I have had troubles in my first experiencies anodizing Ti6Al4V. I
get a brown colour with little white spots and traces. Also, in some
areas, were formed gray small areas with the texture of iron oxide.
In other areas is possible to see some of the interference spectrum
colours, weakly.
I used some commercial batteries in series, with a total voltage of
near 16 volts. Also tried with a 30 volts printer power supply, with
more aggressive results: the surface plenty of grey spots.
With the same setup I get a good blue colour using grade 2 titanium,
then it seems that the setup is not the problem.
The Ti6Al4V piece of titanium was a second hand one. I burnt some
lathe chips and saw a intense flame that makes me think that it’s
real Ti6Al4V titanium. But also, I bought some second hand Ti6Al4V
solid bar pieces from other place, with the same results.
OK, first off titanium burns. All grades of titanium burn. You can
not tell the alloy by burning it. At 16 volts you would only reach a
purple/gold range. At 30 volts you
would continue up through dark to light blue. It is most likely a
matter of surface prep. Remove the surface of the
titanium completely. Titanium picks up everything it touches. That
includes crap from your tools. Isolate the equipment you use on
titanium from other metals. Cross contamination may have happened
before you bought it. If it is scrap it is bound to have all kinds
of
junk absorbed into the surface. Scrap is scrap. Often for a reason.
If you want good results buy good material from a reliable source.
Bill
Thank you, Bill, Deborah, Michele & Sarah
Reactive Metals Studio, Inc.
I anodize niobium just about every week and I have great success
with it, so I’m no newbie to anodizing. But titanium is a MUCH
trickier beast. It’ll get gunky and “burned” looking in situations
that will yield a beautiful glowing color on the niobium. The
fantabulously wonderful people at Reactive Metals have told me that I
really need to etch my titanium before anodizing it because titanium
is SO reactive that it oxidizes almost instantly in air, and that
natural oxide layer interferes with the pretty oxide layer that I
WANT to be there.
Here’s what they told me to do…
Etch it. Rinse well. Store the etched piece in distilled water until
you’re ready to use it. Do NOT let it hang out in air, or you’ll
just have to etch again before anodizing.
That said, I’d strongly recommend talking to the Reactive Metals
people for the final say on what’s what. I have a narrow band of
anodizing skill where I’m pretty comfortable, but they’re the folks
with the Real Answers.
-Spider (eyeing some 14ga titanium jump rings that really want to be
dark blue)
etching titanium probably is a previous and desirable step. Then,
what is a good acid solution to do it?
Salvador I use mild Hydrofluoric acid ie 5% in distilled water in a
plastic container with lid and plastic tweezers to get the piece out
quickly as it only takes a few seconds. Remember Hydrofloric acid
will attack glass.
etching titanium probably is a previous and desirable step. Then,
what is a good acid solution to do it?
Salvador I use mild Hydrofluoric acid ie 5% in distilled water
in a plastic container with lid and plastic tweezers to get the
piece out quickly as it only takes a few seconds. Remember
Hydrofloric acid will attack glass
Please be advised that if you wish to use a Hydrofluoric acid
solution of any kind that you must do research on this chemical
first. It is dangerous in every form so please do not take its use
lightly. It cannot be inhaled or touched. It is a calcium attacker
and if you should get it on your skin, it will keep on burning
through to the bone. We have not been too hot on recommending its
use over the years but struggled to find a product which was safer
for the “average” home user. We eventually found a product called
Multi Etch. It is just on to the acid side of neutral. You can check
it out here: http://reactivemetals.com/Pages/rmssup.htm#me.
Good luck!
Bill, Deborah, Michele & Sarah
Reactive Metals Studio, Inc.