Lye as an aluminum cleaner?

I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

Michael Horowitz wrote:
I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

Dunk it in a concentrated solution of lye, come back in a day, and you
won't see any corrosion!

OTOH, the aluminium will have totally dissolved.

Lye as a aluminium cleaner is possible, in some very few circumstances.

I'd suggest thin aluminium parts are not one.
You might find a wirebrush in a drill is a good idea.

And if they are in fact that corroded, consider if the strength has been
affected.

On 14 Oct 2006 13:25:41 GMT, Ian Stirling
wrote:

Michael Horowitz wrote:
I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

Dunk it in a concentrated solution of lye, come back in a day, and you
won't see any corrosion!

OTOH, the aluminium will have totally dissolved.

Lye as a aluminium cleaner is possible, in some very few circumstances.

I'd suggest thin aluminium parts are not one.
You might find a wirebrush in a drill is a good idea.

And if they are in fact that corroded, consider if the strength has been
affected.


I've wirebrushed 'til everything is shiny and was looking for an
inexpensive cleaner prior to alodizing; maybe it is poor economy;
someone suggested I look for the PPG line of cleaner and alodiner -
that would help keep me from wrapping myself around the axle over
which way to go. Thanks, Mike

"Michael Horowitz" wrote in message
...
I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike


I assume that this person is not a friend...

I've used Drano to remove the remains of an aluminium piston from inside an
iron cylinder (it was already bored to the max). It worked great... bye-bye
aluminium.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

Michael Horowitz wrote:
I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

It's almost against the rules of this newsgroup to make a positive
suggestion, dedicated as we are to tearing one another down, but I'll
risk it ;-)

The Right Way to clean mild surface corrosion off aluminum is to soak
it in a mild solution of phosphoric acid, and scrub it with a
scotchbrite pad. Suitable solutions are sold as tile cleaners or
"metal prep".

Personally, I wouldn't use a stainless wire brush. It's a little too
aggressive, and the deep scratches it will leave are likely places to
start a fatigue crack.

If Jasco Metal Prep (a common West Coast brand) and a scotchbrite pad
won't take off the corrosion, you've got a Dead Part, IMHO.

On 14 Oct 2006 09:19:06 -0700, "flybynightkarmarepair"
wrote:


Michael Horowitz wrote:
I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

It's almost against the rules of this newsgroup to make a positive
suggestion, dedicated as we are to tearing one another down, but I'll
risk it ;-)

The Right Way to clean mild surface corrosion off aluminum is to soak
it in a mild solution of phosphoric acid, and scrub it with a
scotchbrite pad. Suitable solutions are sold as tile cleaners or
"metal prep".

Personally, I wouldn't use a stainless wire brush. It's a little too
aggressive, and the deep scratches it will leave are likely places to
start a fatigue crack.

If Jasco Metal Prep (a common West Coast brand) and a scotchbrite pad
won't take off the corrosion, you've got a Dead Part, IMHO.


Thanks; I have a similar product I used to strip zinc off conduit for
inexpensive tubing (for welding practice); I'll give it a whirl - Mike

In article ,
Michael Horowitz wrote:

I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

Yes -- lye is used as an etch prior to alodyning. I would, however, use
a mild phosphoric acid solution first to remove the corrosion.

The aluminum should be left in the lye solution (NOT Drano, as it
contains potassium hydroxide, in addition to the sodium hydroxide) for
no more than 5 minutes -- just enough to etch the aluminum.

The handbooks recommend a sodium hydroxide solution heated to 120 F for
best results.

In article ,
Orval Fairbairn wrote:

In article ,
Michael Horowitz wrote:

I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

Yes -- lye is used as an etch prior to alodyning. I would, however, use
a mild phosphoric acid solution first to remove the corrosion.

The aluminum should be left in the lye solution (NOT Drano, as it
contains potassium hydroxide, in addition to the sodium hydroxide) for
no more than 5 minutes -- just enough to etch the aluminum.

The handbooks recommend a sodium hydroxide solution heated to 120 F for
best results.

Sorry -- I neglected to state that you have to rinse the metal
thoroughly after the lye etch, and before the alodine.

Michael Horowitz wrote:
I've taken my aileron apart and notice corrosion on the thin aluminum
parts, so I'm reading around about cleaning prior to alodining. I've
taken a stainless steel brush to the surface and removed most of the
corrosion, but it's really a PITA.

Someone suggested using lye as a cleaner. Anyone have any experience
using supermarket lye in that role? - Mike

------------------------------------------------------------------------------------------------------------

Dear Mike,

The suggestion by 'Someone' is a nice example of Conventional Wisdom,
which is always WRONG even though based on a kernal of truth.

The kernal of truth is that sodium hydroxide (ie, common lye without
any additives [meaning you can't use drain cleaner] get the stuff used
for making soap) has long been a standard in the preparation of
aluminum surfaces. Then comes a host of 'unimportant details' always
ignored by the Conventional Wisdomites, such as the exactly strength
and temperature of the solution, how many minutes (or even seconds!)
the part(s) is to be dipped, and the number & nature of the following
neutralizing rinses.

But the main fallacy here is that your primary interest is NOT
surface-prep but elimination of corrosion.

Airplane don't use much PURE aluminum. What we use are aluminum
ALLOYS. For aviation use, the most common alloying elements are
copper, magnesium and zinc, with manganese, silicon and tin being less
common.

'Corrosion' in airframes falls into two broad categories with WATER
common to both. In the first case, water reacts with the alloying
element, producing by-products with then react with the aluminum. In
the second case IMPURE water reacts with both the aluminum and its
alloying elements.

About the only time you see the first case is when the water comes from
snow. In all other caes, including rain water, due to contaminants in
the atmosphere (mostly sulphur but LOTS of otheres) the water is
sufficient impure to react directly with both the base metal and the
alloying element. (Ever heard of 'acid rain'? It's even more damaging
to airplanes than it is to forests, people, stone buildings and so
forth.)

The type of 'corrosion' we're dealing with is usually an oxide (but it
can also be a sulfide, halide and so on). To get rid of the corrosion
you need something that attacks it more vigorously than it attacks
either the aluminum OR its alloying elements. Which is why lye is a
bad, bad idea for corrosion removal. (Lye LOVES aluminum! It eats it
all up and rubs its tummy for more.)

Phosphoric Acid (as found in Coca-Cola and other soft drinks) is a
good, good, idea when it comes to cracking the code for aluminum
corrosion, since it loves the oxides more than the aluminum itself.
(Notice the can your soda-pop came in?)

Phosphoric Acid that has 'Aviation Certified' on the label costs a lot
more than Phosphoric Acid which does not.

For light corrosion, lay the brush aside and try a wad of aluminum foil
as your scrubber. Next step up is a Fine-grade non-metallic abrasive
pad. In each case, allow the acid to treat the scrubbed, abraided
surface.

For thin gauge sheetmetal, that's about as far as you can go since any
pit produced by the corrosion (or scratch resulting from your efforts
to remove it) whose depth exceeds 10% of the metal's thickness, is
grounds for rejection. (Sections of the wings of military aircraft
which must be walked upon during normal servicing are often forty to
sixty thou in thickness, not because the airplane needs that amount of
strength but because those surfaces must also serve as walk-ways.)

When the depth of the corrosion is 10% of the material's thickness,
you then estimate the AREA of the corrosion. If it covers more than
20% of the surface area, the part is usually tagged for replacement.

---------------------------------------------------------------------

Wherever two aluminum-alloy surfaces are in close contact, if water is
present it will be drawn into the gap (and there is ALWAYS a gap) by
capillary action. To prevent having our airplanes dissolve like
aspirin tablets -- even with alloys deemed 'non-corrosive' (which is
bull****) -- it is standard procedure to ALWAYS give such surfaces a
wipe of zinc chromate before assembly. Better still is to give each
component an overall spritz of zinc chromate. Yeah, it adds a tiny bit
to the cost, weight and assembly time. But you are seeing what happens
when those standard practices are ignored.

So don't use lye. Unless you know how to, when to and why. Do use
phosphoric acid, then neutralize it good with copious amounts of
BOILING HOT water (and use an oven or a heat gun to make sure all the
cracks are water-free after). THEN give it a spritz of zinc
chromate... because you CAN'T apply alodine, et al, to an assembled
structure. (Not only is it a waste of time & money, you're liable to
PROMOTE a new form of corrosion (chromate-ion growth) in the cracks
between the assembled parts.

-----------------------------------------------------------------------------

Don't shy away from making yourself a set of new ailerons from scratch.
With a corroded but otherewise undamaged aileron as your model the
task is not as difficult as it might seem.

-R.S.Hoover

PS -- There's no mystery to the alloying elements in aviation-grade
aluminum, they form the basis of their SAE nomenclature such as 2024,
6061 and 7075. The leading number indicates the PRINCIPLE alloying
element; 2 = copper, 6 = magnesium, 7 = zinc and so on... if that's
news to you, grab a copy of the ASS Co. catalog and give it a read.

With regard to corrosion, if you never took chemistry you might find it
worth your time to obtain a Periodic Table of the Elements and a good
basic text, such as Linus Paulings 'General Chemistry,' (probably out
of print). Rivet together a few coupons, do a few kitchen-table
experiments, add a bit of time and you will end up with a better
PRACTICAL knowledge of corrosion than most A&P's. You may then use
your corroded coupons to test various methods of removing that
corrosion, which is an education in itself, especially when you see
that the 'aviation-grade' chemicals (costing up to five times as much)
do no better -- and occasionally worse -- than chemicals from your
local paint store.

Naval Aviation exists -- literally! -- upon a good knowledge of
corrosion control. There are some outstanding Navy manuals written for
the average guy (or at least, the average sailor :-) taken from the
technical manuals, methods & procedures used by Grumman and Douglas
(ie, traditional builders of Naval aircraft) who can still teach Boeing
and Lockheed a trick or two when it comes to corrosion prevention and
aircraft maintenance in a corrosive environment (such as bobbing around
the ocean on one of them big grey things... I forget what you call
them... ) -- rsh (USN, retired [and Master of the Run-On Sentence])

"Orval Fairbairn" wrote in message
news
In article ,
Orval Fairbairn wrote:

In article ,
Michael Horowitz wrote:

...
Yes -- lye is used as an etch prior to alodyning. I would, however, use
a mild phosphoric acid solution first to remove the corrosion.

The aluminum should be left in the lye solution (NOT Drano, as it
contains potassium hydroxide, in addition to the sodium hydroxide) for
no more than 5 minutes -- just enough to etch the aluminum.

The handbooks recommend a sodium hydroxide solution heated to 120 F for
best results.

Sorry -- I neglected to state that you have to rinse the metal
thoroughly after the lye etch, and before the alodine.

Well, I guess you learn something every day.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.