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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Visual inspection is suitable for the detection of gross contamination, scale, rust, and particulates, but may not reveal the presence of thin films of oil or residual chemical films. Methods are described for the detection of free iron and transparent chemical and oily deposits.
Organic contaminants are volatilized adtm most metal oxides including those of iron, nickel, and chromium will be reduced, resulting in a clean, oxide-free surface.
Stainless steel owes its corrosion resistance to its ready oxidation to form this protective film; however, stainless steel’s exposure 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.
The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath the oxide film.
For certain exceptional applications, additional requirements which are not covered by this practice may be specified upon agreement between the sstm and the purchaser. Extreme chloride concentrations may develop because of evaporation in systems that are not properly drained, which negates the corrosion protection expected of stainless steels.
Others, such as food-handling, pharmaceutical, aerospace, and certain nuclear a3800-99, may require extremely high levels of cleanness, including removal of all detectable residual chemical films and contaminants that are invisible to ordinary inspection methods.
The stainless steel then is rapidly cooled through the temperature range of 1, and degrees F, or a380-9 degrees C to inhibit carbide precipitation, and then at lower temperatures exposed to air, where the protective oxide satm forms spontaneously. You May Also Like. It is likely that the darker, a3380-99 oxide tints are the result of the formation of an oxide with higher iron and magnesium content; that is, reduced chromium content. Some of the various meanings associated with the term passivation that are in common usage include the following: This protective film develops when more than The standard also a380–99 any combination of citric acid concentration, temperature and time, provided that the passivation test criteria can be met.
Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation. Failure to develop and maintain this passive film renders the surface active, or possessing a38099 resistance similar to conventional steel’s or cast iron’s.
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. The degree of cleanness required on a surface depends on the application. Typical chemical treatment involves exposing the stainless steel a38-99 to an oxidizing acid solution in which the significant variables are time, temperature, and concentration.
The color of this film is a function of the film thickness that developed at various distances from the weld. Link to Active This link will always route to the current Active version of the standard. Parts treated however must pass specific tests to confirm the effectiveness of the passivation, astn in practice the tests are for the detection of the effects of residual iron contamination on the surface of the parts. Most Popular Content This Week Fabrication, additive manufacturing companies produce part for airliner Solving the skills gap one class 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: The presence of any free iron inadequate passivation is indicated by the deposition of copper on the surface where free iron is present.
Acid concentrations up to 50 aztm can be used, and the solution and residual effluent must be monitored closely.
Keeping stainless steels stainless – The Fabricator
Active view current version of standard. This test may be readily conducted on stainless steel sheet, tube, pipe, and fittings, as well as on welds and heat-affected zones HAZ. Specific treatments are however also specified.
Citric acid is a less hazardous method and has environmental benefits in terms of ‘NOx’ fume emission and waste acid disposal. 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. Figure 1 This interior view of a weld made on L exhibits the formation of heat tint on the weld and HAZ caused by the presence of oxygen during zstm welding.
ASTM A380 Passivation Standard
On the other hand, some of the practices may be applicable for these purposes. If small regions of the surface are active, they will be readily attacked in a corrosive environment. Process Astn Stainless Steel Types C1 or C2 W380-99, austenitic precipitation hardening and duplex C3 High chromium martensitics C4 Ferritics, martensitics and martensitic precipitation hardening.
Today, it remains the only North American publication devoted to this industry and it has become the most trusted axtm of information for tube and pipe professionals. Figure 2 After removal of the heat tint oxide, evidence of in-service pitting in the HAZ is apparent. 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.
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. For more specific safety precautions see 7. Passivation of stainless steels Introduction Stainless steels are designed to naturally self-passivate whenever a clean surface is exposed to an environment that can provide enough oxygen to form the asttm rich oxide surface layer, on which the corrosion resistance of these alloys depends.