Removing Oxide Layer from Machine Tools

[engineer23]

Hi all! This forum has been very helpful to me in the past, so I thought I would post this question here.

I have what are basically machine tools that I am trying to examine in the SEM (I also use profilometry to gauge surface roughness). After use, the tools have residual Aluminum on them, which I etch away using a mixture of water and NaOH. Unfortunately, many of the tools also have a black oxide layer that is not removed by this etching process. I think formation of this layer is related to overheating. Is there any etchant that will take off the oxide layer, exposing the surface underneath for examination? I have though about acetone, but I have really no background in chemistry or etching, so any advice is much appreciated!

Thanks!

 

[Studiot]

The alkali you used will remove the aluminium residues but not the iron\ nickel \ chrome oxides.

I suggest you try either phosphoric acid or if that does not take it off, muriatic acid should do the trick.

Both are used and commercially available for preparation of metal surfaces (oxide layer removal) for painting.

Note well the precauations stated on the label.

In particular always add acid to water, not the other way round if you dilute the stuff.

go well