, metallic tools, candle holders, etc.

Frequently Asked Questions (FAQ)

How do I care for and maintain anodized titanium?

Anodized titanium is generally low maintenance. However, to keep it in the best condition, it is recommended to clean it regularly with mild detergent and water. Avoid using abrasive cleaners or scrubbers, as these can damage the oxide layer.

Can anodized titanium be repaired or re-anodized?

Yes, anodized titanium can be repaired or re-anodized. However, it requires proper knowledge and the right tools to achieve a smooth and uniform coating over the damaged area. Apart from that, the anodized layer has poor electrical conductivity, generating the need to peel the anodized layer to provide space for electrical terminal contact.

How does anodizing affect the dimensions of metal?

The anodizing process generally does not significantly affect the dimensions of a titanium component. The oxide layer is typically a few micrometers thick and does not add significant thickness to the object. However, it can cause minor dimensional changes, such as slight distortions or shifts in the surface of the metal.