Raytheon Beech Baron E55 - Page 572

Raytheon
Aircraft
Company
BARON
55
AND
58
SHOP MANUAL
MAGNESIUM
CORROSION
REMOVAL
a.
Strip
all
paint
from the
surface,
refer
to
the
PAINT
REMOVAL
FROM MAGNESIUM SURFACES
procedures
in
this
chapter.
b.
Mechanically
remove
corrosion
by
sanding
or
rubbing
as
necessary.
If
sanding,
use
aluminium
sandpaper.
Start
with 240
grit
and
finish with
400
grit.
c.
Inspect
the
surface
carefully
to
ensure
that sufficient material remains
to
satisfy
structural
requirements.
d.
Clean
the corrosion
removed
area
with
Methyl Propyl
Ketone
(MPK)
or
naptha.
e.
Apply
corrosion treatment
to
the
unprotected
magnesium.
MAGNESIUM
CORROSION TREATMENT
Any
bare
magnesium
component
which
will be
returned
to
service
should
be
lightly
sanded
to
remove
any
oxide
coating
and
coated with
Dow
Treatment
Number
19
formula.
The
chemical
for Dow Treatment Number
19
formula
may
be
purchased
from
a
Raytheon
Aircraft
Company
authorized
outlet in
powder
form
or
may
be
procured
focally
and
produced
as
follows:
a.
Place
approximately
3/4
gallon
of distilled
water
in
a
plastic
container which will
measure one
gallon
of
fluid. The
water
should
be
at
a
temperature
between
70"
and 90"F.
b. Add
1-1/3
oz.
of chromic acid
(H,Cr04).
c.
Add
1
oz.
of
calcium
sulfate
(CaS04)
to
the
water.
d.
Add
distilled water to
make
one
gallon
of
solution and
stir
vigorously
for
at
least
15
minutes.
e.
Brush
the
solution in and around the bare
surfaces
of the
magnesium,
keeping
the
area
wet
with the
solution
for
one
to
three
minutes
to
produce
a
brown
film. Do
not
exceed three
minutes.
f. Rinse
with cold
running
water
and
dry
by
exposure
to
hot air blast.
g.
Apply
a
liberal
coating
of
epoxy
based corrosion resistant
primer.
h.
Paint
to
desired
finish
color.
E21
SECTION
12
OeeP83~:Page
3