Best Alodine

[Larry Smith]

I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
I've seen. I want a little better etch. Also it is too expensive. Who
has a better source? The old literature speaks of a powder form chromic
acid etch. Anybody know where to find it at a good price? Thanks.

[Ed Wischmeyer]

> I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
> I've seen. I want a little better etch. Also it is too expensive. Who
> has a better source? The old literature speaks of a powder form chromic
> acid etch. Anybody know where to find it at a good price? Thanks.

"Chromic acid etch" doesn't quite sound right. IIRC, chromic acid is the
alodine part, and phosphoric acid is the etch done to prepare the metal,
after surface oils are removed with a solvent.

Ed Wischmeyer

[Stealth Pilot]

On Fri, 2 Jan 2004 07:38:53 -0500, "Larry Smith"
> wrote:

>I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
>I've seen. I want a little better etch. Also it is too expensive. Who
>has a better source? The old literature speaks of a powder form chromic
>acid etch. Anybody know where to find it at a good price? Thanks.
>
the standard alodine etch is a dilute phosphoric acid.
dont know what else is in the mix to moderate its action though.
Stealth Pilot

[Orval Fairbairn]

In article >,
Stealth Pilot > wrote:

> On Fri, 2 Jan 2004 07:38:53 -0500, "Larry Smith"
> > wrote:
>
> >I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
> >I've seen. I want a little better etch. Also it is too expensive. Who
> >has a better source? The old literature speaks of a powder form chromic
> >acid etch. Anybody know where to find it at a good price? Thanks.
> >
> the standard alodine etch is a dilute phosphoric acid.
> dont know what else is in the mix to moderate its action though.
> Stealth Pilot

You can set up an alodine tank and an etch tank. The steps are:

1. Thoroughly degrease the aluminum (acetone, MEK, lacquer thinner)

2. Dip etch in a room temperature lye solution for about 3-4 minutes.
You can buy Lewis Lye at a supermarket.

3. Rinse the aluminum.

4. Dip the aluminum in a warm (120 deg F) alodine solution about 10
minutes, or until it gets a light gold color. You do NOT want it to turn
brown! Just a very light gold color is all you need.

5. Rinse the metal.

You MAY be able to get alodine powder from a plating shop -- that's
where I got some a number of years ago.

Always wear rubber (or vinyl) gloves when working with this system.

[Squirrel]

"Larry Smith" > wrote in message
...
> I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
> I've seen. I want a little better etch. Also it is too expensive.
Who
> has a better source? The old literature speaks of a powder form chromic
> acid etch. Anybody know where to find it at a good price? Thanks.


I'm a lurker in this newsgroup, but thought I could add something to this
thread.

McDermid Inc. supplies Iridite (another brand name for chromic acid). It is
available for commercial accounts only (Montreal: 514 745-7040). McDermid
has other locations in US (check the phone book or do a Google search).

From their Canada office, they sell it for $237 CDN (about $165 US) for 10
lbs. This makes 128 gallons of solution. That's a lot of chromic acid.
Issue is, how will you then dispose of it? Whatever you do, do not flush it
down the drain or dump it anywhere. Check out your municipal recycling for
hazardous waste (paint, chemicals etc). They probably will not process large
quantities for you though (considered commercial). Also, safety rules must
be followed, as this is a know carcinogenic. Now you can understand why
McDermid only sells commercially ... liability .... you should already know
something about that.

On the topic of safety, did you know that latex gloves are useless for
chromic acid? I double glove with a strong latex glove on the outside
(protects against the aluminum cleaner acid) and nitrile closest to the skin
(protects from the chromic acid). If you don't believe this, then notice the
brown chromic acid on the nitrile gloves that has just permeated through
your latex gloves. You don't want any holes or rips in your gloves.

Good linke for glove effectiveness (you can search based on chemical name):
http://www.chemrest.com/chromicacid%20ranking.htm

Before you use the chromic acid, you must properly degrease the part
(scotchbrite pads, mild detergent, etching solution, proper rinsing ... see
other responses). Dipping will give the best results (gives a nice light
gold finish, unless, of course, you use the clear/transparent version of the
chromic acid).

Once dry, finish it off by painting on a 2 part epoxy primer (Akzo Nobel).
Many other brands (mil spec) of aviation grade epoxy primers are vailable as
well. Only a very thin coating is required. Again, safety! I use a
homebrewed full ventilated mask when painting, and a rigged up paint booth
in my garage.

I buy chromic acid in gallon form (PPG DX 533 ... about $23 US) at my
automotive supply shop. I also use PPG aluminum cleaner, available in gallon
form as well for about $12 US. Found that other brands were more expensive
locally (this may vary by location). Also, I use Dawn dishwashing liquid for
degreasing parts after having used MEK to remove any manufacturing
marks/labels.

I dip all that I can (1 gallon will allow me to dip wing skins). I use
shallow cardboard boxes (Van's boxes from the tail kit is just great), and
line them with 6 mil polyethylene (construction vapour barrier). One for
etch, another for rinse, and a final one for chromic acid. Finally rinse the
part well before letting dry. Parts look really nice when dipped (did I say
that once too many?).

Beware of porous primers which require a paint to seal it off, as their main
function is to enhance adherence to the material. Most automotive primers
are porous, and will allow the metal below it to corrode. Epoxy primers tend
to not require additional sealing

Do your research and use this stuff wisely. Do net searches for other's
experiences, and finally contact the supplier for information on use and
safety.

O.T. Here's more info than you even asked for, though short and sweet :-)

Recipe for Paint booth:
Walk-in paint booth made with a couple of 2x4 hanging across the garage door
ceiling tracks. Cover all with 6 mil polyethylene. Make hole to suspend a 20
inch box fan to pressurize the booth (don't have to worry about fan igniting
flammable paint fumes since it is pushing freesh air in). Open garage door
18 inches and make a frame to fit below it. Fill the frame with paper type
furnace filters. It will catch just about all your overspray. Works for me.

Air supply for my full face respirator:
Bought a full face respirator on ebay ($40 US). Then, go to your aviation
supplier (Home Depot) and get some sump pump tubing (25 ft for about $3 US),
and a central vac wall attachment. Stop off at your local appliance repair
place and pick up a used dishwasher air blower (couldn't find any dead
dishwashers by the side of the street). The blower cost me $7 bucks. Rig
all this stuff together ... sump pump tubing to your face mask, other end to
the permanently installed central vac attachment which is connected to your
blower in another room (or outside) with more sump tubing.
Do clean that blower well before you use it, and NO, don't hook all this up
to your actual central vac plug unless you want the life sucked out of you.
I've had great success with this, and since the blower motor is not part of
the air flow as in other homemade systems (shop vac exhausts etc), you get
cool breathable air with no risk of ozone generated from sparking motors.


Disclaimer: This, of course, is done all at your own risk. It's worked for
me, it's up to you to figure out and decide if any of this information is
suitable to you.

[zxc]

hj
"Squirrel" > wrote in message e.rogers.com>...
> "Larry Smith" > wrote in message
> ...
> > I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
> > I've seen. I want a little better etch. Also it is too expensive.
> Who
> > has a better source? The old literature speaks of a powder form chromic
> > acid etch. Anybody know where to find it at a good price? Thanks.
>
>
> I'm a lurker in this newsgroup, but thought I could add something to this
> thread.
>
> McDermid Inc. supplies Iridite (another brand name for chromic acid). It is
> available for commercial accounts only (Montreal: 514 745-7040). McDermid
> has other locations in US (check the phone book or do a Google search).
>
> From their Canada office, they sell it for $237 CDN (about $165 US) for 10
> lbs. This makes 128 gallons of solution. That's a lot of chromic acid.
> Issue is, how will you then dispose of it? Whatever you do, do not flush it
> down the drain or dump it anywhere. Check out your municipal recycling for
> hazardous waste (paint, chemicals etc). They probably will not process large
> quantities for you though (considered commercial). Also, safety rules must
> be followed, as this is a know carcinogenic. Now you can understand why
> McDermid only sells commercially ... liability .... you should already know
> something about that.
>
> On the topic of safety, did you know that latex gloves are useless for
> chromic acid? I double glove with a strong latex glove on the outside
> (protects against the aluminum cleaner acid) and nitrile closest to the skin
> (protects from the chromic acid). If you don't believe this, then notice the
> brown chromic acid on the nitrile gloves that has just permeated through
> your latex gloves. You don't want any holes or rips in your gloves.
>
> Good linke for glove effectiveness (you can search based on chemical name):
> http://www.chemrest.com/chromicacid%20ranking.htm
>
> Before you use the chromic acid, you must properly degrease the part
> (scotchbrite pads, mild detergent, etching solution, proper rinsing ... see
> other responses). Dipping will give the best results (gives a nice light
> gold finish, unless, of course, you use the clear/transparent version of the
> chromic acid).
>
> Once dry, finish it off by painting on a 2 part epoxy primer (Akzo Nobel).
> Many other brands (mil spec) of aviation grade epoxy primers are vailable as
> well. Only a very thin coating is required. Again, safety! I use a
> homebrewed full ventilated mask when painting, and a rigged up paint booth
> in my garage.
>
> I buy chromic acid in gallon form (PPG DX 533 ... about $23 US) at my
> automotive supply shop. I also use PPG aluminum cleaner, available in gallon
> form as well for about $12 US. Found that other brands were more expensive
> locally (this may vary by location). Also, I use Dawn dishwashing liquid for
> degreasing parts after having used MEK to remove any manufacturing
> marks/labels.
>
> I dip all that I can (1 gallon will allow me to dip wing skins). I use
> shallow cardboard boxes (Van's boxes from the tail kit is just great), and
> line them with 6 mil polyethylene (construction vapour barrier). One for
> etch, another for rinse, and a final one for chromic acid. Finally rinse the
> part well before letting dry. Parts look really nice when dipped (did I say
> that once too many?).
>
> Beware of porous primers which require a paint to seal it off, as their main
> function is to enhance adherence to the material. Most automotive primers
> are porous, and will allow the metal below it to corrode. Epoxy primers tend
> to not require additional sealing
>
> Do your research and use this stuff wisely. Do net searches for other's
> experiences, and finally contact the supplier for information on use and
> safety.
>
> O.T. Here's more info than you even asked for, though short and sweet :-)
>
> Recipe for Paint booth:
> Walk-in paint booth made with a couple of 2x4 hanging across the garage door
> ceiling tracks. Cover all with 6 mil polyethylene. Make hole to suspend a 20
> inch box fan to pressurize the booth (don't have to worry about fan igniting
> flammable paint fumes since it is pushing freesh air in). Open garage door
> 18 inches and make a frame to fit below it. Fill the frame with paper type
> furnace filters. It will catch just about all your overspray. Works for me.
>
> Air supply for my full face respirator:
> Bought a full face respirator on ebay ($40 US). Then, go to your aviation
> supplier (Home Depot) and get some sump pump tubing (25 ft for about $3 US),
> and a central vac wall attachment. Stop off at your local appliance repair
> place and pick up a used dishwasher air blower (couldn't find any dead
> dishwashers by the side of the street). The blower cost me $7 bucks. Rig
> all this stuff together ... sump pump tubing to your face mask, other end to
> the permanently installed central vac attachment which is connected to your
> blower in another room (or outside) with more sump tubing.
> Do clean that blower well before you use it, and NO, don't hook all this up
> to your actual central vac plug unless you want the life sucked out of you.
> I've had great success with this, and since the blower motor is not part of
> the air flow as in other homemade systems (shop vac exhausts etc), you get
> cool breathable air with no risk of ozone generated from sparking motors.
>
>
> Disclaimer: This, of course, is done all at your own risk. It's worked for
> me, it's up to you to figure out and decide if any of this information is
> suitable to you.

[Larry Smith]

"Squirrel" > wrote in message
.cable.rogers.com...
>
> "Larry Smith" > wrote in message
> ...
> > I'm using DuPont's Aluminum Conversion but it doesn't work as well as
some
> > I've seen. I want a little better etch. Also it is too expensive.
> Who
> > has a better source? The old literature speaks of a powder form
chromic
> > acid etch. Anybody know where to find it at a good price? Thanks.
>
>
> I'm a lurker in this newsgroup, but thought I could add something to this
> thread.
>
> McDermid Inc. supplies Iridite (another brand name for chromic acid). It
is
> available for commercial accounts only (Montreal: 514 745-7040). McDermid
> has other locations in US (check the phone book or do a Google search).

Thanks, Squirrel, for all that most delightful information.