kevin, i have had a lot of success, on heavy iron pieces, using vinegar and water. you just have to keep a daily eye on the relic to be sure that you stop the process before it removes more than you want removed. completely submerge in water with a vinegar to water ratio of a half cup vinegar to a gal. of water. use the white vinegar. if the object is heavily encrusted it may take 2 to 4 days to remove the surface covering. when you have removed all you intend, then soak the relic in a solution of 1 cup baking soda (well disolved) in a gallon of water. soak several hours to a day in this solution... then wash well with running water. if the relic has delicate engraving, or inscription on it, check it's progress "often" while it is in the vinegar solution, so as to not have any of the inscription deterioated.

eshel