How to Spot Anodize Niobium and Titanium

There are several ways to anodize a work piece. Using the spot anodizing process, you can create ‘painted’ and patterned designs.

Last edited: 7/18/2019

What is Anodizing?
Niobium and titanium react to exposure to oxygen by forming a clear oxide layer on their exposed surfaces. Anodizing causes this reaction to continue further than it would naturally, producing thicker layers of oxide. As the layer thickens, it begins to interrupt the light waves as they pass through and reflect off the metal surface. This interference creates color. Since the thickness of the oxide controls the color that is produced, and since anodizing controls the thickness, the color produced in a given jewelry piece becomes controllable through the anodizing process.

There are several ways to anodize a work piece. Using the spot anodizing process, you can create ‘painted’ and patterned designs. Using the bath anodizing process, you can create a single, solid color or you can create a rainbow effect or multiple solid-color blocks. Instructions for spot anodizing are below; to learn how to apply ‘painted’ or patterned designs, see our “How To Bath Anodize Titanium” instructions.


Finishing Your Piece 

To the greatest extent possible, complete all surface finishing on the jewelry piece before anodizing. The layer that is responsible for the color (the anodized layer) is comparatively thin, and it’s easy to remove it inadvertently in processes such as sanding and buffing.

If you are working with titanium you will need to complete a diligent and aggressive cleaning procedure prior to anodizing using a metal etch. Anodizing niobium does not require this step.

Creating a texture on the metal surface, or creating a ‘tooth,’ with Scotch-Brite™ pads or sandpaper before anodizing will cause the surface to reflect light a bit differently than if the surface were polished.

A matte finish results in colors that are slightly less bright, but the color is less affected by the angle from which the jewelry is viewed because the uneven surface scatters the light rays over a wider area. A highly polished surface delivers brighter color but is more affected by the angle of viewing. 

Based on your design, you can play with how the light travels and reflects. Sanding or scratching in different directions can reflect the light differently, displaying a range of interesting effects. Before anodizing the niobium, make sure it is scrupulously clean--dirt, dust, oils and so on interfere with the anodizing process. You can use alcohol to wipe the surface clean of these contaminants.


Mixing the Electrolyte Solution

To mix the anodizing electrolyte solution, we use TSP-PF granules, a phosphate-free soap that is environmentally friendly. Dissolved in pure water (distilled or demineralized), TSP-PF produces a non-foaming soapy solution rich in electrolytes, ideal for anodizing. Tap water almost invariably contains minerals that can cause defects in the oxide layer as it forms on the surface of the metal; we don't recommend using it. 

Mix a small amount of the electrolyte solution according to the manufacturer’s directions and place in a small plastic or glass (non-conductive) container.


Preparing the Work Piece

Lay the work piece front side down on a flat surface and tape a piece of thin, stainless steel foil or wire to the back of the piece, making sure that the wire or foil against the work piece is completely sealed by the tape so that the electrolytic solution cannot reach it. Leave a length of foil or wire extending out from the piece that is long enough to allow the clip of the red (positive) lead to be attached.


Preparing the Applicator

Connect the black (negative) lead to the applicator material. If a sponge, fabric bundle, or other such material is used, simply connect the alligator clip to the material. If a paintbrush is used, connect the lead to the metal ferrule by clipping onto it or by removing the clip and soldering the wire directly to the ferrule. Any metal, including a paintbrush ferrule, that could come into contact with the work piece must be covered with electrical tape or coated with rubber to protect against electric shock and short circuit.


Setting Up the SMT Micro Anodizer 

Read the manual of the SMT Micro Anodizer and follow all safety and start-up procedures to ensure it is functioning properly before using it. The anodizer carries up to 120 volts of electricity, and voltage that high is dangerous and can be fatal if not carefully and responsibly handled.

Before plugging in the leads, turn the micro anodizer on and make sure the voltage is at 0. This is a good habit to get into when using the micro anodizer or any high-voltage equipment.

With the anodizer OFF, connect the red (positive) lead from the output on the anodizer to the work piece where the lead emerges from the sealed back. Note that this is the reverse of the more familiar electroplating process, in which the black (negative) lead is connected to the work piece, so that the current flows to the work piece. In the anodizing process, the current flows from the work piece, so the leads are attached opposite to how they would be for a plating process.


Anodizing the Work Piece 

 Put on rubber gloves. 

Dip the applicator into the electrolyte solution and squeeze out excess moisture. In this process, the plated clip will contact the moistened applicator. If you're using a paintbrush, the solution will need a moment in the solution to allow the electrolyte to travel up to the ferrule (over time, the ferrule will corrode and the brush will need to be replaced).

Connect the black (negative) lead from the applicator to the anodizer output.

Turn the anodizer ON and, using the controls on the front of the anodizer, set the desired voltage (the current remains at "0"). The low current will slow the process to allow time to work with the necessary precision; if the process is too slow, raise the current to achieve a comfortable speed.

Touch the applicator to the work piece; the colors will begin to appear. If the applicator is held in one place, the colors begin to spread outward from that spot with the lower-voltage colors farthest out. If the applicator is moved smoothly and constantly, an even all-over color can be created. To create fine details, use a paintbrush that is almost dry.

Adjust the voltage to control the color you want; adjust the current to control the speed of the reaction based on the level of detail you’re working to create and the size of both the work piece and the applicator. With a small applicator and work piece, less current is called for. The higher the voltage, the lower the current should be.

When finished, turn the voltage down to “0” and turn the anodizer off.


Using Masks

To create patterns on a work piece with a sponge or textured applicator, you can use anodizing tape or a mask such as Mighty Mask to keep the electrolytic solution from touching certain areas of the piece while anodizing other areas.

Begin by anodizing the areas that will require the highest voltage. Once a color has been achieved at a specific voltage, exposing the metal to lower voltages will not have any effect on that color. 

1. Turn the metal front side up. Make sure the surface is clean, dust- and dirt-free. Apply tape or a mask to all areas of your work piece except the areas that are to be anodized at the highest voltage in the design.

2. To apply tape, cut piece of tape to the size and shape you want to keep from anodizing.

3. Start at one end of the metal and roll the tape on, working to prevent getting air trapped under the tape (similar to applying a protective screen to a cell phone or tint to a car window). Once the tape is applied to the surface, use a roller or burnisher to push out any air pockets.

4. Now you can use an X-acto® or other fine-tip utility knife to cut away areas of the tape, exposing the areas to be anodized. Whatever is covered by the tape will remain gray in color. Cutting the tape in this way will leave a sharp engraved line in the metal; if you do not want to have this line on the work piece, cut the tape on a clean glass surface and transfer the mask to the work piece in sections, burnishing each section carefully into place. 

5. If desired, use Scotch-Brite™ or another abrasive to add texture to the exposed surface so that it will reflect the light differently.

6. With the anodizer off, clip the red (positive) lead to the work piece and anodize it.

7. Trim away the masking as desired for the color at the next highest voltage, checking to ensure that all edges of your mask remain sealed. Anodize. 

8. Continue until your design is complete.