[Growley bear]

I have had very good results cleaning rust from wheels, distributor housings, steering gear boxes and nuts and bolts with cold vinegar.
I recently tried a very rusty cylinder head for a four day cold vinegar soak and when I removed it to check progress I was not happy. Upon brushing part of the gasket surface with my stainless bristle brush I noticed that the metal surface seemed soft and left scratches as if it was hard clay. I pressure washed it and it can be saved but the moral of the story is that I will check my parts in vinegar much more closely and frequently. I soaked the head cold in a large covered plastic pan completely submerged and noticed a slow bubbling action during the process. Maybe a warning that the cast iron didn't like the vinegar? I have read that a by product of this process is hydrogen gas. I don't know how to test for that short of an explosion. I was always cautious with this process but am even more careful these days.

Chet