The top post seems to be missing from my thread download...

Anyhow, the title should probably read "seasoning cast iron" rather than
"seasoning equipment." In addition to the seasoning another traditional
step in working castings is to pickle the casting either by immersion in a
sulfuric acid/water bath for a short time, or by dripping the pickling
solution on the surface and allowing it to run off. This is done until the
surface scale is loosened and can be brushed or ground away. In both cases
the goal is to remove the scale, which can be harder than files, so that the
soft cast iron surface is exposed and available for machining/filing.