Hi JWL
I do not know the electrodes, but I will guess that the manufacturer will not give you a specification or chemical composition on them. If this is the case, then I believe that you will be overcharged for very standard electrodes. From the description, I would guess that they are probably ENi-CI electrodes. (There are welding consumable manufacturers that specialize in producing electrodes that are not sold to any specifications or without supplying any technical literature regarding their chemical composition. They are merely marketed as some "magical, supper dooper, highly secret" electrodes. Usually they are standard stuff that works rather well under most circumstances, that they now sell at a heafty mark-up. Typically the electrodes are 29-9 and Ni based cast iron rods.)
Remember, that if you are WELDING, then you are melting the base metal which will give you a hardened HAZ in the cast iron base metal, irrespective of the filler used. This is where your problem will lie, not in the weld metal.
Regards
Niekie Jooste
Fabristruct Solutions