Try a brief dunk in 50/50 bleach/water solution. That'll let you know if the alloy will rust at all, and possibly "kick start" the reaction by etching the surface.
Test your solution with a nail or scrap metal to see how quickly it works, because if you walk off and forget it you may not like the results.
Also may need damp box as Winter air is usually very dry. Put part in container with wet rag or sponge, put in warm place.
