[POTUS31] had a need for anodized titanium, but the tried and true “submersion” method was not going to work out well for what he was trying to do. In order to create the look he wanted he had to get creative with some tape, a laser cutter, Coke, and a whole lot of 9v batteries.
His Ring-A-Day project has him creating customized rings based on reader feedback, and lately the requests have had him searching for a good way to color metal. Anodizing titanium was a sure bet, though creating detailed coloring on a small medium is not an easy task.
[POTUS31] figured that he could gradually anodize different areas of the ring by using laser-cut tape masks, allowing him to selectively oxidize different portions of his creations as he went along. Using the phosphoric acid prevalent in Coke as his oxidizing agent along with a constantly growing daisy-chain of 9-volt batteries, he had a firm grasp on the technique in no time. As you can see in the picture above, the anodizing works quite well, producing vivid colors on the titanium bands without the need for any sort of dye.
[POTUS31’s] favorite color thus far? A rich green that comes from oxidizing the metal at you guessed it – 99 volts.
What do those colorful iPod Nano cases have in common with sapphires? In both substances the color is not on the surface, but integrated in the structure of the material. As usually, [Bill Hammack] unveils the interesting concepts behind coloring metal through anodization in his latest Engineer Guy episode.
We’re not strangers to the anodization process. In fact we’ve seen it used at home to change the color of titanium camping utensils. [Bill] explains what is actually going on with the electrochemical process; touching on facts we already knew; like that the voltage range will affect the color of the annodized surface. But he goes on to explain why these surfaces are different colors and then outlines how anodized metals can be dyed. That’s right, those iPod cases are colored with dye that will not wash or scratch off.
Pores are opened when the aluminum goes through anodization. Those pores are filled with dye, then the metal is boiled in water which closes them, sealing in the color. Pretty neat!
Continue reading “How anodization is used to make pretty iPod colors”
While many people have tried their hand at anodizing aluminum at home, there are plenty who would just as soon leave it up to the professionals due to the highly concentrated sulfuric acid required for the process. [Ken] started thinking about the process and wondered if there was a way to get comparable results using chemicals that are easier to obtain and dispose of.
Through some experimentation he found that sodium bisulfate (NaHSO4), which is a sodium salt of sulfuric acid, can easily be used in its place with great results. The chemical is typically advertised in hardware and pool stores as “Aqua Chem”, and can be had at a very reasonable price. When paired with the proper DC current along with a cathode, the sodium bisulfate easily anodizes an aluminum workpiece and renders it ready for coloring with RIT, readily available cloth dye.
We were impressed with the results, and when looking at [Ken’s] test pieces, it seems that the metal dyed with sodium bisulfate has a more uniform, less streaky coloring to it. It’s also worth mentioning that [Ken] has found it is fairly easy to etch the aluminum before anodizing using a solution of sodium hydroxide, which is great for individuals who prefer a more matte finish.
If this is something that interests you, be sure to swing by his site. He has a posted nice video overview of the process that may be of some help.