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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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.
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. 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.
Best performance is achieved with a A3380-99 ratio of the surface oxide of more than 1. Many combinations of these variables can be used, but two of the most common are:.
The treatments are then defined by the process classes.
ASTM A380 Passivation Standard
Figure 2 After removal of the heat tint oxide, evidence of in-service pitting in the HAZ is apparent. While very effective as a passivator, this solution may have environmental ramifications. Nitric acid alone can be asfm to remove light surface iron contamination after which the acid facilitates the passivation of the cleaned steel surface.
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 sstm 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. Methods are described for the detection of free iron and transparent chemical and oily deposits.
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. In some cases, no more than degreasing or removal of gross contamination is necessary.
On the other hand, some of the practices may be applicable for these purposes. Passivation typically is accomplished either through an appropriate bright annealing of the stainless steel or by subjecting the surface to an appropriate chemical treatment. Active view current version of standard.
Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard.
ASTM A sets forth several techniques to determine the presence of free iron a measure of adequate passivation on the surface of stainless steel. When the section was placed in service, a corrosive environment preferentially attacked the stainless steel surface under the heat a3800-99.
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Passivation is the process of forming a protective oxide film on stainless steel. 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.
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.
This protective film develops when more than The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath the oxide film. While the practice provides recommendations and information concerning the use of acids and other cleaning atsm descaling agents, it cannot encompass detailed cleaning procedures for specific types of equipment or installations.
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. 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. Kuxhaus of MK Services Inc.
Keeping stainless steels stainless – The Fabricator
The stainless steel then is rapidly cooled through the temperature range of 1, and degrees F, or and degrees C to inhibit carbide precipitation, and then at lower temperatures exposed to air, where the protective oxide film forms spontaneously. EDTA is a chelating agent that keeps iron in solution over a wide pH range.
Some of the various meanings associated with the term passivation that are in common usage include the following:. Extreme chloride concentrations may develop because of evaporation in systems that are not properly drained, which negates the corrosion protection expected of stainless steels.
Evidence of in-service pitting in the heat tint in the HAZ may be seen in Figure 2. Preservation of the passive film requires the presence of oxygen in the environment to which the stainless steel is exposed.
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 presence of any free iron inadequate passivation is indicated by the deposition of copper on the surface where free iron is present.
This condition can be measured using electrochemical techniques as a potential of 0.
Article: Passivation of stainless steels
This condition will accelerate the rate of metal dissolution into the surrounding electrolyte. Citric acid is a less hazardous method and has environmental benefits in terms of ‘NOx’ fume emission and waste acid disposal.
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.
For more specific safety precautions see 7.
Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation. 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 a3800-99 friendly when used properly.
In addition, visual inspection of internal surfaces is often impossible because of the configuration of the item. 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.
Acid concentrations up to 50 percent can be used, and the solution and residual effluent must be monitored closely. Specifications for passivation treatments for stainless qstm Traditionally the American q380-99 have been used.
This heat tint must be removed before the part is placed in service for optimum performance. Die fully sensored and still getting miss-hits?