I need to etch some samples to be able to study the various phases in
the different materials. Anyone have ideas of what to use to etch
Stainless steel, austenitic and duplex
Aluminum with Si and Mg as alloying elements
Thanks in advance
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Probably the reason to use it fresh is that it contains cyanide. If it
accidentally contacts acid it could generate toxic gas and kill you.
Keep it around and you risk someone else blundering into killing
themselves. Common sense says avoid potential hazards like this.
One of the main reasons I asked was the issue of disposal, it is not very
economic to pay for disposal of small amounts of solution.
It would be better to wait until a reasonable amount had been collected.
I believe that the thiocyanate should be stable unless, as you say,
significant acid was added.
The used solution is slightly less of a risk in this respect than the stock
thiocyanate as it is buffered with alkali.
Both definitely need correct storage to prevent accidental misuse.
If this is the risk it is very different to the acidic oxidising agent
etches and polishing solutions which are inherently unstable and can not be
stored at all particularly when contaminated by metal salts after use.
That thought did cross my mind but it hardly seems to warrant alll the
comments about not storing, there are plenty of other very harmful chemicals
that get stored and give or can give off very dangerous vapours.