I'd use "zinc patina"--it doesn't really mean anything super shiny. Rather, it is an oxidation process.

Here are a few examples:

Zinc Patina
Zinc Patina. ... Posted by Ann-CCCC on October 27, 2000 at 13:48:26: In Reply to: Patina options for Zinc posted by Teresa on October 26, 2000 at 15:11:11: ...
www.stainedglasscanada.com/wwwboard/messages/978.html

Patina options for Zinc
Patina options for Zinc. ... Follow Ups: Re: Patina options for Zinc Lynne 23:58:32 10/27/00 (0): Zinc Patina Ann-CCCC 13:48:26 10/27/00 (0): ...
www.stainedglasscanada.com/wwwboard/messages/960.html

Duplex Systems:
... to form zinc oxides, zinc hydroxides and zinc carbonates. These zinc reaction products are known as the zinc patina. The zinc patina actually helps protect the ...
www.galvanizeit.org/publications/pt-ds-98.htm

Mecolin BV MAXPRO
... reasons require a colour other than the original silvery metallic zinc surface or the greyisch surface after the zinc patina has been gradually formed. ...
www.mecolin.nl/maxproe.html

RUST FREE DRY CARGO TRAILERS 630.369.8915
... to form zinc oxides, zinc hydroxides and zinc carbonates. These zinc reaction products are known as the zinc patina. The zinc patina actually helps protect the ...
www.rustfreetrucks.com/trailers/22014.html

RUST FREE REBAR AND MESH BETTER THAN EPOXY 630.369.8915 ... to form zinc oxides, zinc hydroxides and zinc carbonates. These zinc reaction products are known as the zinc patina. The zinc patina actually helps protect the ...
www.rustfreetrucks.com/rebar/22014.html