[TheForge] pitted rust

Wed Oct 1 12:56:00 2003

http://magichammer.freeservers.com/

Click on "removing rust" on that page. I know that you don't want to remove
rust but there is a side effect to this method.
that is, the "scrap piece" described below becomes filled with just the sort
of pitting that you are looking for. I had some
10' long panels (made by Yellin) that needed to have rust removed. I made an
anode from a piece of 1/4" round, 10' long.
I wire brushed the anode to bright clean. After an overnight treatment, the
rust on the panel was neutralized, but the anode piece looked as if it had
been buried in the Louisiana swamp for 10 years. It was heavily rusted and
deeply pitted. I suggest using your test piece as the anode and cleaning
something that you have laying around your shop, old tongs, post vice, etc.
Let us know what happens.

dave m

One more technique for removing rust is Electrolytic Rust Removal. Rust can
be electrically etched off of iron or steel in a bath of mild alkali, such
as Sodium Carbonate. Connect the rusty part to the negative terminal of a
12V battery or battery charger and a scrap piece of steel or iron to the
positive terminal. Use one tablespoon of Sodium Carbonate per gallon of
water. This technique has many advantages. First, the alkaline solution is
much safer than some of the acids mentioned earlier. It is still a chemical,
so rubber gloves and splash goggles are recommended. Another advantage of
electrolytic rust removal is that it will have no effect on good metal, so
you can leave the work in the bath for a long time and not damage the metal.
There is no risk of hydrogen embrittlement nor of etching unrusted metal.

Electrolytic rust removal will leave a black oxide surface, which is the
result of a process that doesn't remove any good metal at all. The only
thing removed is loose rust and embedded oxygen. If your goal is to keep as
much of the original metal behind, this is the best technique. However, be
prepared to immediately follow this technique with one of the rust
prevention procedures, such as using Boeshield T9 or VPI Paper wrap.

----- Original Message ----- 
From: "Cameron Stoker" <[email protected]>
To: <[email protected]>
Sent: Wednesday, October 01, 2003 9:48 AM
Subject: [TheForge] pitted rust

> Hello all,
> I have a bit if a problem on a project and thought I should see what
> the collective wisdom of the forge might have to offer.
>
> I have a client who would like me to duplicate the rust finish found on
> an old piece of ~ 2" pipe.
> This guy is very picky and I've tried several textures which have been
> rejected.
> The difficulty is that this is some serious rust. I think this sample
> of pipe was buried in  the ground for many years. Its surface is
> covered with small pits maybe 3/23" average diameter and about 1/32
> deep. i.e. it's a fairly heavily pitted rusty surface. I am imagining
> the corrosion process could develop this way when grains of varying
> composition and size sand/minerals of the ground being pressed against
> the pipe.
>
> Typically when I do a rust finish, I treat the item with muriatic acid
> to remove any black forging oxide and to chemically clean the surface
> of oils/junk/etc. I then warm the metal with a small torch and sprits
> it with bleach solution. This gets a powdery red oxide almost
> instantly. I do several treatments with bleach solution, then switch to
> a saline solution and heat for several days. I've found using only the
> bleach solution will develop streaks in the patina and it can for white
> residues. The salt water keeps the patina even, and has some nice
> subtle color variations such as brown and black spots speckling the
> surface.
>
> The main fault with my 'artificial' rusting, is that it would take me
> years to develop any kind of deep pits on a surface. Someone suggested
> packing the pipe in a box of sawdust permeated with muriatic acid, but
> this seems like a fire hazard to me, and I bet it would still take
> years.
>
> My current best idea is to braze a lot of small diameter ball bearing
> balls to a set of die plates and texture the pipe in the hammer before
> the rusting.
>
> Anyone have any clever tricks for getting deep rust?
>
> Seems like there should be a way to do this electrochemically, perhaps
> using a plastic sponge/foam as an irregular electrode against the pipe.
>
> Thanks for any advice.
>
> Cameron Stoker
> [email protected]
> "May you run like a vicu�a!"
> pgp key @ http://keys.stoker.net
>