Snippet from some site called TitaniumKay....
Quote:
Choosing Your Tungsten Carbide Wedding Band Ring
Make sure you ask your jeweler which metal was used in the finishing or binding process. Many manufacturers of tungsten carbide wedding band rings use cobalt as a binder, mostly because it is cheaper to produce. The problem with cobalt is that it bonds with oils in the skin and leeches out of the ring resulting in oxidation. The oxidation appears similar to tarnished silver, but cannot be removed by polishing or grinding. The better choice is nickel-binder tungsten carbide which is chemically inert, will not oxidize and because it is hypoallergenic, there is no danger of irritation to the skin. Be careful about dealing with a jeweler that doesn't specify that their tungsten wedding bands are made with the nickel binder alloy. Many jewelry stores do not know which alloy they are selling, and if they don't know, it is most likely cobalt alloy or pure tungsten, which lacks the hardness of tungsten carbide and are easily scratched.
Because of tungsten carbide's extreme hardness, wedding bands made from this metal cannot be sized like gold, silver or platinum rings. When you are ready to purchase, make sure that you take extra care in determining the proper size. In regards to engraving a tungsten carbide ring, it is possible, but the results will be very faint and difficult to read unless laser equipment is used.