TM 55-1520-240-23-1
1-82
CLEAN AND TREAT MAGNESIUM ALLOY PARTS (AVIM)
(Continued)
1-82
(1)
Mix 6 to 10 ounces of alkaline cleaner
(E117) to water, in a steel container,
to make 1 gallon of alkaline cleaning
solution.
(2)
Mix 10 to 20 percent, by weight, of
chromic acid (E114) to water in a lead-line
or 2S aluminum container, to make a
chromic acid solution.
(3)
Mix 15 to 25 percent, by weight, of
hydrofluoric acid (E201) to water in a
lead or rubber lined container to make a
hydrofluoric acid solution.
(4)
Mix 4 to 6 percent, by weight, of sodium
acid fluoride (E355) to water in a lead or
rubber lined container to make a sodium
acid fluoride solution.
(5)
Mix 10 to 20 percent, by weight, of
sodium dichromate (E357) and 0.1 to
0.25 percent by weight of calcium fluoride
(E90) to water, in a steel container to
make a dichromate solution.
b.
Clean and treat parts as follows:
(1)
Clean parts with cloths (E120) soaked in
naphtha (E245) or equivalent.
(2)
Immerse parts in alkaline cleaning
solution, maintained at 180º to 210ºF (82º
to 99ºC) for 5 to 15 minutes or until all
visible soil is removed.
(3)
Rinse parts thoroughly with cold water
and inspect for breaks in the water film. If
breaks occur, repeat step (2).
(4)
Immerse parts in solution of chromic acid
(E114), maintained at 165º to 210ºF
(74º to 99ºC) for 10 to 15 minutes.
Rinse parts thoroughly with cold water.
If necessary, the chromic acid solution
may be maintained at 70ºF (21ºC),
however, longer immersion times may be
necessary.
NOTE
Newly applied pretreatments can be
removed by this procedure. Very old
pretreatments may require additional
alternate immersion in solutions of
alkaline cleaner (E117) and chromic
acid (E114) for complete removal of
finish.
(5)
Immerse parts in solution of hydrofluoric
acid (E201). Immerse sheet stock for
approximately 30 seconds. Immerse all
other parts for 5 minutes. If parts contain
aluminum inserts, immerse them for 5 to
15 minutes in solution of sodium acid
fluoride (E335) instead of hydrofluoric
acid. Rinse all parts thoroughly in cold
running water.
(6)
Immerse parts in solution of sodium
dichromate (E357), maintained at 200º to
220ºF (93º to 104ºC), for approximately
30 minutes.
(7)
Rinse parts thoroughly. Dip them in hot
water to let them dry faster.
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