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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Passivation treatments are sometimes specified, but it is important to consider whether this is strictly necessary or not. Unlike ASTM A, the standard does not require specific solutions for particular stainless steel grades or types, although 3 specific treatments are identified.
Link to Active This link will always route to the current Active version of the standard. 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 chromium rich oxide surface layer, on which the corrosion resistance of these alloys depends.
The presence of any free iron inadequate w380-99 is indicated by the deposition of copper on aetm surface where free iron is present. The degree of cleanness required on a surface depends on the application. It is essential that the entire surface be in a passive condition. The standard also allows any combination of citric acid concentration, temperature and time, provided that the passivation test criteria can be met.
It therefore in no way precludes the necessity for careful planning and judgment in the selection and implementation of such procedures.
Specific treatments are however also specified. The color of x380-99 film is a function of the film thickness that developed at various distances from the weld.
For more specific safety precautions see 7.
Evidence of in-service pitting in the heat tint in the HAZ may be seen in Figure 2. Pickling, passivation and removing astk contamination with nitric acid Passivation treatments are sometimes specified, but it is important to consider whether this is strictly necessary or not. The most commonly used of these is the copper sulfate test, in which a sulfuric acid-copper sulfate solution is swabbed on the surface for six minutes.
On the other hand, some of the practices may be applicable for these purposes. The author would like to thank Monty B. The standard notes that the high carbon martensitic stainless steels, such as C, are not suitable for acid passivation as they can be attacked or be subject to hydrogen embrittlement. Naturally occurring conditions such air or aerated water will do this and so under many exposure conditions stainless steels will naturally self-passivate.
For certain exceptional applications, additional requirements which are not covered by this practice may be specified upon agreement between the manufacturer and the purchaser. 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 chromium rich oxide surface layer, on which the corrosion resistance of these alloys depends.
Bright annealing entails heating the stainless steel to a suitably high temperature usually more than 1, degrees F, or 1, degrees C in a reducing atmosphere such as dry hydrogen gas.
Extreme chloride concentrations may develop because of evaporation in systems that are not properly drained, which negates the corrosion protection expected of stainless steels. Organic contaminants are volatilized and most metal oxides including those of iron, nickel, and chromium will be reduced, resulting in a clean, oxide-free surface.
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 completely, it is the latter interpretation of passivation that relates to establishing the corrosion resistance of stainless steels.
Parts treated however must pass specific asstm 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.
Keeping stainless steels stainless
If small regions of the surface are active, they will be readily attacked in a corrosive environment. This protective film develops when more than 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.
Although they apply primarily to materials in the composition ranges of the austenitic, ferritic, and martensitic stainless steels, the practices described may also be useful for cleaning other metals if due consideration is given to corrosion and possible metallurgical effects.
This condition can be measured using electrochemical techniques as a potential of 0. 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. Office and Postal Address: Some of the various meanings associated with the term passivation that are in common usage include the following:.
When the section was placed in service, a corrosive environment preferentially attacked the stainless steel surface under the heat tint. Stainless steels cannot be passivated unless the steel surface is clean and free from contamination and scale from welding operations.
ASTM A Passivation Standard | Able Electropolishing
While very effective as a passivator, this solution may have environmental ramifications. Citric acid treatments can also be considered as an alternative to nitric acid as both provide the oxidising conditions necessary for passivation. Die fully sensored and still getting miss-hits? 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.
It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
It is likely that the darker, thicker oxide tints are the result of the formation of an oxide with higher iron and magnesium content; that is, reduced chromium content. 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 orbital welding.
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.
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: It should be stressed that the protective oxide film formed during effective passivation of the stainless steel is transparent and not observable to the naked eye.
An example of reduced corrosion resistance is shown in Figure 1. Related Links Suppliers of Passivating Products.
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Thus, passivation may refer to the chemical removal of free iron or iron compounds from the surface, or it may refer to the spontaneous development of a chemically inactive surface protective oxide film on the stainless steel. Passivation is the process of forming a protective oxide film on stainless steel.
This condition will accelerate the rate of metal dissolution into the surrounding electrolyte. Such chemical treatment is generally not necessary for the formation of the passive film. Range C Time mins. The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath the oxide film.