Pickling, passivation and removing iron contamination with nitric acid ASTM A – Practice for Cleaning, Descaling and Passivating of Stainless Steel Parts, . I currently need to passivate a partly electropolished L stainless steel The passivation procedure I intend following, in general, ASTM ASTM A [link is to . Delstar Metal Finishing maintains high standards in stainless steel passivation, meeting the ASTM A standards. ASTM A passivation standards include.

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Visual inspection; wipe tests; residual pattern; water-break test; free iron test such as water-wetting or drying; high-humidity test; and copper sulfate test. If you let this solution inside your S. Link to Active This link will always route to the current Active version of the standard.

Let us know if we can help. To my knowledge it is not possible to do a combination pickling and passivation.

Passivation of L SS per ASTM A

It’s not possible to diagnose a finishing problem or the hazards of an operation via these pages. Precision inspection shall be performed by solvent-ring test, black light inspection, atomizer test, and ferroxyl test.

These recommendations are presented as procedures for guidance when it is recognized that for a particular service it is desired to remove surface contaminants that may impair the normal corrosion resistance, or result in the later contamination of the particular stainless steel grade, or cause product contamination.

We’ve been in the metal finishing business for over 80 years. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application.

Nitric acid alone can be used to remove light surface iron contamination after which the acid facilitates the passivation of the cleaned steel surface. Although cannot see the reason obviously myself?

This ensures that the surface of the workpiece is free of scale and contaminates. Passivation often follows the process of pickling. The selection of procedures from this practice to be applied to the parts may be specified upon agreement between the supplier and the purchaser. Citric acid is a less hazardous method and has environmental benefits in terms of ‘NOx’ fume emission and waste acid disposal.

This process greatly reduces the formation rust on the surface of the workpiece. Process Class Stainless Steel Types C1 or C2 Austenitics, austenitic precipitation hardening and duplex C3 High chromium martensitics C4 Ferritics, martensitics and martensitic precipitation hardening.


Degreasing and general cleaning shall be accomplished by immersion in, swabbing with, or spraying with alkaline, emulsion, chelate, acid, solvent, or detergent cleaners or a combination of these; by vapor degreasing; by ultrasonics using various cleaners; by steam, with or without a cleaner; or by high-pressure water-jetting.

The following shall be used as the basis for cleanness acceptability: This formula should not hurt your electropolished surfaces. This practice covers the standard recommendations and precautions for cleaning, descaling, and passivating of new stainless steel parts, assemblies, equipment, and installed systems. In some cases, no more than degreasing or removal of gross contamination is necessary. Tests with acceptance criteria to demonstrate that the passivation procedures have been successful are listed in 7.

It is also quite out of date and needs to be updated. Others, such as food-handling, pharmaceutical, aerospace, and certain nuclear applications, may require extremely high levels of cleanness, including removal of all detectable residual chemical films and contaminants that are invisible to ordinary inspection methods. Citric acid passivation as an alternative to nitric acid treatments Citric acid treatments can also be considered as an alternative to nitric acid as both provide the oxidising conditions necessary for passivation.

Keystone Corporation is an industry leader in the passivation of stainless steel. For more specific safety precautions see 7. I believe you must pickle the spools with an acid which contains fluoride in some form — often a standard nitric-hydrofluoric pickling acid or pickling paste, and follow this either with electropolishing or with nitric acid passivation or citric acid passivation to the standards discussed above. Depending on the application, chemical descaling acid pickling as described in 5.

Regards, Ted Mooney, P. Related Links Suppliers of Passivating Products. It therefore in no way precludes the necessity for careful planning and judgment in the selection and implementation of such procedures. This standard covers both nitric and citric acid treatments.

It was at one time considered that an oxidizing treatment was necessary to establish this passive metal oxide film, but it is now accepted that this film will form spontaneously in an oxygen-containing environment providing that the surface has been thoroughly cleaned or descaled. Parts treated however must pass specific tests to confirm the effectiveness of the passivation, although in practice the tests are for the detection of the effects of residual iron contamination on the surface of the parts.


In the case of classes C3 and C4, a two step process is defined, with a clean water rinse between the two steps, shown in the table below.

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Usually it is best to send the spools to a metal finishing shop which is already experienced in and equipped for the process. Range C Time mins. Combining values from the two systems may result in non-conformance with the standard. Consideration shall be given passivwtion the design of parts, equipment, and systems that will require cleaning to minimize the presence of areas in which dirt, or cleaning solutions might become trapped, and to provide for effective circulation and removal of cleaning solutions.

A38 facilities are capable of handling both large and small parts. Specifications for passivation treatments for stainless steels Traditionally the American standards have been used.

Give us a call or visit our contact page to request a quote for your project today! Passivation treatments are sometimes specified, but it is important to consider whether this is strictly necessary or not. The treatments are then defined by the process classes.

Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

You do not need super quality water for these processes; DI or RO water will be fine. Precaution shall always be practiced to minimize iron contamination, in reuse of cleaning and pickling solution, in water rinsing, in circulation of cleaning solutions and rinse water, in protection of cleaned surfaces, for safety, and disposal of used solutions and water. Passivation is a process that removes exogenous iron or iron compounds from the surface of the stainless steel alloy.