On Feb 2, 3:18*am, Stealth Pilot
wrote:
...

hydrogen bubbles through a casting make it more brittle.

No.

they
significantly reduce the impact strength which is useful when you want
to smash it up for a retry at a melt.

Yes. They make the casting weaker, not more brittle.

Hydrogen embrittlement is also a potential problem with
electrolytic derusting and the the metal isn't even heated.

Hydrogen readily diffuses into cold steel. A bare steel
cylinder will not hold hydrogen for long under high pressure.
Hydrogen cylinders are plated on the inside with nickel.

...
a hydrogen bubbled casting is seldom porous though.it is porous in the
sense that it has voids through it but they arent continuous. if it is
cup shaped you can fill one with water and it wont leak.
as long as we understand what we intend by the words then a little
error in semantics here or there is of no importance.
...

Hydrogen bubbles in a casting won't do anything that other
gas bubbles in a casting do. The only reason you don't
get oxygen bubble in aluminum castings is because the
oxygen reacts with the aluminum. You can get oxygen
bubbles in copper castings, they do the same thing to
copper castings that hydrogen bubbles do to aluminum
castings but that is not called oxygen embrittlement
for the same reason that hydrogen bubbles in aluminum
castings are not called hydrogen embrittlement.

The right words convey the right idea. The wrong words
convey a wrong idea. Harsh words are unnecessary.

The whole point to a newsgroup is to exchange knowledge.

--

FF