Greig Huggins.
I have been reading on the list a lot about corrosion where two dissimilar
metals are in contact with each other. Being in the metal finishing
industry, thought I would add a few cents worth. Down here in OZ we are on
the second of two IVP's. When constructing the first, we heated the hangar
with an industrial propane gas heater where the combusted gas was vented

the hangar. The combusted gas produced heat, moisture, and acidic
bi-products. The moisture and acidic fumes resulted in accelerated

on the gear legs and other zinc coated components.  We stopped heating

gas and fixed the coatings, but the lesson was learnt. Many of the metal
components of the lancair are coated with electroless nickel, such as the
gear legs, and the plates that fix the undercarriage frame to the

The coating looks a bit like stainless steel, but according to lancair it

electroless nickel. A good choice in that it produces a uniform coating

over the part and does not introduce hydrogen embrittlement. The corrosion
resistance of electroless nickel is fairly good, given about a 25 micron
build. The big problem is where it contacts other metals like aluminium or
zinc. The aluminium is up one end of the galvanic series, and nickel

stainless steel ) is up the other end. This will produce corrosion at the
interface, especially in hot humid conditions. We removed all the
electroless nickel coated parts and applied an electrocoat finish over the
top. Electrocoat is an electroplated epoxy paint used on auto parts and
marine outboard motors. This effectively insulated the two metallic
surfaces. Another option is to apply an anti corrosive paste between the
faces. This is always done on yacht masts where stainless fittings

the aluminium. The paste contains barium chromate and prevents the
inter-face corrosion. Ask your local yacht supplies about it or Aircraft
Spruce may stock it for putting under stainless screws. Lancair has gone

a lot of trouble to produce an aircraft that does not corrode like all the
old ones, but if a few of the metalic bits are fine tuned as far as

go, then you will have a fizz free aeroplane. Hope this helps. Jon Wilcox.