I have heard that hydrochloric acid (muriatic acid) will remove chrome and any base layer of copper. I don't know what strength is needed, though. In the UK, it is sold (low stength) as brick cleaner for removing mortar smears.
If it eats chrome and copper, it will no doubt eat into the brass as well, but I don't suppose you will mind losing a bit if it is for castings.
An idea which might work: simply put the chromed items in your crucible and heat it up. Brass melts at around 900-950C. Chromium melts at 1857C, and is slightly denser than brass, so would remain solid and sink to the bottom, with a bit of assistance to flatten it down. Then pour off the brass.
Andy