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Weld Passivation

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We are designing and having built 304 stainless steel tanks. Roughly 12'w x
11' d x 70'L. The customer wants the interior welds to be passivated.  The
customer specification states:

	"All welds must be smooth with no holes, high spots, lumps, nor
pockets.  They must be free of oxide inclusions, with all weld spatter
removed and all welds ground smooth.  The discoloration etc. on the reverse
face of welds which are visible will be brushed with stainless steel
brushes.  All welds will be deoxidized after fabrication using deoxidizing
paste strictly in accordance with paste manufacturers instructions."

A different portion of the customer specification states:

	"Welds . . shall be passivated with a solution consisting of 10%
nitric acid . . Allow the solution to be on  the weld and cure for 1
minute."

I understand passivation to mean cleaning the stainless steel with an acid
in order to allow the protective passive film to form on the surface of the
stainless steel.  I also understand that it is debatable whether this is
necessary.

my questions:

1 The passivation treatment described in the customer spec is not close to
what is described in ASTM A967-99 (Spec. for passivation) which requires a
20 to 45% volume nitric acid and an immersion time of 30 minutes at 70 to 90
deg..  Is the lesser concentration (10%) and time effective?

2  What is the 'deoxidizing' treatment?  Is this a passivation treatment or
is this something that makes the nitric acid passivation unnecessary.  My
conversations with shop guys and our welding supplier indicate that this is
beyond passivation but no one is sure of the exact requirements.  Does
anyone know of a 'deoxidizing paste' supplier whom I may be able to get
literature from.

Thank you in advance,

Rich

Rich Kipke, PE
Project Engineer - Structural
Haden, inc.
1399 Pacific Drive
Auburn Hills,  MI 48326-1569
Direct: (248)-475-5144  Fax: (248)-475-5227
RKipke(--nospam--at)haden.com



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