The original poster wrote:

"I have a heavily rusted piece of what was high-strength steel in the
1800's.  I want to restore the mechanism to functioning condition.
Penalty for failure is severe and messy."

What's "high-strength steel"?  I understand that HSS is High Speed Steel and
that HSS has atoms other than
iron and carbon added to prevent/reduce loosing the temper of the tool in some
applications.  But what is
19th century high-strength steel?

I still use vinegar to remove rust from tools but I love it less.  I believe
that I have added pits to tools from prolonged
soaking.  I haven't tried any other chemical methods because vinegar is cheap,
readily available, and kitchen counter safe.
Now I pay more attention to how long the parts are in the vinegar bath.  I
haven't tried diluting vinegar but I may in the future.
I recall the Old Mill Rat writing about a rasp that had a long soak in a much
stronger acid.  When the rasp was removed
from the acid it was perforated much like a surform as I recall.

chuck

________________________________________
From: OldTools  on behalf of Mark Pfeifer

Sent: Monday, June 29, 2015 10:21 AM
To: Peter Evans
Cc: oldtools@s...
Subject: Re: [OldTools] Off Topic for People Who Know Some Metallurgy

I still use electrolysis for sensitive things (plane body, saw blade) but have
started using a 50-50 mix of white vinegar and water with great results. Faster,
cleaner, safer.

And I swear the "black stuff" comes off easier after electrolysis if I put some
of the 50-50 on the scub pad. I just make sure to blow dry with my heat gun as I
go.