I imagine at a high enough temperature, alloys of lead and iron are formed. Little crystals of lead may sit within the iron, which likely doesn’t melt but might allow some lead in. Still, it’d probably be metallic lead rather than the much more bioavailable ionic (salt) form, but I still wouldn’t use it for cooking. Props to OP for testing it.
I would still clearly mark any cast iron that I used to melt metals.
how? what methods don’t just wash off?
A stamp on the cooking surface is one way I’ve commonly seen it done.
Gouge It with a steel tool.
LASERS!!!
I imagine at a high enough temperature, alloys of lead and iron are formed. Little crystals of lead may sit within the iron, which likely doesn’t melt but might allow some lead in. Still, it’d probably be metallic lead rather than the much more bioavailable ionic (salt) form, but I still wouldn’t use it for cooking. Props to OP for testing it.