I've just been refurbishing a box of assorted spokeshaves - and best
of all I've finally got a Preston quirk router !
One thing I noticed is that japanning falls off when you leave it in
the electrolysis tank. Now this isn't news, but there was a very
obvious variation between US Stanley japanning, that barely shifted
unless already damaged, English Stanley japan that came off readily in
big sheets and Preston's japan that turned to mush almost instantly.
That set me thinking - _Why_ does japan come off ? I wouldn't expect
it to be affected by the current and my tank electrolyte is cold and
has a fairly neutral pH. The only reason I could think of is that the
English Stanley japan is permeable and there's some electrolytic
effect happening underneath it that destroys the adhesion. US japan
doesn't appear to detach unless the underlying iron is already
rusting, and then only by lifting around the edges. Presumably
Connecticut japan is itself impermeable.
Any thoughts ? Anyone know the various recipes used and if they did
vary like this? I'd have thought all these japans had a pretty high
bitumen content and that makes a fair electrolytic etch resist on its
own.
PS - A "quirk router" is spokeshave look-alike that cuts narrow, deep
grooves. The cutter is a double sided affair, made from a strip of
thin sheet. The business end looks like a C shape, one side cutting
the sides of the groove and the other ploughing the bottom - like a
tiny plough plane with twin nickers. Sharpening is an interesting
exercise with a tiny diamond hone!
--
'Ph'nglui mglw'nafh Cthulhu Evesham wagn'nagl fhtagn'
Unisaw A100 wrote:
>
> Andy Dingley wrote:
> >_Why_ does japan come off ?
>
> My understanding of it, based on what I've read on the Old
> Tools (The Porch Jeff) Group is, the japanning that comes
> free didn't/doesn't have a good bond/was compromised in the
> first place.
>
> UA100
That'd be my guess.
There are two things going on during electro-stripping,
which is what you're doing. First is that material is
driven off the Anode (plus pole on the set up) into
solution and from the solution onto the Cathode (minus
pole). The other thing that happens is that hyrdogen
bubbles generate on the Anode and Oxygen bubble are
generated on the Cathode. These bubble start out very
small and grow. There are twice as many bubbles
formed on the Anode than on the Cathode since it's
H2O that's being broken down into two Hs for every
O.
On really rusted pieces, the rust can extent UNDER
what appears to be a good japaned surface. The hydrogen
bubble can therefore form UNDER the japaning and,
as the bubbles expand, lift and remove some of the
japaning.
The process is similar to something called cavitation
which "eats up" ship and water pump propellers/
impellars. It's cavitation that ultrasonic cleaning
uses.
I think modern powder coating has replaced japaning
when very durable finishes are required.
BTW - electroplating and elecro stripping are "line
of sight" If the "cathode" can't "see" the part of the
"anode" you want to remove only the hyrdogen bubble
will be doing the mechanical stripping. By placing
the "anode" in the center of the stripping tank and
several "cathodes" around it, cleaning will be
improved. Cathodes shaped like the negative of the
part being stripped will produce a more uniform
surface finish. This is because you'll get higher
current density (and more stripping) on surfaces
closest to the cathode. At low current settings,
this isn't a big deal. At high current settings it
can noticably eat up anode surfaces closest to the
cathode(s).
You can also add a little protein to the stripping solution
(powdered gelatin works pretty well, though dead flies
will also add protein) to increase the "throwing" effect.
If you really want to mechanically remove rust
from deep pits you'll need a polarity flipper. What
this does is repeatedly flip the polarity, stripping
then plating the anode. The polarity flipper should
have two adjustable functions - one that sets the
percent of time stripping (should be greater than
50%) and the other that sets the time interval
for each flip. By flipping the polarity very
quickly you get a lot of very tiny bubbles forming
and collapsing on and UNDER the rust, loosening
and then removing it.
(I use to make jewelry and plating and stripping
were just two more techniques in my knowledge
and skills set)
charlie b
Have you seen this site? It is a long sheet but it seems the
best stuff was done by Stanley and Ford automobiles:
http://www.cranialstorage.com/wood/html/japanning.html
Go through the whole sheet though... real jappaning is baked
on in incremental stages of tempertures, quite a task.
(I have not done it myself yet)
Alex