Stainless steel and brass passivation is done to protect the substrate metal from corrosion attacks by introducing a protective oxide layer onto the substrate surface that is less likely to react with corrosive agents thus making it a widely used metal finishing process. It extends the life of the metal parts.

2. WHAT IS PASSIVATION?
• Passivation is a widely-used metal finishing process to prevent
corrosion
• In stainless steel, the passivation process uses nitric acid or citric acid
to remove free iron from the surface
• The chemical treatment leads to a protective oxide layer that is less
likely to chemically react with air and cause corrosion
• It resists rusting

4. WHY PASSIVATION?
Passivation is a post-fabrication best practice for newly-
machined stainless steel or brass parts and components.
Benefits include:
• Chemical film barrier against rust
• Extended life of the product
• Removal of contamination from product surface
• Reduced need for maintenance.

5. According to ASTM A967, the definition of passivation is:
“the chemical treatment of stainless steel with a mild
oxidant, such as a nitric acid solution, for the purpose of the
removal of free iron or other foreign matter.”

6. PASSIVATION LAYER ON STAINLESS STEEL

7. BRASS PASSIVATION
• Brass Components faces the white rust on
brazing and the dark discoloration due to
climatic effects
• The performance and durability depends on
the corrosion resistance of the surface
• The Brass passivation is the effective
method to achieve the same
• Examples include cartridge cases,
ammunition, fuses, mechanical
components, electrical components

8. STEPS OF PASSIVATION PROCESS
• Degreasing
• Rinsing
• Alkaline cleaning (Ridoline)
• Rinsing
• Acidic cleaning
• Rinsing
• Process Passivation (SS Nitric 1, 2, 3, 4 or Brass Type I or II)
• Rinsing
• Post treatment

10. DEGREASING
• Degreasing of parts is done using
degreasing agents
• All foreign particles, oil residues,
machining residues etc are cleaned off
the surface
• Trichloroethylene is used as
degreasing agent for both SS and
Brass parts

11. RINSING
• Rinsing of parts is done after each
step which involves chemicals
• This is necessary to keep the next
treatment baths free from
impurities
• Furthermore, it cleans the
chemical residues from entering
into next bath

12. ALKALINE CLEANING
• Alkaline cleaning is done
to neutralize and remove
all acidic impurities from
the surface
• Usually this is done using
the chemical known as
“Ridoline”

13. ACIDIC CLEANING
• Acidic cleaning of parts is done using acids including Nitric Acid & Hydrofluoric Acid

14. SS PROCESS BATH 1
ASTM A967 / QQP 35 C : Nitric 1 / Type-II
Chemicals
• HNO3 : 20-25
• Na2Cr2O7 : 2.5±0.5
Process Parameters
• Temperature : 49-54 ˚C
• Time : 20 min

15. SS PROCESS BATH 2
ASTM A967 / QQP 35 C : Nitric 2 / Type-VI
Chemicals
• HNO3 : 20-45
Process Parameters
• Temperature : 21-32 ˚C
• Time : 30 min

16. SS PROCESS BATH 3
ASTM A967 / QQP 35 C : Nitric 3 / Type-VII
Chemicals
• HNO3 : 20-25
Process Parameters
• Temperature : 49-60 ˚C
• Time : 20 min

17. SS PROCESS BATH 4
ASTM A967 / QQP 35 C : Nitric 4 / Type-VIII
Chemicals
• HNO3 : 45-55
Process Parameters
• Temperature : 49-54 ˚C
• Time : 30 min

18. BRASS PROCESS BATH 1
Def Stan 03-12/1 : Type-I
Chemicals
• H2CrO4 : 220-280 g/l
• Na2SO4 : 14-26 g/l
Process Parameters
• Temperature : 15-25 ˚C
• Time : 15-25 sec

19. BRASS PROCESS BATH 1
Def Stan 03-12/1 : Type-II
Chemicals
• H2CrO4 : 100-120 g/l
• H2SO4 : 40-50 ml/l
Process Parameters
• Temperature : 15-25 ˚C
• Time : 45-75 sec