Etching of titanium, aluminum and stainless steel

Metallography textbook?

Michael Dahms

Try looking at

On a slightly separate issue, does anyone know why Murakami's etchant should be used fresh? The only thing I can think of is that the hydroxide would form a silicate if stored in glass.

Don't you just hate it when everyone tells you don't do that, but they don't tell you why, in that situation i normally do it just to see what happens.

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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.

Pittsburgh Pete

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.

Ferric chloride will etch stainless steel.

Jim Hawkins