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.
Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation. 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: Naturally occurring conditions such air or aerated water will do this and so under many exposure conditions stainless steels will naturally self-passivate.
This film is about 10 atoms, or 35 angstroms, thick 0. 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 astmm residual chemical films.
Specifications for passivation treatments for stainless steels Traditionally the American standards have been used.
ASTM A380 Passivation Standard
Acid concentrations up to 50 percent can be used, and the solution and residual effluent must be monitored closely. 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. Evidence of in-service pitting in the heat tint in the HAZ may be seen in Figure 2.
Kuxhaus of MK Services Inc. 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. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Active view current version of standard. This condition can be measured using electrochemical techniques as a potential of 0.
Some of the various meanings associated with the term passivation that are in common usage include the following:. This process is described in a general way in 3a80-99. An sstm of reduced corrosion resistance is shown in Figure 1. Citric acid treatments can also be considered as an alternative to nitric acid as both provide the oxidising conditions necessary for passivation.
This protective film develops when more than In the interior of an orbitally welded section of L, the inner surface of the weld bead, and the adjacent HAZ, are covered with a varicolored oxide film, or heat tint. The standard also allows any combination aetm citric astk concentration, temperature and time, provided that the passivation test criteria can be met.
In the case of classes C3 and C4, a two step process is defined, x380-99 a clean water rinse between the two steps, shown in the table below. The degree of cleanness required on a surface depends on the application.
Article: Passivation of stainless steels
Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation. Meaningful tests to establish the degree of cleanness of a surface are few, and those are often difficult to administer and to evaluate objectively.
Best performance is achieved with a Cr-Fe ratio of the surface oxide of more than 1. 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.
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.
This heat tint must be removed before the part is placed in service for optimum performance.
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 treatments are then defined by the process classes.
ASTM A Passivation Standard | Able Electropolishing
Many combinations of these variables can be used, but two of the most common are:. Specific treatments are however also specified. He can be reached atfaxloper engr. On the other hand, ASTM A also notes that “Passivation is removal of exogenous or free iron or iron compounds from the surface of a stainless steel by chemical dissolution, most typically by a treatment with an acid solution that will remove the surface contamination but will not significantly affect the stainless steel itself.
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. 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.
In many instances of passivation failure, or corrosion attack, the integrity of the passive oxide film is compromised by the concentration of halide ions, for example, chlorine, which chemically attacks the oxide film.
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.
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Preservation of the passive film requires the presence of oxygen in the environment to which the stainless steel is exposed. While it is essential that surface contamination be removed completely, it is the latter interpretation of passivation that relates a80-99 establishing the corrosion resistance of stainless steels.
This solution has high reactivity with free iron, is less asrm to exposure time, is far less corrosive to other materials, is less costly, and is considered environmentally friendly when used properly. You May Also Like.
Such chemical treatment is generally not necessary for the formation of the passive film. The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath the oxide film.
Extreme chloride concentrations may develop because of evaporation in systems that are not properly drained, which negates the corrosion protection expected of stainless steels. 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 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. If small regions of the surface are active, they will be readily attacked in a corrosive environment. 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. 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.
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. In some cases, no more than degreasing or removal of gross contamination is necessary.