What is Titanium Anodizing?
Titanium anodizing is a process in which titanium oxides are artificially grown on top of an underlying titanium base metal using electrolysis. A very similar process can be done with aluminum, however, aluminum anodizing requires the part to be dyed in order to create the desired color. This process is usually done professionally as it can be a messy process. This dyeing process is not required with titanium because of its oxide film which refracts light differently than most other metal oxides. It acts like a thin film that reflects a specific wavelength of light depending on the thickness of the film. By varying the voltage applied during the anodization process the color of the titanium surface can be controlled. This allows titanium to be anodized to almost any color that one can think of.
Why is Anodizing important?
Besides allowing for the production of aesthetically pleasing parts, anodizing also adds a much harder surface to protect the softer base metal which is more susceptible to scratches that act as stress concentrations. These stress concentrations act as prime locations for fatigue cracking which can lead to catastrophic failure after a certain amount of stress cycles. This hard coating can also be a double-edged sword when it comes to durability as well; if the part is likely to be exposed to extreme temperature fluctuations then anodizing may be prone to cracking (because of its hard outer shell which lacks ductility). Because of this, the use of a part needs to be taken into account in order to decide if anodization is appropriate for the intended use.
There are also multiple types of anodization that result in slightly different finishes. For instance, titanium anodization is available in multiple “types” that produce slightly different finishes; the most common are types I, II, and III, Similarly aluminum can be anodized with types I, II, and III as well. All of these types of finishes result in different properties of the anodization layer.
What Can Be Anodized?
Aside from aerospace parts that are associated with anodization, Knife scales, pens, rings, jewelry, and anything else made of the following materials can be anodized:
- Aluminum and aluminum alloys
- Titanium and titanium alloys
What Does Anodized Titanium Look Like?
There are many different methods and techniques used in order to produce beautiful patterns on titanium. One of the coolest techniques is called sponge anodizing which produces a beautiful pattern. This process can be done for any titanium part. Other patterns can also be created using other unique anodization techniques.
What Do I need in Order To Anodize Titanium?
Because the anodization process is slightly different depending on the metal being anodized, we will keep to the theme of this article and talk specifically about titanium. A list of the required materials is shown below:
- 120 Volt Power supply (or 10 9 Volt batteries which you can hook up + to – in order to achieve the desired voltage (ex: 18V=2x9V batteries, etc.))
- Baking soda (this will be our electrolyte)
- small diameter titanium wire
- alligator clamps
- Whink rust stain remover (not necessary but will help ensure a durable finish; this will be used to etch the titanium)
- A piece of steel for the cathode (hydrogen gas will be generated here)
- A piece of titanium you wish to anodize
How Do I Anodize?
Before you start titanium anodizing it is worth spending some time doing research so that your parts turn out perfect. One piece of advise is to make sure your parts are 100% clean when you anodize; any skin oils, lubricants, etc., left on the surface of your titanium when you anodize can and will leave imperfections in your anodized finish. A short video demonstrating this process is shown below. Note, this process does pose an electrocution risk and care should be taken to understand how to minimize this risk.
Oxidation and reduction
The element chromium
The element cobalt
What are valence electrons?