From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Chrome and Nickel pistol refinishing
Organization: Lawrence Berkeley Laboratory

#	Hard Chrome is (if memory serves well) Chromium carbide plating.
#	It has been used for many years for hardfacing surfaces that are
#	expected to have to endure lots of wear, such as cam faces and the
#	sort.  When done properly it should last a very long time.  Another
#	nice aspect is that it can be renewed (so to speak) which ought to
#	extend the life of the weapon by quite a margin.

There are two common types of chrome plating: decorative chrome and hard chrome.
If you go down to your local plating shop, they'll assume you want decorative
chrome which is chrome over nickel over copper like on your car bumper.  The
nickel underlayer makes for a shiny surface.  Hard chrome is chrome which is
plated directly on to the substrate.  It is somewhat dull.  It can be put on 
very thick - 30 or even 50 mils thick if you want, so you can build up surfaces
with it.  It is very hard.  It is just as easy and cheap to do as decorative
chrome.  It has nothing to do with chromium carbide.

#	I think Nickel plate sucks for several reasons: It is prone to chemical
#	attack and it is soft.  It can also peel, though I do not have any
#	first hand knowledge about the so-called electroless plate.

There are two common types of nickel, electroless nickel and nickel plate
now often called "electro nickel".  Electro nickel is cheaper because the
bath doesn't wear out - you just add more nickel.  It is usually put over
a layer of copper to increase adhesion.  It has a coarse grain structure
and tends to build up at the high current density areas of the part, giving
an uneven plating thickness.  It is somewhat softer than electroless but still
hard.  The nickel itself is quite hard but if it is thin, the hardness you're
sensing may be that of the underlying copper.

Electroless is more expensive but gives finer grain structure.  You can 
put up to 4 or 5 mils of electroless nickel down.  It has a hardness of 
Rc 45-55 as laid down but afer a bake-out at 350-400 F for 3-4 hours, the 
hardness goes up to Rc 60-65.

Nickel plated guns have nickel over copper.  I believe these are subject to
attack from the usual chemical cleaners such as Hoppe's #9 and harsher 
because the nickel is thin enough or has enough microgaps in it to allow the
chemicals to attack the underlying copper plate.  But electroless and hard
chrome guns shouldn't be attacked.  That's the theory, anyway.  Me personally,
I use Breakfree on plated guns because I _know_ it can't hurt plating.  (And
I'm a big chicken.)

Many steels are subject to hydrogen embrittlement.  One excellent source
of hydrogen is plating baths.  Another is an acid bath for rust removal.
An excellent way to get rid of hydrogen is by bakeout in the 350-400 F
range.  This is often just below the draw-tempering range of the steels
which are subject to hydrogen embrittlement so it's a near thing.  However,
you can bake out in your home oven if it will hold temperature stably enough.
This is why you never want to acid dip a spring unless you bake it out
afterwards - plain high carbon steels will crack under stress shortly after you
dip them.  [That's personal experience talkin' there. 8-(]

I see your eyelids getting heavy so I'll spare you and stop here.

JHBercovitz@lbl.gov    (John Bercovitz)

From: bercov@bevsun.bev.lbl.gov (John Bercovitz)
Subject: Re: Chrome and Nickel pistol refinishing
Organization: Lawrence Berkeley Laboratory

In article <39251@mimsy.umd.edu> osan@cbnewsb.cb.att.com (Mr. X) writes:
#In article <39159@mimsy.umd.edu> bercov@bevsun.bev.lbl.gov 
#(John Bercovitz) writes:

##Electroless is more expensive but gives finer grain structure.  You can 
##put up to 4 or 5 mils of electroless nickel down.  It has a hardness of 
##Rc 45-55 as laid down but afer a bake-out at 350-400 F for 3-4 hours, the 
##hardness goes up to Rc 60-65.

#	This I find nearly impossible to believe.  Rc 60-65 is in the range
#	of some of the 'softer' High Speed tool steels, which range upwards of
#	72Rc.  Even 45-55 sounds way out of wack. [stuff deleted]

Now that you mention it, it _does_ sound high, doesn't it?  But that's what
I've heard from the various platers I've dealt with here in the Bay Area over
the past 15 or 20 years.  I've just called a plater I've never dealt with and
he confirms these figures.  Do you suppose it's local lore?  All I can think
of is that the process must result in a very favorable grain structure and that
it may actually be an alloy which is laid down.  Let us know what you find.

       JHBercovitz@lbl.gov    (John Bercovitz)