Yuan, Z., Xiao, J., Wang, C. et al. Preparation of a superamphiphobic surface on a common cast iron substrate. J Coat Technol Res 8, 773 (2011). https://doi.org/10.1007/s11998-011-9365-7

I don't have a subscription or SciHub link to pull up the underlying, but it looks like there have been folks who did electron microscopy on seasoned cast iron. (Note: more relevant and profitable to study in the context of machinery / engine design)

> Is there solid evidence that this is actually possible, as opposed to creating a layer on top of it?

I doubt that's actually what happens, but if you think of it that way, you'll end up with the right result.

"Soak into" is probably an engineering approximation converted to lay language.

What we're really talking about is surface-gap-filling.

So yes, "into" at some level of magnification. "Onto" at another.

Indeed! I was avoiding describing the surfaces at high detail .

Yes, this isn’t a mystery. There are lots of coated steel products that use the crudest of coatings that need grinder off. Unless the material is polished to a high shine it will absorb oil.

Tangential but related: Oilite:

https://en.m.wikipedia.org/wiki/Oilite

yeah oilite is a great bearing material, but it‘s not exactly „normal“ metal, but sintered bronze. In essence, you clump together bronze powder with a binder and then heat it up until the binder is gone and the powder has stuck together. What‘s left behind is kind of like a sponge, which enables impregnation with oil. Very special process and nothing to do with metal always having „pores“ or anything where oil can seep in

Wow that Wikipedia page reads like an ad.