GORMAN-RUPP VG3B3-B, Installation, Operation And Maintenance Manual

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Nitric Acid Passivation of Stainless Steel
ES-1264 Nitric Acid Passivation of Stn Stl.doc 1 of 2
© 2012 Aqua-Aerobic Systems, Inc. 2012-09-19
Surface Preparation:
Initial cleaning of surface shall consist of a high pressure wash to
remove grease, oils, chemical deposits (except absorbed chemicals),
dirt, loose and moderately adherent scale, and other contaminants that
are not actually bonded to the metal.
Purpose:
For use after descaling by mechanical or other chemical methods as a
further treatment to remove residual particles of scale or products of
chemical action and to produce a uniform “white pickled” finish.
Alloy and Condition:
200 and 300 series, 400 series containing Cr. of 16% or more and
precipitation-hardening alloys, fully annealed only.
Procedure-Complete:
All stainless steel fabrications shall be acid cleaned per ASTM practice
A380-06 Section 6.2.11 and Table A2.1, Code D and passivated
according to specification A967-05 Section 6.1.1.5 consisting of a
blend of nitric acid and hydrofluoric acid in sufficient concentration to
provide removal of all discoloration and scale, and providing
passivation meeting the required passivation tests in ASTM A967-05.
Method of treatment shall be full immersion, and then welded. The
procedure for acid cleaning final fabrications with weld areas is
detailed below. Alternate methods of treatment for large fabrications
include swabbing and spraying.
Procedure-Weld Areas:
All stainless steel welded fabrications shall have welds and weld-joint
areas, tooling and working marks for several inches back from the
joint or contamination area, acid cleaned per ASTM practice A380-06
Section 6.3 and Table A2.1, Code D and passivated according to
specification ASTM A967-05 Section 6.1.1.5 consisting of a blend of
nitric acid and hydrofluoric acid in a concentration sufficient to
provide passivation meeting the required tests in ASTM A967-05.
Methods of treatment include swabbing, spraying, and paste/gel.
Rinsing:
Immediately after removal from the passivation solution, all
fabrications shall be thoroughly rinsed with potable water, with or
without a separate chemical treatment for neutralization of the acid
media, with the final rinse using water containing a maximum total
dissolved solids content of 200 ppm per ASTM specification A967-05
Section 7.2. Thorough drying should follow the final water rinse to
prevent any staining.
Testing/Inspection:
Fabrications should be free of paint, oil, grease, welding flux, slag,
scale, dirt, trash, metal chips and particles, and other gross
contamination, per ASTM A380-06 Section 7.2.1. The passivated
components shall exhibit a chemically clean surface and upon visual
inspection show no etching, pitting, or frosting resulting from the