Here is yet another approach. Volatile corrosion inhibitors. We've tried
them in nasty outdoor environments and they are just amazing. The only
disadvantage is life span. However in extremely nasty environments such as
Minnesota winters, they do really well and allow for extended service life.
They also have a conformal coating material as well
http://www.cortecvci.com/Products/products.php?showonly=ElectricRon