What is Passivation?



Passivation is the overlaying of a substrate or base layer with another metal. The intent is to remove any foreign or undesirable traits and improve the corrosion resistance of the stainless steel component. Chemical passivation has as its major goal to provide a layer of protection over the base metal. It helps to guard against the elementary forces of the environment into which the component will function in. Passivation is one of the most popular forms of metal finishing along with electro (and electroless) plating and industrial powder coating.

What Is the ASTM A967 Passivation Standard?

At its basis, the intent of this specification is to ensure that metal finishing shop uses either citric or nitric passivation correctly to produce quality results. This is applicable all across the globe and replicable by any metal finishing shop. The approach involves several steps. These consist of:

  • Cleaning – an essential part of preparation for passivation, it removes surface dirt, grime and other contaminants
  • Passivation – to remove free iron and other foreign bodies and contaminants from the stainless steel involving, whenever possible, complete immersion
  • Rinsing – spray and/or immersion must be thorough
  • Drying- this must immediately follow rinsing

The standards of ASTM A967 provide specific details of the acceptable methods required for passivating stainless steel. The passivation standards listed in the ASTM document embrace a variety of potential methods and techniques. They also are very specific on such aspects as recommendations and precautions for such things as cleaning, descaling and tests. The tests the ASTM document considers valid are the following:

  • Copper sulfate testing
  • Damp Cloth Test
  • High humidity testing
  • Potassium Ferricyanide–Nitric Acid Test
  • Salt spray testing
  • Water immersion testing

The instructions for conducting such tests as well as the acceptable results are also provided.

ASTM A967: Recipe for Success in Stainless Steel Passivation

The ASTM has established certain criterion to achieve consistent product quality in the metal finishing industry. By adhering to the specifications provided them, ProPlate is capable of guaranteeing each product they produce will be as those that follow. For stainless steel passivation, the recipe for success is found in the specifications of ASTM A967.

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