ASTM E407 - #72 etchant - Titanium macroetching

[kingnero]

Hello everybody,

I'm trying to locate on-line an etchant for titanium macro-etching. I've had very good results with ASTM E407 - 72 etchant (supplied by a client), however I do not know the contents of it. I'd prefer to use this one again.
I have two common european alternatives I can buy (see below), I'd like to know which one these two resembles the most with the ASTM denomination (or perhaps is the same as?) E407 - 72.
Apparently, there is also another etchant that gives good results on Ti alpha-beta alloys: Kroll's etchant. It is also copied/pasted in the below picture for your information.

Could someone help me here please?

If the picture does not show, it's the formula for Keller's etchant, Fluonitric acid solution 3 and Kroll's etchant.

Also, links to webshops that sell these kind of things, recommended practices and/or other useful info is much appreciated!



edit: typo removed, additional info added

 

[Maui]

Be VERY careful when using these etchants since they all contain hydrofluoric acid. That acid is deadly, even in relatively low concentrations. Observe all safety precautions. Do not get any of it on your skin, or breathe in the vapors. Use an exhaust hood and proper personal safety protection.

Maui

 

[kingnero]

Thanks for the warning - yes, I've worked with it before, I assure you I will take all precautions necessary.

In the meanwhile, isn't there anybody who can link #72 to one of the three etchants above?

 

This might be a help.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[skailup]

E407 Etchant # 72 is another variant of HF + HNO3 solution.
10 ml HF
45 ml HNO3
45 ml water

You can buy individual chemicals from chemical supply and mix them in fume hood. For metallographic use, HF comes as ~48% conc and HNO3 as ~70% conc.

When dealing with HF, I recommend getting a couple tubes of HF antidote gel (calcium gluconate) nearby.

 

[kingnero]

@ ironic metallurgist, thanks for the very informative document. Saved it for future use.

@ skailup, the formula does not look correct to my (untrained) eye, should be far more water? And thanks for the heads up, we'ge got first aid kits (and a trained medical professional) in-house that should be aware of this - I'll transfer the message though, and check if he's got this and knows how to use it.

 

[skailup]

It is true that (micro)etchants for Ti alloys are quite diluted. However, the #72 makeup you asked about is listed in ASTM E407. The same recipe is also shown in ASTM E340, which is the macroetching standard. You can obtain the Standard copies at ASTM store.

 

[kingnero]

OK, thanks for the additional clarification. Much appreciated!