Painting/prep Magnesium

I have some small spots on the mag elevators that need a bit of
touch-up. On the Aluminum I use a bit of Alodyne solution. Clean it
well, then Alumaprep and then repeatedly wipe the area with Alodyne
solution until it's gold colored. Then wash thoroughly.

However, I don't know what to use in the case of Magnesium. Same
stuff or what? Any socially acceptable suggestions?

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger, Polyfiber sells magnedyne by the quart, which is cheap. You
prep by rubbing any powdery corrosion away with scotchbrite, then with
an alkaline solution (caustic soda), then application of the
magnedyne, which is a dilute chromic acid. Directions are on the
label.

Careful, because the chromium is hexavalent. MSDS can be found on the
web.

There are other treatments, and I suspect the alodine chromic acid
treatment for aluminum will work, except you don't use phosphoric acid
as a pre-prep.

I have seen other details on using irridite or something of the sort
you mix up in AC 43.13 and also in a Continental engine rebuild manual.
Many of the Continentals have accessory cases cast from magnesium.
It is lighter than aluminum and usually of a darker color. The last
magnesium I did was with Polyfiber's treatment and it made the metal
appear iridescent and darkened it a little. Then I painted it --- a
rear case --- with Continental gold. Whereupon it was just
scintillating. It rocked!

On 16 Oct 2005 15:15:42 -0700, wrote:

Roger, Polyfiber sells magnedyne by the quart, which is cheap. You
prep by rubbing any powdery corrosion away with scotchbrite, then with
an alkaline solution (caustic soda), then application of the
magnedyne, which is a dilute chromic acid. Directions are on the
label.

If Magnedyne is dilute Chromic Acid then it is the same as Alodyne
which is also dilute Chromic Acid. (Unless there are other additives
or the dilution is different)


Careful, because the chromium is hexavalent. MSDS can be found on the
web.

Rubber gloves and good ventilation.


There are other treatments, and I suspect the alodine chromic acid
treatment for aluminum will work, except you don't use phosphoric acid
as a pre-prep.

Considering the activity of Magnesium I'd assume the caustic soda is
pretty dilute. :-))


I have seen other details on using irridite or something of the sort

Not familiar with that.

you mix up in AC 43.13 and also in a Continental engine rebuild manual.
Many of the Continentals have accessory cases cast from magnesium.
It is lighter than aluminum and usually of a darker color. The last
magnesium I did was with Polyfiber's treatment and it made the metal
appear iridescent and darkened it a little. Then I painted it --- a
rear case --- with Continental gold. Whereupon it was just
scintillating. It rocked!

I have some spots to touch up and a lot of cleaning. The Deb was
corrosion proofed some years back and after a few hot days you can
find almost every seam.

It really needs to be stripped and steam cleaned. The only spots
showing up are along the edges of seams or rivets which indicates a
poor job of cleaning/prep on the previous paint job.
I'll probably hit the spots and seams with an air brush to fill in.

What it really needs is a good rubbing out followed by a clear coat.
Some kind soul wanted to make it look really nice before selling it
(it already looked good) and they buffed it out which took off the top
coat so as soon as the wax wears the finish gets dull.

That and I need to take it over to Deshannon and have the tip tanks
replaced and strobes added. With two 15 gal tip tanks (New ones are
17) that thing will stay up there all afternoon plus at 75% and still
have more than an hour reserve.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

In article ,
Roger wrote:

I have some small spots on the mag elevators that need a bit of
touch-up. On the Aluminum I use a bit of Alodyne solution. Clean it
well, then Alumaprep and then repeatedly wipe the area with Alodyne
solution until it's gold colored. Then wash thoroughly.

However, I don't know what to use in the case of Magnesium. Same
stuff or what? Any socially acceptable suggestions?

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Check with your paint supplier -- they usually have an excellent library
on preparations for using their paint systems with different materials.

Magnesium can be tricky, due to its affinity for the oxygen in the air.