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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In both procedures the surface is cleaned of contaminants and the metal surface is subsequently oxidized. In addition, visual inspection of internal surfaces is often impossible because of the configuration of the item. Related Links Suppliers of Passivating Products. 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.
The treatments are then defined by the process classes. The presence of any free iron inadequate passivation is indicated by the deposition of copper on the surface where free iron is present. Unless otherwise specified, it is this definition of passivation that is taken as the meaning of xstm specified requirement for passivation. Specifications for passivation treatments for stainless steels Traditionally the American standards have been used. 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. While it is essential that w380-99 contamination be removed completely, it is the latter interpretation of passivation that relates to establishing the corrosion resistance of stainless steels.
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. Die fully sensored and still getting miss-hits?
Keeping stainless steels stainless – The Fabricator
Meaningful tests to establish the degree of cleanness of a surface are few, and asm are often difficult to administer and to evaluate objectively.
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. Citric acid treatments can also be considered as an alternative to nitric acid as both provide the oxidising conditions necessary for passivation.
This condition will accelerate the rate of metal dissolution into the surrounding electrolyte. 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.
Typical chemical treatment involves exposing the stainless steel surface to an oxidizing acid solution in which the significant variables are time, temperature, and concentration. Stainless steel’s corrosion resistance is due to a thin, chromium-rich, transparent oxide film on aetm surface 1. 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. 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; aetm heavier, darker oxide films will require pickling solutions.
When the section was placed in service, a corrosive environment preferentially attacked the stainless steel surface under the heat tint.
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The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath the oxide film. It a380-9 in no way precludes the necessity for careful planning and judgment in the selection and implementation of such procedures. ASTM A sets forth several techniques to determine the presence of free iron a measure of adequate passivation on the surface of stainless steel.
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.
Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation. 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.
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. 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.
Active view current version of standard. It is z380-99 that the entire surface be in a passive condition. 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.
Specific treatments are however also specified. 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.
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.
Acid concentrations up to 50 percent can be used, and the solution and residual effluent must be monitored closely.