[Phantomium_Electricum]

I acquired two samples of metallic cobalt from China for my chemical element collection.
They are 99.99% pure electrolytic rounds/buttons supposedly used for steel making and other metalurgical purposes.

As the samples appeared to be tarnished and covered by a dark grayish substance, I used a special dishsoap,  based on this Dodecylbenzene Sulfonic Acid.
Immediately, all the gray/black stuff started coming off the surface of the cobalt and made my fingers dirty.

Both samples are now perfectly clean and the cobalt looks very shiny/lustrous.


What reaction took place here if any? Just curious, thanks in advance.

[Phantomium_Electricum]

Edit: I used the dishsoap to wash/clean the samples.

[Corribus]

Hazarding a guess here: cobalt is about where iron is on the activity series. So it is probably prone to surface oxidation or sulfidation, particularly in humid environments. You may have just polished off the surface layers of cobalt oxide/cobalt sulfide.

Be careful handling cobalt and other transition metals. Some of them (including cobalt) are toxic and/or carcinogenic, particularly their salts.

[Phantomium_Electricum]

Hazarding a guess here: cobalt is about where iron is on the activity series. So it is probably prone to surface oxidation or sulfidation, particularly in humid environments. You may have just polished off the surface layers of cobalt oxide/cobalt sulfide.

Be careful handling cobalt and other transition metals. Some of them (including cobalt) are toxic and/or carcinogenic, particularly their salts.

Great. One more question... The cobalt won't start tarnishing again, right? (As it is supposed to be as corrosion resistant as Nickel from what I've read.)