Here in Brazil we use a special detergent to clean up metals, based on Dodecylbenzene Sulphonic Acid, it is very effective at shining up all sorts of different metals.

I recently acquired 2 samples of 99.99% pure metallic cobalt for my element collection... They were covered in some sort of weird blackish-grey-green-brown residue...

I then dumped the 2 pieces of Co in a small container with this special dish detergent... to my surprise, this blackish residue immediatelly started to come off. After some time, I was left with very shiny pieces of Cobalt.

Did some reaction actually take place here? What reaction? Thanks in advance. As I understand, Cobalt is meant to be rather resistant to acids/corrosion in general.

  • 1
    $\begingroup$ The detergent is acid, probably dissolving cobalt oxides. $\endgroup$
    – Poutnik
    Commented Dec 6, 2023 at 5:51
  • $\begingroup$ Funny. It seemed like some sort of residue or dirt coming off of the metal. $\endgroup$ Commented Dec 6, 2023 at 20:18
  • $\begingroup$ "based on"? Typical detergents are salts of alkylbenzenesulphonic acids. I think that's the kind of being based on. Acid itself would be highly unlikely and I wouldn't call it a detergent. $\endgroup$
    – Mithoron
    Commented Dec 6, 2023 at 23:29
  • $\begingroup$ On the label of the detergent, the active ingredients listed are "dodecylbenzene sulfonic acid and glycolic acid". $\endgroup$ Commented Dec 7, 2023 at 1:41
  • $\begingroup$ These detergents are sold here as "Brilha Alumínio" - or somethink like "Aluminum Shine" in english. I've been able to clean up several types of metals with it... Like Copper, in which the result is instantaneous, Bismuth, Aluminum and of course, Cobalt. $\endgroup$ Commented Dec 7, 2023 at 1:45


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