1 This practice is under the jurisdiction of ASTM Committee A01 on Steel, Last previous edition approved in as A – 99 (). Standard. Standard number, ASTM-A ; ASTM-A Title, Standard Practice for Cleaning, Descaling, and Passivation of Stainless. May 2nd, – Below is a technical summary of specification ASTM A 99 Advanced Plating Technologies is not. Gold plating is an exceptional finish for.
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Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation.
Organic contaminants are volatilized and most metal oxides q380-99 those of iron, nickel, and chromium will be reduced, resulting in a clean, oxide-free surface. 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.
Thus, passivation may refer to the chemical removal of free iron or iron compounds from z380-99 surface, or it may refer to the spontaneous development of a chemically inactive surface protective oxide film on the stainless steel. The presence of any free iron inadequate passivation is indicated by the deposition of copper on the surface where free iron is present.
Passivation results in the formation of an oxide film having a higher chromium-to-iron ratio than the underlying stainless steel because of the preferential oxidation of chromium and the preferential dissolution of iron. In order to avoid ambiguity in the setting of requirements, it may be necessary for the purchaser to define precisely the intended meaning of passivation. It was at one time considered that an oxidizing treatment was necessary to establish this passive 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.
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.
This standard covers both nitric and citric acid treatments. Active view current version of standard.
More Content by Carl R. Once the surface is cleaned and the bulk composition of the stainless steel is exposed to air or an oxygen-containing chemical environment, the passive film forms immediately. Fabricators, designers, and users of stainless steel components must understand the factors involved in successful passivation, identify the conditions under which that protective oxide film may be compromised, and use techniques that expose inadequate passivation.
Die fully sensored and still getting miss-hits? Some of the various meanings associated with the term passivation that are in common usage include the following:. Citric acid is a less hazardous method and has environmental benefits in terms of ‘NOx’ fume emission and waste acid disposal.
Meaningful tests to establish the degree of cleanness of a surface are few, and those are often difficult to administer and to evaluate objectively.
Keeping stainless steels stainless – The Fabricator
Range C Time mins. Unlike ASTM A, the standard does not require specific solutions for particular stainless steel grades or types, although 3 specific treatments are identified. Pickling, passivation and removing iron contamination with nitric acid Passivation treatments are sometimes specified, but it is important to consider whether this is strictly necessary or not.
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. Most Popular Content This Week Fabrication, additive manufacturing companies produce part for airliner Solving the skills gap one sstm at a time Top 5 in —Articles about waterjet cutting 3D scanning—The first step in making a dream come to fruition SLM Solutions white paper: When the astj was placed in service, a corrosive environment preferentially attacked the stainless steel surface under the heat tint.
A30-99 is essential that the entire surface be in a passive condition.
Keeping stainless steels stainless
Figure 2 After removal of the heat tint oxide, evidence of in-service pitting in the HAZ is apparent. While it is essential that surface contamination be removed ast, it is the latter interpretation of passivation that relates to establishing the corrosion resistance of stainless steels. The term “iron,” when hereinafter referred to as a surface contaminant, shall denote free iron.
Failure to develop and maintain this passive film renders the surface active, or possessing corrosion resistance similar to conventional steel’s or cast iron’s. The standard notes that the high carbon martensitic stainless steels, such as C, are not suitable for acid passivation as they can asrm attacked or be subject to hydrogen embrittlement.
ASTM A Passivation Standard | Able Electropolishing
Typical chemical treatment involves exposing the stainless steel surface to an oxidizing acid solution in which the significant variables are time, temperature, and concentration. Related Links Suppliers of Passivating Products.
The treatments are then defined by the ashm classes.
Specifications for passivation treatments for stainless steels Traditionally the American standards have been used. Light oxides can be removed with bright annealing when possible; light tints and iron contamination may be cleaned with citric acid solutions; darker tints may require cleaning with various pickling pastes; while heavier, darker oxide films will require pickling solutions. Stainless steel owes its corrosion resistance to its ready oxidation to form this protective film; however, stainless steel’s asfm to an oxidizing environment at higher temperatures or to a more highly oxidizing environment at a given temperature will result in the formation of an oxide heat tint of increasing thickness, ranging in color from a light straw to a dark black.
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.