How To Clean Zinc Alloy

Removing Tarnish

The fairy pendant pictured above has visible tarnish, causing the legs and wingtip to look a much less attractive brownish-yellow tone. This is thankfully very easy to remove - my preferred method is with common household toothpaste (non-gel varieties). To clean a component, work the paste into a lather and then apply directly to the piece, you can use a soft-bristled toothbrush or similar to get into grooves, or scrub at more stubborn tarnish (please note that sometimes, if the tarnish has been left for too long, the metal will remain  discoloured). 
Once the component is clean, rinse thoroughly to ensure there is no paste residue, then dry.

Removing Black Finish

Many zinc alloy components have a black finish in order to highlight the design and give them an antiqued look. Sometimes there can be a little too much black residue, or you may simply prefer a cleaner or brighter finish for the component.  

As long as the finish has been applied after the casting (and not the actual colour of the metal, as you will often find with the vintage bronze and copper components), this can also be removed with another common household item, nail polish remover (I use an acetone-based remover). 
If you just want to remove the excess black finish, a cotton bud dipped in the remover and wiped over the surface will usually do the trick. This tends to leave the wash in the finer grooves so that the design remains highlighted. If you'd rather try to remove all of the finish, you will likely need to immerse and soak the component completely in the nail polish remover in order to wet and thin the black finish in the finer grooves, using a soft-bristled brush to scrub.