Anodizing titanium black in color

A. Anodizing titanium is outside of my league, but if I recall black anodized titanium is rare. I believe that I've read letters in the past that claimed it couldn't be done. That being said, I definitely remember one letter in the past from an advertiser on this site (I don't recall who) who did black titanium and posted pictures that looked beautiful: use the search engine to check archived letters and you should be able to locate the one I recall.
Good luck,
Jim Gorsich
Compton, California, USA

A. It is voltage dependent, the end voltage, not the beginning.
I have heard of dark blue or purple, but not black.
It is a super thin film, so is not robust enough for a ring.
James Watts
- Navarre, Florida

Dear Mr Watts, What do you mean by the end voltage? When I put a ring in the anodising bath and a bangle both for 15 mins (just to be sure) at the same voltage, the colour comes out different. The dark blue colour although very pleasant still is no match for the Black PVD. any thought on other treatment? (no rhodium as black is illegal here). how about the white titanium? this one is a big mystery. Regards, Robert Meyer - Geneva, Switzerland TiO2 is a bright white color, but from my experience in anodizing it, it typically shows up as a greyish-white. I don't think you can get it any whiter than that. Colors depend on both voltage and time exposed to current. For example the substrate will usually turn reddish before it turns that greyish-white of TiO2 phase. This is because Ti2O3 (Ti+3) will form before TiO2 (Ti+4). Smaller parts = more current density per unit volume = faster transformation rate. Robert Kinner - Toledo, Ohio

A. 1. Concerning color anodizing titanium: with proper surface preparation the color will be consistent no matter how long you treat the titanium parts (of course after certain interval when it reaches the required color), and no matter how big the part is. Many parts can be colored simultaneously in a basket with the resulting color depending only on voltage setup ( see pic attached).

2. Black titanium can be done. The level of blackness depends on initial surface preparation and on type of titanium alloy you use. The pure titanium has more dark gray black, but strong adhesion; grade 5 has dark matte black but if scratched, can have visible lines; grade 6 is the optimal for black color and durability, although we have seen very good quality of blackening on alpha titanium.

3. We have seen white titanium in our experiments, however did not expect any applications, and therefore never investigated it in full. Yes, it is somewhat off-white.
But bright silver color can be achieved by color anodizing (see #5 slot in the table of colors) or by type IV anodizing (standalone photo).

A. David,
We are not aware of any mechanical ways to blacken titanium. Our blackening method is based on proprietary electrochemical anodizing.

Anna Berkovich
Russamer Lab

Pittsburgh, Pennsylvania

A. You can anodize titanium to black colour in mixture of sulfuric and hydrochloric acid.That process produce gray or grayish black coating.Resulting oxide layer can be then dyed to black colour.sulfuric acid 350-400 gr/lit, hydrocloric acid 60-65 g/lit,temp. 40-50 °C,2-3 A / dm2 , start wit low current density, then slowly rise it to 2-3 A( according to data from one Russian webpage )

Good info on that stuff is Chinese patent CN101812715B too ( it uses different solution for anodizing - 20 to 60 parts of chemical pure potassium dichromate K2Cr207, 10 to 20 parts of chemical pure manganese sulphate MnSO4, 2 to 4 parts of industrial pure blackening solution/?/, 25 to 55 parts of industrial pure ammonium sulphate ⇦ this on eBay or Amazon [affil links] (NH4)2SO4, and 1,000 parts of distilled water )

Hope it helps and good luck!
Goran Budija
- Cervski vrh Croatia

A. Source of formula no. 1 is Russian (ex USSR) book Averjanov, E.E. Spravochnik po anodirovanio, Moscow 1988.

According to Russian book P.A. Mirzoev, A.D. Davidov Anodnie procesi elektrohimicheskoi i himicheskoi obrabotki metalov,Sankt Peterburg 2013, to obtain black coating you can use 180-200 gms sulfuric acid, 0,5 A /dm2, 60-100 V, 60 -100 °C, 120-480 minutes.

Hope it helps and good luck!