is there such a thing as a waterproof sword/blade?

[Jim McDougall]

Originally Posted by fernando

These were mentioned in Portuguese inventories of the XVI century as ESPADAS PRETAS DE BORDO which, in a free translation, would mean BLACK SWORDS FROM ABOARD, referring to maritime crab ( colhonas) swords.

Good reference Fernando, and as Rick has noted, the painting or varnishing black was typically termed 'Japanning' , probably for the Shakudo (I believe is the term) style describing this process of protective or decorative application. This was not only used on maritime weapons, but it is known that in the Scottish Highlands, the trusty baskethilts were usually japanned black to withstand the damp climate. In Europe I believe many weapons were 'russetted' brown, for the same effect.

I do not think these treatments would apply to the blades however, as these were supposedly to be maintained with sharpening and oiling. The blueing on blades was of course a decorative treatment for officers swordblades and other weapons and as far as I know offered no protection from moisture.