Alex, the book I consulted recommends the same basic procedure as for treating bronze for
Bronze disease.
Make or like a container with aluminum foil, make sure there is
plenty of surface
area, use a 5% solution of a soda mix [5 parts soda mix in 95 parts water]. Soak the arrowheads, and soft scrub them. I would change the water after a couple days, but do this for about a week.
After the soak, dip the arrow heads in the highest grade rubbing alcohol for an hour to pull out the moisture, dry quickly, and seal with
REN wax or something similar.
Could you post a picture or scan of one of these, it would be helpful.
Bruce