Cortec VpCI-373 is the corrosion inhibitor that is recommended by Zenith.  It is a very nice product to use, as it is non-toxic and goes on just like PVA Glue (the white wood glue that comes in bottles).  Apply with a brush or small sponge just before final assembly and the Cortec will forever prevent any vapor or particles entering into the small gaps between your riveted parts.  Keeps out microscopic salts and other corrosive airborne particulates.

Unfortunately, it is insanely expensive and the smallest unit size is a 19 Liter drum.  I pay $980 for the drum, and this 19L drum is in concentrate form so it’s enough to build about 30 aircraft.  You definitely don’t need much.  Probably about 2 Liters is all you need.

I supply your Cortec in ready-to-use format with instructions and a Safety Data Sheet.  You are paying for 1 Litre and the price includes postage within Australia.