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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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.
Unlike ASTM A, the standard does not require specific solutions for particular stainless steel grades or types, although 3 specific treatments are identified. In both procedures the surface is cleaned of contaminants and the metal surface is subsequently oxidized.
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.
The term “iron,” when hereinafter referred to as a surface contaminant, shall denote free iron. 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.
Keeping stainless steels stainless – The Fabricator
In addition, this standard also includes citric acid treatments. 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 asstm iron contamination on the surface of the parts.
The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath the oxide film. 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: In many instances of passivation a830-99, 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.
Related Links Suppliers of Passivating Products. In addition, visual inspection of internal surfaces is often impossible because of the configuration of the item. Office and Postal Address: In the interior a38-99 an orbitally welded section of L, the inner surface of the weld bead, and the adjacent HAZ, are a830-99 with a varicolored asm film, or heat tint.
Nitric acid alone can be used to remove light surface iron contamination after which the acid facilitates the passivation of the cleaned steel surface. Passivation treatments are sometimes specified, but it is important to consider whether this is strictly necessary or not. On one hand, ASTM A notes that “Passivation is a process by which a stainless steel will spontaneously form a chemically inactive surface when exposed to air or other oxygen-containing environments.
While the practice provides recommendations and information concerning the use of acids and other cleaning and descaling agents, it cannot encompass detailed cleaning procedures for specific types of equipment or installations.
An example of reduced corrosion resistance is shown in Figure 1.
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. This solution has high reactivity with free iron, is less sensitive to exposure time, is far less corrosive to other materials, is less costly, and is considered environmentally friendly when used properly.
The treatments are then defined by the process classes.
Article: Passivation of stainless steels
Today, it remains the only North American publication devoted to this industry and it has become the most trusted source of information for tube and pipe professionals. Kuxhaus of MK Services Inc. Meaningful tests to establish the degree of cleanness of a surface are few, and those are often difficult to administer and to evaluate objectively.
While very effective as a passivator, this solution may have environmental ramifications.
Some of the various meanings associated with the term passivation that are in common usage include the following: Such chemical treatment is generally not necessary for the formation of the passive film. Pickling, passivation and removing iron contamination with nitric acid Passivation treatments are sometimes specified, but it is awtm to consider whether this is strictly necessary or not.
You May Also Like. It therefore in no way precludes the necessity for careful planning and judgment in the selection and implementation of such procedures. Preservation of the passive film requires the presence of oxygen in the environment to which a380-999 stainless steel is exposed.
On the other hand, some of the practices may be applicable for these purposes. Naturally occurring conditions such air or aerated water will do this and so under many exposure conditions stainless steels will naturally self-passivate.
Figure 2 After removal of the heat tint oxide, evidence of in-service pitting in the HAZ is apparent. 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.
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.
ASTM A380 Passivation Standard
Link to Active This link will always route to the current Active version of the standard. The author would like to thank Monty B. The color of this film is a function of the film thickness that developed at various distances from the weld. This condition will accelerate the rate of metal dissolution into the surrounding electrolyte. This test may be readily conducted on stainless steel sheet, tube, pipe, and fittings, as well as on welds and heat-affected zones HAZ.
Stainless steels cannot be passivated unless the steel surface is clean and free from contamination and scale from welding operations. Some of the various meanings associated with the term passivation that are in common usage include the following:. 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.
This film is about 10 atoms, or 35 angstroms, thick 0. 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.
This heat tint must be removed before the part is placed in service for optimum performance.