Jack writes:
On 11/29/2015 10:56 PM, Bill wrote:

I found an old Marples morise chisel last night that looks very rusty
(it has "thick rust"-lol). I'm going to try to resurrect it with some
of that rust-remover liquid and a wire brush, from H.F., and a stack of
silicon carbide wet/dry. I'll take a before and after pic for fun, if it
works out.

For heavy rust, I always used Navel gel. Works a treat. When finished
wipe off with water, then lacquer thinner, then coat with Top-Coat type
product.

The problem is that once you clean up a badly rusted
cutting tool, you're often left with pitting near the
cutting edge which, unless lapped completely out,
will make it nigh impossible to sharpen the tool to a
good edge.