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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ASTM A sets forth several techniques to determine the presence of free iron a measure of adequate passivation on the surface of stainless steel.
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Article: Passivation of stainless steels
The color of this film is a function of the film thickness that developed at various distances from the weld. Passivation typically is accomplished either through an appropriate bright annealing of the stainless steel or by subjecting the surface to an appropriate chemical treatment. Kuxhaus of MK Services Inc. Stainless steels cannot be passivated unless the steel surface is clean and free from contamination and scale from welding operations.
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. This condition can be measured using electrochemical techniques as a potential of 0. This protective film develops when more than For more specific safety precautions see 7.
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. 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.
On the other hand, some of the practices may be applicable for these purposes.
Organic contaminants are volatilized and most metal oxides including those of iron, nickel, atm chromium will be reduced, resulting in a clean, oxide-free surface. Stainless steel’s corrosion resistance is due to a thin, chromium-rich, transparent oxide film on the surface 1.
Methods are described for the detection of free iron and transparent chemical and oily deposits. 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 z380-99 spontaneously in an oxygen-containing environment providing that the surface has been thoroughly cleaned or descaled. This heat tint must be removed before the part is placed in service for optimum performance.
ASTM A Passivation Standard | Able Electropolishing
Specifications for passivation treatments for stainless steels Traditionally the American standards have been used. 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.
Bright annealing entails heating the wstm 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. Although they apply primarily to materials in the a380-9 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.
While the practice provides recommendations and information concerning the use of acids and a38-99 cleaning and descaling agents, it cannot encompass detailed cleaning procedures for specific types of equipment or installations.
Some of the various meanings associated with the term passivation that are in common usage include the following:. Thus, passivation may refer to the chemical removal of free iron or iron compounds asstm the surface, or it may refer to the spontaneous development of a chemically inactive surface protective oxide film on the stainless steel. It was at one time considered aastm an oxidizing treatment was necessary to establish this passive film, but it is now awtm that this film will form spontaneously in an oxygen-containing environment providing that the surface has been thoroughly cleaned or descaled.
This test may be readily conducted on stainless steel sheet, tube, pipe, and fittings, as well as on welds and heat-affected zones HAZ. Referenced Documents purchase a380-999 The documents listed below are referenced within the subject standard but are not provided as part of the standard.
This film is about 10 atoms, or 35 angstroms, thick 0. Under these conditions, the surface is passive, or resistant to corrosion. 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.
The standard also allows any combination of citric acid concentration, temperature and time, provided that the passivation test criteria can be met. 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.
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.
Keeping stainless steels stainless
In addition, visual inspection of internal surfaces is often impossible because of the configuration of the item. Related Links Suppliers of Passivating Products.
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. It therefore in no way precludes the necessity for careful planning and judgment in the selection and implementation of such procedures.