Hi there. I have been experimenting with anodising titanium for a little while, along with a friend. We have different set-ups, and I am following the technique outlined by Bille Seeley (SMT, TSP, etc). My friend uses sulphuric acid in place of TSP, which is something I do not want to do. His colours come out clean and pure (no mottles etc). Mine, on the other hand take forever to change, even at lower voltage, and have an effect that I can only describe as like a translucent white veil over them..
The preparation and cleaning is identical - I have prepared pieces for my friend in helping him with a collection.
Any clues?
Hi Ozzy, Firstly, it is not necessary to use sulphuric acid as your electrolyte--it is a carry over from anodizing aluminum. It actually makes no difference for the titanium.
Secondly, the veil you are seeing is likely oxide. Any time you see pastel or mottled colors instead of bright clear colors, that is oxide. This provides resistance which is why it takes forever to change color (assuming your mixing ratio of TSP is correct: Regular TSP=1 and 1/3 cups per gallon distilled water, TSP-PF= 1/2 cup per gallon distilled water).
With titanium you must remove this oxide by either chemical means (we prefer Multi Etch) or physical means. You didn't mention what grade of titanium you and your friend are using. This could also have some bearing. Grades 1-4 (Commercially pure) will always need etching first. Grades 5 & 23 (6al/4v alloy) very often don't need etching unless you are trying to hit higher voltage colors.
Just to make sure your steps are correct, here's a basic step order:
1. Clean & degrease pieces (we like heated simple green)
2. Rinse in distilled water (or Reverse Osmosis)--so you don't get mineral spots from hard water
3. Multi Etch (or physical removal)
4. Clean & degrease
5. Rinse in distilled water
6. Anodize immediately. **Note: Titanium will rebuild it's oxide layer when in contact with oxygen, so at the very least, anodize it up to 5-10 volts to "seal" the etch in. That way you can come back in a year and color up to whatever color you want without etching again.
7. Rinse in distilled water
8. We prefer blowing dry with a hair dryer vs air drying
Hope this helps!
me again. I think I give up. I have followed the steps over and over, and I get a lot of bubbles happening, but not colour higher than pale blue...then it fades.
Hi Ozzy,
Could you post a picture of the "faded" material?
If you're seeing lots of bubbling when anodizing, it means there is still resistance on the surface. This can be oxide (highly likely) or surface contamination from finishing--meaning you bead blasted/tumbled/polished using media with Aluminum or other metals. Those metals can get in the pores of the titanium which will then cause problems when you anodize. If you have a scrap piece of same lot of titanium, try deeply scratching or cutting the metal and then anodizing immediately. If where you cut/scratched is brightly colored, then you know there is oxide/contamination on the surface.
Also, remember, every lot of titanium is different and you won't know how thick the oxide layer is. If the metal has been produced at the mill and not allowed to cool properly, the oxide could actually be thick enough to produce an "alpha case" on the surface which is very difficult to remove. Where normally Multi Etch can remove oxide in 7-10 seconds, it might take 5 minutes. Other options are physically removing by tumbling in ceramic media and you can even add some Multi Etch to the tumbling.
How old is your Multi Etch? It may be spent if you've used it a lot or heated it a lot. You might want to try a new batch. Additionally, you can find more info on Multi Etch here: www.multietch.com/multietch-resources