[LMB] Fwd: Re: [OT] AKICOTL: metal cutting

Pat Mathews mathews55 at msn.com
Sun Oct 14 00:30:47 BST 2018

If stainless steel is so problematical, how is it that my tableware, which had had some scratches etc from ordinary use, cleaning, and even use for things it was not designed for, has held up for 20 years?
From: lois-bujold-bounces at lists.herald.co.uk <lois-bujold-bounces at lists.herald.co.uk> on behalf of Joel Polowin <jpolowin at hotmail.com>
Sent: Saturday, October 13, 2018 9:47 AM
To: lois-bujold at lists.herald.co.uk
Subject: Re: [LMB] Fwd: Re: [OT] AKICOTL: metal cutting

Baur <baur at chello.at> wrote:
>> I know that stainless-steel T-pins exist, though I haven't found
>> a local source.  I tried buying some on-line, but they turned out
>> to be regular plated T-pins.  (Test: deeply nick the surface,
>> then put between two sheets of toilet paper in a small dish.
>> Thoroughly wet with water, but don't immerse; it's important that
>> the setup have plenty of oxygen.  If the pin is just plated, it will
>> rust rapidly where it's nicked, staining the paper in less than
>> an hour.  Real stainless won't change visibly.)
> that is not entirely correct .. it depends on the type of stainless steel ..
> this comes from my experience in selling boating equipment .. the
> maritime envrionment with salt spary is one of the most corrosive you
> will regularily enocounter ..
> there is corrosion resistant stainless steel .. often called SAE304 or
> A2 or 1.4301 ..
> it resists rusting in a maritime environment - it might however,
> especially when its surface is not polished or becomes scratched may
> develop slight surface rust - this does nothing to detract from its
> mechanical properties, as there will only be a VERY thin layer of
> localised rust, it willo not go doen into its strucutre. a application
> of a polishing papaer usually removes that layer ..

Marcus, I'll grant that you know a lot more about stainless steel than
I do.  But in this specific case -- the pins looked exactly like the
regular pins that I already had; the metal didn't have the slightly
different appearance that I expect from stainless steel.  This was
in tap water, rather than something corrosive such as salt water.
And they rusted really quickly, and kept rusting over several days
until I stopped the experiment; it was pretty obvious that I was seeing
the electrochemical effect of a small anode (the small bit of exposed
metal under the scratch) and large cathode (the rest of the pin).
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