Anodizing is an electrochemical process that grows a transparent oxide layer on the surface of titanium. The thickness of that layer, controlled precisely by voltage, determines which wavelengths of light are reflected back to the eye, producing vivid, permanent color with zero added material.
Did you know titanium isn't a noble metal and oxidizes readily when exposed to air? The result is a microscopically thin oxide layer (TiO₂) just 1–20 nanometers thick. It is actually this oxide layer that protects the titanium from further oxidation, and why titanium is known to be so corrosion-resistant even in harsh environments. Anodizing takes deliberate control of this natural oxidation reaction.
The process involves an electrolytic cell including a DC power supply, a cathode (conductive metal piece) connected to the negative terminal of the power supply, and an anode (titanium workpiece to be anodized) connected to the positive terminal, and an electrolyte solution separating the two. As current flows, the TiO₂ oxide layer on the anode is driven to grow to a precise thickness measured in nanometers, which in turn determines the color you see as a result of thin-film interference.
When light strikes the anodized titanium, it reflects off both the top and the bottom (titanium surface) of that transparent oxide film. The shift between the two reflected paths of light interfere with each other, reinforcing some color wavelengths and canceling out others depending on the layer's thickness. The resulting wavelength that is most reinforced within the spectrum is the color your eye sees. No dyes, no pigments, no coatings — the color is created from the material itself.
| Color | Approx. Voltage | Oxide Thickness |
|---|---|---|
| Copper | ~10V | ~20nm |
| Purple | ~17.5V | ~35nm |
| Blue | ~22.5V | ~45nm |
| Light Blue | ~30V | ~60nm |
| Gold | ~55V | ~110nm |
| Pink | ~62.5V | ~125nm |
| Violet | ~67.5V | ~135nm |
| Cyan | ~80V | ~160nm |
| Aqua | ~85V | ~170nm |
| Green | ~95V | ~185nm |
Note: exact voltages vary by electrolyte composition and temperature. This is a representative reference.
A simplified look inside the anodizing tank. The titanium part to be "anodized" is the anode (left); a second conductive metal plate is the cathode (right); both sit in an electrolyte solution which primarily carries current via ions and prevents voltage drop across between the anode and cathode. When the DC power supply is switched on, electrons move from the titanium (giving the Ti surface a positive charge) through the external circuit to the cathode where water (H2O) is reduced to hydrogen gas (H2), and hydroxide (OH-), which migrates back across the electrolyte bath to the anode. It is there that the OH- ions shed an O2- ion leaving an H+ ion that immediately reacts with another hydroxide OH- ion forming H2O that is returned to the electrolyte solution. Each postively charged Ti4+ ion on the surface of the anode reacts with two available O2- ions (oxidation reaction), further building the transparent TiO₂ layer from the bottom up.
Hydroxide (OH⁻) ions arriving from the bath give up their oxygen at the oxide's outer surface — every two that land leave one O²⁻ behind and return the rest to the solution as H₂O. That O²⁻ then permeates inward through the existing oxide to the titanium surface, where it meets Ti⁴⁺ drawn from the metal — two O²⁻ to each Ti⁴⁺ — to lay down another increment of TiO₂. Because it forms at the base, the layer grows from beneath. This oxidation half-reaction is the step that actually grows your color.
An alkaline bath holds almost no free protons (H+), so water (H2O) itself is reduced right at the cathode plate where it gives up a hydrogen to an electron returning through the circuit. The hydrogen atoms pair-off to form small bubbles of H₂, while the hydroxide ions left behind in the solution OH⁻ pulled toward the anode. This reduction half-reaction balances the circuit but adds nothing to the titanium part itself.
The electrolyte — often something as ordinary as trisodium phosphate (TSP) in water — only carries current between the plates. Its ions are never consumed in forming the oxide, so a single bath can color part after part.
The oxide film is transparent, so light doesn't simply bounce off it. Part of the beam reflects at the top surface, where air meets oxide; the rest passes through and reflects again at the bottom, where oxide meets titanium. Two copies of the same light head back toward your eye — and because the second one detoured through the film, they no longer march in step.
Drag the slider to change oxide thickness and watch which color emerges when the two reflected rays combine. The eye shows the resulting hue — exactly what you'd see on an anodized titanium surface at that voltage.
Resulting color
Voltage
30 V
Path difference
≈ 200 nm
The ray that reflects off the bottom travels an extra distance — roughly twice the film's thickness — before it rejoins the first. That detour, measured in nanometers, sets everything: change the thickness and you change the delay between the two waves.
Light travels as a wave. When the detour lines the two waves back up crest-to-crest, that wavelength is amplified — constructive interference. When it lands crest-to-trough, that wavelength cancels — destructive interference.
White light is every wavelength blended together. The film quietly removes some and boosts others, and the mix that survives is the hue you see — pure color pulled straight out of white light, with no pigment involved.
It's the same physics that colors a soap bubble or a film of oil on water. Because the path difference also depends on your viewing angle, the hue drifts as the part tilts in the light — and because a thicker film (higher voltage) lengthens the detour, growing the oxide walks the surface through the whole spectrum.
The same brushed-satin titanium tube, anodized across the full voltage range. No paint, no dye — every hue is the metal’s own oxide layer bending the light.
We degrease, clean, and prepare the surface. For polished finishes we polish first; for bead-blasted we blast with glass beads before anodizing. Because the oxide layer is transparent, whatever texture sits underneath shows straight through — so the finish is locked in before the color.
Threads, bearing surfaces, headset races, bottom bracket shells, and all contact surfaces are carefully masked to prevent the oxide layer from affecting critical tolerances.
The piece is submerged in our electrolyte bath and wired to the anode — the positive terminal of a precision DC supply — with a second plate as the cathode. Current flows, water splits at the surface, and the TiO₂ layer begins to grow.
We ramp voltage to the target level for your chosen color — holding it precisely until the oxide reaches the correct thickness. For multi-color designs, we mask and re-anodize at different voltages.
Anodized color won't chip, peel, or fade from UV exposure — it's part of the metal itself. The only way to remove it is mechanical abrasion.
Use mild soap and water. Avoid abrasive cleaners, steel wool, or anything that scratches. A soft microfiber cloth is ideal for polished surfaces.
Strong acids, alkalis, and solvents can damage the oxide layer. Avoid brake fluid contact, and rinse thoroughly after any chemical chain lube application.
Anodized titanium is fully weather-resistant. Rain, mud, sweat — none of it affects the color or finish. Rinse after muddy rides.
Polished surfaces can develop micro-scratches over time. A titanium-safe metal polish will restore the shine without removing the oxide layer.
Properly cared for, an anodized Ti finish will outlast the bike. We've seen 20-year-old anodized Ti components that look nearly new.
Now that you know the science — let's apply it to your design. Start with a free design consultation.