A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. These acid solution that will remove the surface contamination but recommendations are presented as procedures for guidance will not significantly affect the stainless steel itself. This when it is recognized that for a particular service it is desired process is described in a general way in 6.
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Ask Document Center Inc. Scope 1. 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.
The selection of procedures from this practice to be applied to the parts may be specified upon agreement between the supplier and the purchaser. For certain exceptional applications, additional requirements which are not covered by this practice may be specified upon agreement between the supplier and the purchaser. Although they apply primarily to materials in the composition ranges of the austenitic, ferritic, martensitic, and duplex stainless steels, the practices described may also be useful for cleaning other metals if due consideration is given to corrosion and possible metallurgical effects.
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. Some of the various meanings associated with the term passivation that are in common usage include the following: 1.
It was at one time considered that an oxidizing treatment was necessary to establish this passive metal oxide 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. This process is described in a general way in 6. Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation.
Such chemical treatment is generally not necessary for the formation of the passive metal oxide film. Depending on the application, chemical descaling acid pickling as described in 5.
On the other hand, some of the practices may be applicable for these purposes. 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. It therefore in no way precludes the necessity for careful planning and judgment in the selection and implementation of such procedures.
The degree of cleanness required on a surface depends on the application. In some cases, no more than degreasing or removal of gross contamination is necessary. 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. Meaningful tests to establish the degree of cleanness of a surface are few, and those are often difficult to administer and to evaluate objectively.
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. In addition, visual inspection of internal surfaces is often impossible because of the configuration of the item. Methods are described for the detection of free iron and transparent chemical and oily deposits. Tests with acceptance criteria to demonstrate that the passivation procedures have been successful are listed in 7.
The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 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. For more specific safety precautions see 7.
Keywords austenitic stainless steels; cleaning; corrosion; corrosive service applications; descaling; duplex stainless steels; ferritic stainless steels; martensitic stainless steels; pickling; stainless steels ;; ICS Number Code