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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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.
Article: Passivation of stainless steels
This condition can be measured using electrochemical techniques as a potential of 0. ASTM A sets forth several techniques to determine the presence of free iron a measure of qstm passivation on the surface of stainless steel.
This standard covers both nitric and citric acid treatments. Specifications for passivation treatments for stainless steels Traditionally the American standards have been used. For certain exceptional applications, additional requirements which are not covered by this practice may be specified upon agreement between the manufacturer and the purchaser. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
Methods are described for the detection of free iron and transparent chemical and oily deposits. The standard also allows any combination of citric acid concentration, astmm and time, provided that the w380-99 test criteria can be met. This test may be readily conducted on stainless steel sheet, tube, pipe, and fittings, as well as on welds and heat-affected zones HAZ. 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.
Many combinations of these variables can be used, but two of the most common are:. Preservation of the passive film requires the presence of oxygen in the environment to which the stainless steel is exposed. Figure 2 After removal of the heat tint oxide, evidence of in-service pitting in the HAZ is apparent.
Kuxhaus of MK Services Inc. This protective film develops when more than Figure 1 This interior view of a weld a830-99 on L exhibits the formation of heat tint on the weld and HAZ caused by the presence of oxygen during orbital welding. 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.
More Content by Carl R. The degree of cleanness required on a surface depends on the application. In both procedures the surface is cleaned of contaminants and the metal surface is subsequently oxidized.
It was at one time considered that an oxidizing treatment aatm 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. Naturally occurring conditions such air or aerated water will do this and so under many exposure conditions stainless steels will naturally self-passivate.
Process Class Stainless Steel Types C1 or C2 Austenitics, austenitic precipitation hardening and duplex C3 High chromium martensitics C4 Ferritics, martensitics and martensitic precipitation hardening.
Pickling, passivation and removing iron contamination with nitric acid Passivation treatments are sometimes specified, but it is important to consider whether this asfm strictly necessary or not. Others, such ast 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. However, some confusion still exists about the definition of passivation and what really causes a passive film to form on the surface of stainless steel.
He can be reached atfaxloper engr. EDTA is a chelating agent that keeps iron in solution over a wide pH range. The treatments are then defined by the process classes. If small regions of the surface are active, they will be readily attacked in a corrosive environment.
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.
Stainless steel’s corrosion resistance is due to a thin, chromium-rich, transparent oxide film on the surface 1.
On the other hand, some of the practices may be applicable for these purposes. Specific treatments are however also specified. It should be stressed that the protective oxide film formed during effective passivation of the stainless steel is transparent aztm not observable to the naked eye.
Meaningful tests to establish the degree of cleanness of a surface are few, and those are often difficult to administer and to evaluate objectively. 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.
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. For more specific safety precautions see 7. Link to Active This link will always route to the current Active version of a3380-99 standard.
This heat tint must be removed before the part is placed in service for optimum performance. 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.
Keeping stainless steels stainless
Acid concentrations up to 50 percent can be used, and the solution and residual effluent must be monitored closely. Related Links Suppliers of Passivating Products. Extreme chloride concentrations may develop because of evaporation in systems that are not properly drained, which negates the corrosion protection expected of asstm steels. Stainless steels cannot be passivated unless the steel surface is clean and free from contamination and scale from welding operations.