Message-ID: <3E32446E.EDD7CC68@earthlink.net>
From: "Tho X. Bui" <blahx3@earthlink.net>
Newsgroups: rec.bicycles.tech
Subject: Re: How to remove anodization from aluminium?
Date: Sat, 25 Jan 2003 07:59:44 GMT

Nicholas & Domino wrote:
>
> Hi,
>  Im european, and I dont think I can buy that oven cleaner here....but
> are you serious that an oven cleaner is going to remove anodization???
> Can anyone tell me the composition of that oven cleaner so I look for
> a similar product here in spain?
> Regards and TIA,
>  Gonzalo

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

Message-ID: <3E3386BE.9334C860@earthlink.net>
From: "Tho X. Bui" <blahx3@earthlink.net>
Newsgroups: rec.bicycles.tech
Subject: Re: How to remove anodization from aluminium?
Date: Sun, 26 Jan 2003 06:55:11 GMT

Brian Lerner wrote:
>
> "Tho X. Bui" <blahx3@earthlink.net> wrote in message
> news:3E32446E.EDD7CC68@earthlink.net...
> >
> > 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

Message-ID: <3E34CEB0.4A2C09B5@earthlink.net>
From: "Tho X. Bui" <blahx3@earthlink.net>
Newsgroups: rec.bicycles.tech
Subject: Re: How to remove anodization from aluminium?
Date: Mon, 27 Jan 2003 06:15:29 GMT

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