I'm having a small problem.
Before I've used white vinegar ( contains acetic acid ) for anodising Titanium and almost got
up to the green hue ,without even etching the metal surface.
Did some searching on the web and found quite a few professional in Titanium anodising are
using oxalic acid. Dilute and cold it serves as an electrolyte for the anodisation bath ,
while in more concentrated solutions and hot it etches lightly and nicely the Titanium ,
thus making it easier to achieve the 2nd order* colors -being from yellow gold to green -
So ,Went to the local chemist store and got it .
Ain't the cheapest chemical,that's for sure.
But ...
Up till now I get really wonderful and vivid 1st order hues.
When I try for second order hues ,nope.
The surface gets really dull (looks like it is covered with thick transparent varnish )
and the 2nd order hues barely show.
-The amperage is not that high ( must not be ,it dulls the hues ).
-The electrolyte solution is very cold ,as it has to be.
-the aluminium cathode has about 1/4 more surface of the stem surface
and it sits deeper than the stem.
The set up is close to ideal .
Oxalic acid has double strength od acetic acid
( both are organic acids ,relatively safe to handle and with low toxicity).
What goes wrong or what's missing ,I can't tell ,right now ...
I really do not wish to use other electrolytes such as dangerous inorganic acids ,
like phosphoric and sulfuric acid .
Both are the most preferred acids to anodise Ti ,but both are extremely dangerous to handle and
work with.
Anyway.
Maybe I'll make a small electrolyte batch by just mixing them both and test it.
Now it's late at night.
I'll leave alchemy for next morning.
Feel a bit-but only just a bit - disappointed and really tired right now.
Cheers.
*orders are for hues ,what the octaves are for music notes)