Your Metal Finishing Solution

Passivation

Passivation is a chemical treatment applied to stainless steel parts to provide resistance to oxidation, rusting and mild chemical attack. The Passivation process removes free iron (ferric material) from the surface of the parts that can be created during finishing operations such as milling, buffing, lapping, cutting, etc. These contaminants create potential sites for corrosion that result in premature deterioration of the component. The acids used for Passivation dissolve much of the alloyed iron on an atomic level right at the surface leaving a chromium and nickel-rich surface. It then creates the formation of a thin oxide film that protects the stainless steel from corrosion.

Advance Surface Technologies provides both Nitric and Citric Passivation treatments on Titanium and Stainless Steel alloys that adhere to QQ-P-35C, AMS-QQ-P-35A, AMS 2700C, ASTM A 967-05 and ASTM A 380-06 standards.

Passivation alone will not remove heavy adherent oxide films created from heat treatment, welding, hot-forming and other high-temperature operations. Therefore AST uses different types of pickling acids designed to remove these films prior to the Passivation of the parts.

Our extensive experience with Passivation allows us to choose and match the appropriate Passivation and pickling procedure for your needs and specific stainless steel grades.

Specifications

Nitric Acid Methods
  • Nitric 1: 20-25 v% Nitric Acid, 2.5 w% Sodium Dichromate, 120-130ºF, 20 minutes minimum
  • Nitric 2: 20-45 v% Nitric Acid, 70-90ºF, 30 minutes minimum
  • Nitric 3: 20-25 v% Nitric Acid, 120-140ºF, 20 minutes minimum
  • Nitric 4: 45-55 v% Nitric Acid, 120-130ºF, 30 minutes minimum
  • Nitric 5: Other combinations of temperature, time, and acid with or without accelerants, inhibitors or proprietary solutions capable of producing parts that pass the specified test requirements
Citric Acid Methods
  • Citric 1: 4-10 w% Citric Acid, 140-160ºF, 4 minutes minimum
  • Citric 2: 4-10 w% Citric Acid, 120-140ºF, 10 minutes minimum
  • Citric 3: 4-10 w% Citric Acid, 70-120ºF,  20 minutes minimum
  • Citric 4: Other combinations of temperature time and concentration of citric acid with or without chemicals to enhance cleaning, accelerants or inhibitors capable of producing parts that pass the specified test requirements
  • Citric 5:  Other combinations of temperature time and concentration of citric acid with or without chemicals to enhance cleaning, accelerants or inhibitors capable of producing parts that pass the specified test requirements. Immersion bath to be controlled at pH of 1.8-2.2
Testing Methods
  • Practice A—Water Immersion Test
  • Practice B—High Humidity Test
  • Practice C—Salt Spray Test
  • Practice D—Copper Sulfate Test
  • Practice E—Potassium Ferricyanide–Nitric Acid Test
  • Practice F—FreeIron Test
Passivation Types
  • Type II – 20-25 v% Nitric, 2-2.5 w% Sodium Dichromate, 120-130ºF, 20 minutes minimum
  • Type VI – 25-45 v% Nitric, 70-90ºF,   30 minutes minimum
  • Type VII – 20-25 v% Nitric, 120-150ºF, 20 minutes minimum
  • Type VIII – 45-55 v% Nitric, 120-130ºF, 30 minutes minimum
Testing Methods 4.4.1.1 – Water Immersion Test (performed at AST)
4.4.1.2 – High Humidity Test
4.4.2.1 – Salt Spray Test
4.4.2.2 – Copper Sulfate Test (performed at AST)
Passivation Types

  • Method 1- Passivation in Nitric Acid
  • Method 2- Passivation in Citric Acid
  • Type 1- 20-25 v% Nitric Acid, 2-3 w% Sodium Dichromate, 70-90ºF, 30 minutes minimum
  • Type 2- 20-25 v% Nitric Acid, 2-3 w% Sodium Dichromate, 120-130ºF, 20 minutes minimum
  • Type 3- 20-25 v% Nitric Acid, 2-3 w% Sodium Dichromate, 145-155ºF, 10 minutes minimum
  • Type 4- 38-42 v% Nitric Acid, 2-3 w% Sodium Dichromate, 70-120ºF,  30 minutes minimum
  • Type 5- 20-25 v% Nitric Acid, 2-3 w% Sodium Dichromate, 70-90ºF, 2 minutes minimum, Part anodic at 3-5 volts (not done at AST)
  • Type 6- 25-45 v% Nitric Acid 70-90ºF, 30 minutes minimum
  • Type 7- 20-25% v% Nitric Acid, 120-140ºF, 20 minutes minimum
  • Type 8- 45-55 v% Nitric Acid, 120-130ºF, 30 minutes
Testing Methods 3.2.1.1 Humidity
3.2.1.2 Water Immersion
3.2.1.3.1 Copper Sulfate
3.2.1.3.2 Salt Spray