A long time ago when I was a teenager first starting work in Seattle's
shipyards, an old machinist who rode Harleys told me that whenever he
got a part chromed he put it in his oven for some period of time to
keep it from getting brittle. I figure maybe he was talking about
hydrogen embrittlement, which could indeed happen in the acid chroming
bath.

I figure heating the metal would expand the lattice, allowing the (tiny)
hydrogen atoms to migrate. Presumably at least half of the ones right
near the edge would migrate right out of the part, and the remainder
would diffuse throughout the part, lowering the risk of a crack starting.

Is this what actually happens? If I soak some parts in salt/vinegar (a
real good way to remove rust from small parts) but am worried about
H embrittlement, can I bake the parts at say 350F for a couple of hours
and solve the problem?

Grant Erwin

"Grant Erwin" wrote in message
...
A long time ago when I was a teenager first starting work in Seattle's
shipyards, an old machinist who rode Harleys told me that whenever he
got a part chromed he put it in his oven for some period of time to
keep it from getting brittle. I figure maybe he was talking about
hydrogen embrittlement, which could indeed happen in the acid chroming
bath.

I figure heating the metal would expand the lattice, allowing the (tiny)
hydrogen atoms to migrate. Presumably at least half of the ones right
near the edge would migrate right out of the part, and the remainder
would diffuse throughout the part, lowering the risk of a crack starting.

Is this what actually happens? If I soak some parts in salt/vinegar (a
real good way to remove rust from small parts) but am worried about
H embrittlement, can I bake the parts at say 350F for a couple of hours
and solve the problem?

Grant Erwin

Grant,

In the salt/vinegar solution, there probably isn't enough hydrogen ions to
embrittle your parts. The embitterment effect gets worse the harder the
part is on the Rockwell scale. In the A/C finishing business, we had to
bake some of the exotics used in high stress applications for 23 hours @ 375
degrees to relieve embitterment, record the bake cycle and attach it to the
certs.

Ed Angell

Sorry about the spelling of embrittlement, I'll get my eyes checked Monday!

Ed Angell

"Grant Erwin" wrote in message
...
A long time ago when I was a teenager first starting work in Seattle's
shipyards, an old machinist who rode Harleys told me that whenever he
got a part chromed he put it in his oven for some period of time to
keep it from getting brittle. I figure maybe he was talking about
hydrogen embrittlement, which could indeed happen in the acid chroming
bath.

I figure heating the metal would expand the lattice, allowing the (tiny)
hydrogen atoms to migrate. Presumably at least half of the ones right
near the edge would migrate right out of the part, and the remainder
would diffuse throughout the part, lowering the risk of a crack starting.

Is this what actually happens? If I soak some parts in salt/vinegar (a
real good way to remove rust from small parts) but am worried about
H embrittlement, can I bake the parts at say 350F for a couple of hours
and solve the problem?

Grant Erwin

On Oct 13, 1:02 am, Grant Erwin wrote:
A long time ago when I was a teenager first starting work in Seattle's
shipyards, an old machinist who rode Harleys told me that whenever he
got a part chromed he put it in his oven for some period of time to
keep it from getting brittle. I figure maybe he was talking about
hydrogen embrittlement, which could indeed happen in the acid chroming
bath.

I figure heating the metal would expand the lattice, allowing the (tiny)
hydrogen atoms to migrate. Presumably at least half of the ones right
near the edge would migrate right out of the part, and the remainder
would diffuse throughout the part, lowering the risk of a crack starting.

Is this what actually happens? If I soak some parts in salt/vinegar (a
real good way to remove rust from small parts) but am worried about
H embrittlement, can I bake the parts at say 350F for a couple of hours
and solve the problem?

Grant Erwin

Hydrogen embrittlement is usually only a problem with high strength
steels. If you are concerned, baking them will solve the problem. It
is not so much that the metal expands as it is that the hydrogen has
higher average velocities when heated and therefore difuses faster.

Dan

On Fri, 12 Oct 2007 17:02:55 -0700, Grant Erwin
wrote:

A long time ago when I was a teenager first starting work in Seattle's
shipyards, an old machinist who rode Harleys told me that whenever he
got a part chromed he put it in his oven for some period of time to
keep it from getting brittle. I figure maybe he was talking about
hydrogen embrittlement, which could indeed happen in the acid chroming
bath.

I figure heating the metal would expand the lattice, allowing the (tiny)
hydrogen atoms to migrate. Presumably at least half of the ones right
near the edge would migrate right out of the part, and the remainder
would diffuse throughout the part, lowering the risk of a crack starting.

Is this what actually happens? If I soak some parts in salt/vinegar (a
real good way to remove rust from small parts) but am worried about
H embrittlement, can I bake the parts at say 350F for a couple of hours
and solve the problem?

Grant Erwin
Is this what happened to my caliper spring that I tried to de-rust in
salt & vinegar?
Gerry :-)}
London, Canada

According to Gerald Miller :
On Fri, 12 Oct 2007 17:02:55 -0700, Grant Erwin
wrote:

[ ... ]

Is this what actually happens? If I soak some parts in salt/vinegar (a
real good way to remove rust from small parts) but am worried about
H embrittlement, can I bake the parts at say 350F for a couple of hours
and solve the problem?

Grant Erwin
Is this what happened to my caliper spring that I tried to de-rust in
salt & vinegar?

Nope! Electrolytic corrosion. Multiple metals in contact with
each other and with the electrolyte (the salt and vinegar). One metal
has naturally a higher voltage in that solution than another, so current
keeps flowing from one to the other, and the one (the spring in this
case) is eaten away.

If you had separated the spring from the rest, and put it in a
different insulated container, it would probably have survived -- though
the baking to remove hydrogen would have been a good idea, as the
hydrogen would have made the spring more likely to fail in service.

Sorry,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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On 14 Oct 2007 04:30:06 GMT, (DoN. Nichols)
wrote:

According to Gerald Miller :


Is this what happened to my caliper spring that I tried to de-rust in
salt & vinegar?

Nope! Electrolytic corrosion. Multiple metals in contact with
each other and with the electrolyte (the salt and vinegar). One metal
has naturally a higher voltage in that solution than another, so current
keeps flowing from one to the other, and the one (the spring in this
case) is eaten away.

If you had separated the spring from the rest, and put it in a
different insulated container, it would probably have survived -- though
the baking to remove hydrogen would have been a good idea, as the
hydrogen would have made the spring more likely to fail in service.

Sorry,
DoN.
Thanks DoN. Fortunately I had a spare.
Gerry :-)}
London, Canada