¨Passivation
de l'acier inoxydable
Bonjour,
voilà ce qu'on trouve sur le manuel des compensateurs de pilonnement
de BOP sousmarins à propose des aciers Inoxydables:
ça vous
permettra de vous mettre à l'Anglais pour certains:
.... type
300, 302 303 304...type 347 is good welding grade but Type 316
(which is mobdyenum stabilized against carbide precipitation) is
desirable because of its greater corrosion resitance in the presence
of sea water. Bare stainless is not corrosion proof; in fact it may
rust quite readily if it is not properly cleaned and passivated to
build a tough chromic oxide film. It is this surface which is the
barrier to corrosion and rusting.
Passivation stailess steel pipe:
....it is
not stainless until achromic oxide film bilds on its surface. This
willl occur due to the exposure to oxygen of air.The passivation
process is intended to hasten and enhance the creation of this oxide
as well as to bild a thicker and tougher film.
The
passivation process will not be satisfactory unless the surface is
first cleaned.....
Caution:
Do not clean stainless steel with an ordinary wire brush which will
leave traces of iron on the surface.
Swabbing
with the pasivation solution will remove most loose solids. In
extreme cases a preliminary acid wash can be used for cleaning if
this wash is neutralized and rinsed away prior passivation.
Passivation is accomplished as follow:
-
Immerse , flush or swab with warm 20%-40% nitric acid for one
hour or longer.
-
Flush
surface with clean fresh water (not sea water) to remove all
traces of acid.
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