Passivation

Our passivation process for stainless steel improves corrosion resistance and removes foreign particulates, leaving the surface clean without changing its appearance.

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Corrosion Resistance

We measure the chrome to iron ratio (Cr/Fe) to meet quantifiable standards for optimal corrosion resistance. Passivation removes free iron and iron oxide from the stainless steel surface, leaving surface chromium for improved corrosion resistance.

Benefits of Passivation

Improves corrosion resistance without plating
Produces superior surface cleanliness
Eliminates iron contamination reactions with other materials
No rust discoloration
No dimensional change
Repairs damage to the natural chromium oxide layer

Commitment and Certifications, Not Just Promises

We maintain numerous certifications and cleaning specifications for metal passivation and cleaning processes. Certification includes the passivation of stainless steel.

We complete all stainless passivation services and testing in-house. Our passivation certifications include, but are not limited to:

AMS 2700
ASTM A967
ASTM B912
ASTM B849
MIL-STD-753B
MIL-STD-753C
ASTM F86
AMS-QQ-P-35
ASTM A380
CGA G-4.1
MIL-STD-808A
ASTM B117
MIL-F-14072D
MIL-STD-171D
WS19168A

FAQs

Passivation is a widely-used metal finishing process to prevent corrosion. With 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.

The passivation process includes but is not limited to these types of SST: 303, 304, and 316 alloys. It is typically performed to ASTM A9367 and similar industry specifications for chemical passivation.

Nitric acid passivation is the most common process, as this strong mineral acid quickly dissolves all iron compounds and other trace minerals from the stainless steel’s surface, and serves as a potent oxidizer, which helps to generate the oxide layer simultaneously.
Passivating stainless steel with citric acid is an alternate option. Citric acid is not as corrosive as nitric acid, though still powerful enough to remove free iron, etc.

Passivation Specifications
Common Specifications						Test Methods Arrow Offers
ASTM A967/A967M-17 (NITRIC ACID)	6.1.1.1 Nitric 1—The solution shall contain 20 to 25 volume percent of nitric acid and 2.5 6 0.5 weight percent of sodium dichromate dihydrate. The parts shall be immersed for a minimum of 20 min at a temperature in the range from 50 to 55°C [120 to 130°F]	6.1.1.2 Nitric 2—The solution shall contain 20 to 45 volume percent of nitric acid. The parts shall be immersed for a minimum of 30 min at a temperature in the range from 20 to 30°C [70 to 90°F]	6.1.1.3 Nitric 3—The solution shall contain 20 to 25 volume percent of nitric acid. The parts shall be immersed for a minimum of 20 min at a temperature in the range from 50 to 60°C [120 to 140°F]	6.1.1.5 Nitric 5—Other combinations of temperature, time, and concentration of nitric acid, with or without other chemicals, including accelerants, inhibitors, or proprietary solutions, capable of producing parts that pass the specified test requirements		13.3.1 Practice A—Water Immersion Test 13.3.2 Practice B—High Humidity Test (see 14.2), 13.3.3 Practice C—Salt Spray Test (see 14.3), 13.3.4 Practice D—C
ASTM A967/A967M-17 (CITRIC ACID)	7.1.1.1 Citric 1—The solution shall contain 4 to 10 weight percent of citric acid. The parts shall be immersed for a minimum of 4 min at a temperature in the range from 60 to 70°C [140 to 160°F]	7.1.1.2 Citric 2—The solution shall contain 4 to 10 weight percent of citric acid. The parts shall be immersed for a minimum of 10 min at a temperature in the range from 50 to 60°C [120 to 140°F]	7.1.1.3 Citric 3—The solution shall contain 4 to 10 weight percent of citric acid. The parts shall be immersed for a minimum of 20 min at a temperature in the range from 20 to 50°C [70 to 120°F]	7.1.1.4 Citric 4—Other combinations of temperature, time, and concentration of citric acid, with or without other chemicals to enhance cleaning, including accelerants, inhibitors, or proprietary solutions, capable of producing parts that pass the specified test requirements	7.1.1.5 Citric 5—Other combinations of temperature, time, and concentration of citric acid, with or without other chemicals to enhance cleaning, including accelerants, inhibitors, or proprietary solutions, capable of producing parts that pass the specified test requirements. Immersion bath to be controlled at a pH of 1.8 to 2.2.	13.3.1 Practice A—Water Immersion Test 13.3.2 Practice B—High Humidity Test (see 14.2), 13.3.3 Practice C—Salt Spray Test (see 14.3), 13.3.4 Practice D—Copper Sulfate Test (see 14.4)
AMS 2700 Rev F, Method 1 (NITRIC ACID)	Type 1- Low Temperature Nitric Acid with Sodium Dichromate. Bath Composition is 20 to 25% by volume of HNO3 2 to 3% by weight Na2Cr2O7·2H2O, Bath Temp 70 to 90 °F (21 to 32 °C), Immersion Time 30 minutes minimum	Type 2- Medium Temperature Nitric Acid with Sodium Dichromate. Bath Composition 20 to 25% by volume of HNO3 2 to 3% by weight Na2Cr2O7·2H2O, Bath Temp 120 to 130 °F (49 to 54 °C), Immersion Time of 20 minutes minimum	Type 3- High Temperature Nitric Acid with Sodium Dichromate. Bath Composition 20 to 25% by volume of HNO3 2 to 3% by weight Na2Cr2O7·2H2O, Bath Temp 145 to 155 °F (63 to 68 °C), Immersion Time of 10 minutes minimum	Type 6- Low Temperature Nitric Acid. Bath Composition 25 to 45% by volume HNO3, Bath Temp 70 to 90 °F (21 to 32 °C), Immersion Time of 20 minutes minimum	Type 7- Medium Temperature Nitric Acid. Bath Composition 20 to 25% by volume HNO, Bath Temp 120 to 140 °F (49 to 60 °C), Immersion Time of 20 minutes minimum	Copper Sulfate, Water Immersion, High Humidity and Salt spray test
AMS 2700 Rev F, Method 2 (CITRIC ACID)	Bath Composition - Parts shall be immersed in an aqueous solution of 4 to 10 weight percent citric acid, with additional wetting agents and inhibitors as applicable. Operating conditions - Bath temperature shall be 70 to 160 °F (21 to 71 °C) with an immersion time of not less than 4 minutes for baths operating over 140 °F (60 °C), not less than 10 minutes for baths operating in the 120 to 140 °F (49 to 60 °C) range, not less than 20 minutes for baths operating in the range of 100 to 119 °F (38 to 48 °C) or not less than 30 minutes for baths operating below 100 °F (38 °C).					Copper Sulfate, Water Immersion, High Humidity and Salt spray test
ASTM F86-21	6.2.2 Immerse in a 20 to 45 volume % nitric acid solution, at a temperature range from 20 to 30 °C [70 to 90 °F], for a minimum of 30 min. This passivation treatment is equivalent to the Nitric 2 treatment in Specification A967/A967M.	6.2.3 For an accelerated process, a 20 to 25 volume % nitric acid solution, heated at a temperature range from 50 to 60 °C [120 to 140 °F], may be used for a minimum of 20 min. This passivation treatment is equivalent to the Nitric 3 treatment in Specification A967/A967M	6.2.4 Other combinations of temperature and time using nitric acid, with or without other chemical additives, may be viable as well.			13.3.1 Practice A—Water Immersion Test (see 14.1), 13.3.2 Practice B—High Humidity Test (see 14.2), 13.3.3 Practice C—Salt Spray Test (see 14.3), 13.3.4 Practice D—Copper Sulfate Test (see 14.4) per ASTM A967/17
QQ-P-35 Rev C	Type II solution shall contain 20-25 percent by volume of nitric acid in acordance with O-N-350 and 2.5 +/- 0.5 percent by weight of sodium dichromate in accordance with O-S-595. Pars shall be processed for 20 minutes at a temperature range between 120-130F (49-54C)	Type VI solution shall contain 25-45 percent by volume of nitric acid (HNO3) in accordance with O-N-350. Parts shall be processed for 30 minutes at a temperature range between 70-90F (21-32C)				Copper Sulfate, Water Immersion, High Humidity and Salt spray test