How to remove anodization from aluminium?



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"Tho X. Bui" <[email protected]> wrote in message news:[email protected]...
>
> The active ingredient is sodium hydroxide (NaOH), also known as lye or caustic soda. This stuff
> will attack aluminum oxide very quickly, but becareful: aside from being rather nasty stuff to
> your body, soaking your aluminum part in aqeous solution of this tuff will cause hydrogen
> absorbtion and embrittlement of the aluminum alloy. Ditto with immersing it in an ultrasonic
> cleaner.
>
> Tho

Hydrogen embrittlement is a new one to me. The gas diffusion rate into a metal is far too slow to
cause serious structure change. Do you mean a surface effect, leading to corrosion?
 
Brian Lerner wrote:
>
> "Tho X. Bui" <[email protected]> wrote in message news:[email protected]...
> >
> > The active ingredient is sodium hydroxide (NaOH), also known as lye or caustic soda. This stuff
> > will attack aluminum oxide very quickly, but becareful: aside from being rather nasty stuff to
> > your body, soaking your aluminum part in aqeous solution of this tuff will cause hydrogen
> > absorbtion and embrittlement of the aluminum alloy. Ditto with immersing it in an ultrasonic
> > cleaner.
> >
> > Tho
>
> Hydrogen embrittlement is a new one to me. The gas diffusion rate into a metal is far too slow to
> cause serious structure change. Do you mean a surface effect, leading to corrosion?

The only reason hydrogen embrittlement seems slow on aluminum is because the oxide is relatively
impermeable to hydrogen, and the NaOH breaks the oxide down. The R&D work came from one of my
groupmates in the 80's and 90's. The effect will cause mechanical strength drop as well as
dimensional changes. Removal after immersion will not get rid of the effect because the hydrogen is
trapped inside the metal after the (natural) oxide reforms.

Tho
 
Any idea what the aerospace guys do after chem-milling aluminum alloys?

"Tho X. Bui" <[email protected]> wrote in message news:<[email protected]>...
> Brian Lerner wrote:
> >
> > "Tho X. Bui" <[email protected]> wrote in message news:[email protected]...
> > >
> > > The active ingredient is sodium hydroxide (NaOH), also known as lye or caustic soda. This
> > > stuff will attack aluminum oxide very quickly, but becareful: aside from being rather nasty
> > > stuff to your body, soaking your aluminum part in aqeous solution of this tuff will cause
> > > hydrogen absorbtion and embrittlement of the aluminum alloy. Ditto with immersing it in an
> > > ultrasonic cleaner.
> > >
> > > Tho
> >
> > Hydrogen embrittlement is a new one to me. The gas diffusion rate into a metal is far too slow
> > to cause serious structure change. Do you mean a surface effect, leading to corrosion?
>
> The only reason hydrogen embrittlement seems slow on aluminum is because the oxide is relatively
> impermeable to hydrogen, and the NaOH breaks the oxide down. The R&D work came from one of my
> groupmates in the 80's and 90's. The effect will cause mechanical strength drop as well as
> dimensional changes. Removal after immersion will not get rid of the effect because the hydrogen
> is trapped inside the metal after the (natural) oxide reforms.
>
> Tho
 
Yeah, that's why I was surprised. I know Boeing was chem-etching their 777 wings (my old company
sold them the chemicals).

Tho- By slow diffusion into the metal, I was referring to hydrogen actually going INTO the metal to
change the structure. Diffusion into a solid is typically 10^-12 to 10^-15 cm/s, so you really
aren't changing the internal metal structure. I'm not refuting the idea of hydrogen embrittlement,
just pointing out that it must be a surface effect.

"almost fast" <[email protected]> wrote in message
news:[email protected]...
> Any idea what the aerospace guys do after chem-milling aluminum alloys?
 
Just curious -- what chemicals are they? Got details on what it would take to make my shift pods
loose a few grams? ;-)

"Brian Lerner" <[email protected]> wrote in message
news:<[email protected]>...
> Yeah, that's why I was surprised. I know Boeing was chem-etching their 777 wings (my old company
> sold them the chemicals).
>
> Tho- By slow diffusion into the metal, I was referring to hydrogen actually going INTO the metal
> to change the structure. Diffusion into a solid is typically 10^-12 to 10^-15 cm/s, so you really
> aren't changing the internal metal structure. I'm not refuting the idea of hydrogen embrittlement,
> just pointing out that it must be a surface effect.
>
> "almost fast" <[email protected]> wrote in message
> news:[email protected]...
> > Any idea what the aerospace guys do after chem-milling aluminum alloys?
 
Brian Lerner wrote:
>
> Yeah, that's why I was surprised. I know Boeing was chem-etching their 777 wings (my old company
> sold them the chemicals).
>
> Tho- By slow diffusion into the metal, I was referring to hydrogen actually going INTO the metal
> to change the structure. Diffusion into a solid is typically 10^-12 to 10^-15 cm/s, so you really
> aren't changing the internal metal structure. I'm not refuting the idea of hydrogen embrittlement,
> just pointing out that it must be a surface effect.

I'm not in the industry so have no idea what they do. Remember also that fatigue is also a surface
effect failure; as well as that hydrogen diffuses via short-circuit paths along dislocations much
more rapidly than, say, carbon in iron. The experiments we performed in the lab usually involve
immersion in NaOH solution between 1/2 hour to hour long.

Tho
 
Right, so you're saying that the hydrogen in essence exacerbates any material defects in the
aluminum. Okay, guess that's why I'm a chemist rather than an engineer.

"Tho X. Bui" <[email protected]> wrote in message news:[email protected]...
>
>
> Brian Lerner wrote:
> >
> > Yeah, that's why I was surprised. I know Boeing was chem-etching their
777
> > wings (my old company sold them the chemicals).
> >
> > Tho- By slow diffusion into the metal, I was referring to hydrogen actually
going
> > INTO the metal to change the structure. Diffusion into a solid is
typically
> > 10^-12 to 10^-15 cm/s, so you really aren't changing the internal metal structure. I'm not
> > refuting the idea of hydrogen embrittlement, just pointing out that it must be a surface effect.
>
> I'm not in the industry so have no idea what they do. Remember also that fatigue is also a surface
> effect failure; as well as that hydrogen diffuses via short-circuit paths along dislocations much
> more rapidly than, say, carbon in iron. The experiments we performed in the lab usually involve
> immersion in NaOH solution between 1/2 hour to hour long.
>
> Tho
 
Uhhh . . . I'd like to claim trade secrets, but, honestly, I've just forgotten. If I tried to come
up with something off the top of my head, it's probably shave all of the grams off of your shifters.

I do remember a secret formulation for giving aluminum a mirror-like surface, but it's not something
you'd want to fool around with (how's that for cryptic?).

"almost fast" <[email protected]> wrote in message
news:[email protected]...
> Just curious -- what chemicals are they? Got details on what it would take to make my shift pods
> loose a few grams? ;-)
 
Hydrogen embrittlement is created when doing electrolytic plating in a acidic solution. The hydrogen
ions are generally driven out by baking is the item at 300° for a couple of hours immediately after
removal from the plating bath.
--
Cy Galley, TC - Chair, Emergency Aircraft Repair, Oshkosh

Editor, EAA Safety Programs [email protected] or [email protected]

Always looking for articles for the Experimenter

"Brian Lerner" <[email protected]> wrote in message
news:[email protected]...
> Yeah, that's why I was surprised. I know Boeing was chem-etching their
777
> wings (my old company sold them the chemicals).
>
> Tho- By slow diffusion into the metal, I was referring to hydrogen actually
going
> INTO the metal to change the structure. Diffusion into a solid is
typically
> 10^-12 to 10^-15 cm/s, so you really aren't changing the internal metal structure. I'm not
> refuting the idea of hydrogen embrittlement, just pointing out that it must be a surface effect.
>
> "almost fast" <[email protected]> wrote in message
> news:[email protected]...
> > Any idea what the aerospace guys do after chem-milling aluminum alloys?
 
On Fri, 24 Jan 2003 14:15:02 GMT, "Cy Galley" <[email protected]> wrote:

>Oven cleaner generally is basic in nature with sodium hydroxide. Drano drain cleaner is a little
>more concentrated. Just read the label. If you mix the drain cleaner with some water, be careful as
>it generates heat, even boiling and may spatter. Wear glasses and protective clothes.
>
>
IT also can produce hydrogen gas. Mr. Wizard places some aluminum foil in a coke bottle (old style
glass ) filled with drano (lye) and a balloon on top. Balloon fills and flys away. Also goes Whouff
if lit by stupid kid with match.

YMMV

Bob Denton Gulf Stream International Delray Beach, Florida www.sinkthestink.com Manufacturers of
Sink the Stink
 
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