ASTM A380-99(2005)
(Practice)Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems
Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems
SCOPE
1.1 This practice covers recommendations and precautions for cleaning, descaling, and passivating of new stainless steel parts, assemblies, equipment, and installed systems. 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. For certain exceptional applications, additional requirements which are not covered by this practice may be specified upon agreement between the manufacturer and the purchaser. 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.
1.1.1 The term passivation is commonly applied to several distinctly different operations or processes relating to stainless steels. 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:
1.1.1.1 Passivation is the process by which a stainless steel will spontaneously form a chemically inactive surface when exposed to air or other oxygen-containing environments. 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.
1.1.1.2 Passivation is removal of exogenous iron or iron compounds from the surface of a stainless steel by means of a chemical dissolution, most typically by a treatment with an acid solution that will remove the surface contamination but will not significantly affect the stainlees steel itself. This process is described in a general way in 6.2.11 and defined precisely in 6.4 with further reference to the requirements of Annex A2 and Part II of the table on acid cleaning of steel. Unless otherwise specified, it is this definition of passivation that is taken as the meaning of a specified requirement for passivation.
1.1.1.3 Passivation is the chemical treatment of a stainless steel with a mild oxidant, such as a nitric acid solution, for the purpose of enhancing the spontaneous formation of the protective passive film. Such chemical treatment is generally not necessary for the formation of the passive film.
1.1.1.4 Passivation does not indicate the separate process of descaling as described in Section 5, although descaling may be necessary before passivation can be effective.
1.2 This practice does not cover decontamination or cleaning of equipment or systems that have been in service, nor does it cover descaling and cleaning of materials at the mill. 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.
1.3 These practices may be applied when free iron, oxide scale, rust, grease, oil, carbonaceous or other residual chemical films, soil, particles, metal chips, dirt, or other nonvolatile deposits might adversely affect the metallurgical or sanitary condition or stability of a surface, the mechanical operation of a part, component, or system, or contaminate a process fluid. The degree of cleanness required on a surface depends on the application. In some...
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Designation:A 380–99 (Reapproved 2005)
Standard Practice for
Cleaning, Descaling, and Passivation of Stainless Steel
Parts, Equipment, and Systems
This standard is issued under the fixed designation A 380; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope acid solution that will remove the surface contamination but
will not significantly affect the stainlees steel itself. This
1.1 This practice covers recommendations and precautions
process is described in a general way in 6.2.11 and defined
for cleaning, descaling, and passivating of new stainless steel
precisely in 6.4 with further reference to the requirements of
parts, assemblies, equipment, and installed systems. These
Annex A2 and Part II of the table on acid cleaning of steel.
recommendations are presented as procedures for guidance
Unless otherwise specified, it is this definition of passivation
when it is recognized that for a particular service it is desired
that is taken as the meaning of a specified requirement for
to remove surface contaminants that may impair the normal
passivation.
corrosion resistance, or result in the later contamination of the
1.1.1.3 Passivation is the chemical treatment of a stainless
particularstainlesssteelgrade,orcauseproductcontamination.
steel with a mild oxidant, such as a nitric acid solution, for the
For certain exceptional applications, additional requirements
purpose of enhancing the spontaneous formation of the protec-
which are not covered by this practice may be specified upon
tive passive film. Such chemical treatment is generally not
agreement between the manufacturer and the purchaser. Al-
necessary for the formation of the passive film.
though they apply primarily to materials in the composition
1.1.1.4 Passivation does not indicate the separate process of
ranges of the austenitic, ferritic, and martensitic stainless
descaling as described in Section 5, although descaling may be
steels, the practices described may also be useful for cleaning
necessary before passivation can be effective.
other metals if due consideration is given to corrosion and
1.2 This practice does not cover decontamination or clean-
possible metallurgical effects.
ingofequipmentorsystemsthathavebeeninservice,nordoes
1.1.1 The term passivation is commonly applied to several
it cover descaling and cleaning of materials at the mill. On the
distinctly different operations or processes relating to stainless
other hand, some of the practices may be applicable for these
steels. In order to avoid ambiguity in the setting of require-
purposes. While the practice provides recommendations and
ments,itmaybenecessaryforthepurchasertodefineprecisely
information concerning the use of acids and other cleaning and
the intended meaning of passivation. Some of the various
descaling agents, it cannot encompass detailed cleaning proce-
meanings associated with the term passivation that are in
dures for specific types of equipment or installations. It
common usage include the following:
thereforeinnowayprecludesthenecessityforcarefulplanning
1.1.1.1 Passivation is the process by which a stainless steel
and judgment in the selection and implementation of such
will spontaneously form a chemically inactive surface when
procedures.
exposedtoairorotheroxygen-containingenvironments.Itwas
1.3 These practices may be applied when free iron, oxide
at one time considered that an oxidizing treatment was neces-
scale, rust, grease, oil, carbonaceous or other residual chemical
sary to establish this passive film, but it is now accepted that
films, soil, particles, metal chips, dirt, or other nonvolatile
this film will form spontaneously in an oxygen-containing
deposits might adversely affect the metallurgical or sanitary
environment providing that the surface has been thoroughly
condition or stability of a surface, the mechanical operation of
cleaned or descaled.
a part, component, or system, or contaminate a process fluid.
1.1.1.2 Passivation is removal of exogenous iron or iron
The degree of cleanness required on a surface depends on the
compounds from the surface of a stainless steel by means of a
application.Insomecases,nomorethandegreasingorremoval
chemical dissolution, most typically by a treatment with an
of gross contamination is necessary. Others, such as food-
handling, pharmaceutical, aerospace, and certain nuclear ap-
This practice is under the jurisdiction of ASTM Committee A01 on Steel,
plications, may require extremely high levels of cleanness,
Stainless Steel, and RelatedAlloys and is the direct responsibility of Subcommittee
including removal of all detectable residual chemical films and
A01.14 on Methods of Corrosion Testing.
contaminants that are invisible to ordinary inspection methods.
Current edition approved May 1, 2005. Published May 2005. Originally
e1
approved in 1954. Last previous edition approved in 1999 as A 380 – 99 .
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A 380–99 (2005)
NOTE 1—The term “iron,” when hereinafter referred to as a surface
location where the cleaning is likely to be least effective; the
contaminant, shall denote free iron.
spool piece can then be removed for inspection upon comple-
tion of cleaning.
1.4 Attainment of surfaces that are free of iron, metallic
deposits,andothercontaminationdependsonacombinationof
4. Precleaning
proper design, fabrication methods, cleaning and descaling,
4.1 Precleaningistheremovalofgrease,oil,paint,soil,grit,
and protection to prevent recontamination of cleaned surfaces.
and other gross contamination preparatory to a fabrication
Meaningful tests to establish the degree of cleanness of a
process or final cleaning. Precleaning is not as critical and is
surface are few, and those are often difficult to administer and
generally not as thorough as subsequent cleaning operations.
to evaluate objectively. Visual inspection is suitable for the
Materials should be precleaned before hot-forming, annealing,
detection of gross contamination, scale, rust, and particulates,
or other high-temperature operation, before any descaling
but may not reveal the presence of thin films of oil or residual
operation, and before any finish-cleaning operation where the
chemical films. In addition, visual inspection of internal
parts will be immersed or where the cleaning solutions will be
surfaces is often impossible because of the configuration of the
reused. Items that are subject to several redraws or a series of
item. Methods are described for the detection of free iron and
hot-forming operations, with intermediate anneals, must be
transparent chemical and oily deposits.
cleaned after each forming operation, prior to annealing.
1.5 This standard does not purport to address all of the
Precleaning may be accomplished by vapor degreasing; im-
safety concerns, if any, associated with its use. It is the
mersion in, spraying, or swabbing with alkaline or emulsion
responsibility of the user of this standard to establish appro-
cleaners, steam, or high-pressure water-jet (see 6.2).
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. (For more specific
5. Descaling
safety precautions see 7.2.5.3, 7.3.4, Section 8, A1.7, and
5.1 General—Descaling is the removal of heavy, tightly
A2.11.)
adherent oxide films resulting from hot-forming, heat-
2. Referenced Documents
treatment, welding, and other high-temperature operations.
Because mill products are usually supplied in the descaled
2.1 ASTM Standards:
condition, descaling (except removal of localized scale result-
F21 Test Method for Hydrophobic Surface Films by the
ing from welding) is generally not necessary during fabrication
Atomizer Test
of equipment or erection of systems (see 6.3). When neces-
F22 Test Method for Hydrophobic Surface Films by the
sary, scale may be removed by one of the chemical methods
Water-Break Test
listed below, by mechanical methods (for example, abrasive
2.2 Federal Standard:
blasting, sanding, grinding, power brushing), or by a combi-
Fed. Std. No. 209e for Clean Room and Work Station
nation of these.
Requiring Controlled Environments
5.2 Chemical Descaling (Pickling)—Chemical descaling
3. Design agentsincludeaqueoussolutionsofsulfuric,nitric,andhydrof-
luoricacidasdescribedinAnnexA1,TableA1.1,moltenalkali
3.1 Consideration should be given in the design of parts,
or salt baths, and various proprietary formulations.
equipment, and systems that will require cleaning to minimize
5.2.1 Acid Pickling—Nitric-hydrofluoric acid solution is
the presence of crevices, pockets, blind holes, undrainable
most widely used by fabricators of stainless steel equipment
cavities, and other areas in which dirt, cleaning solutions, or
and removes both metallic contamination, and welding and
sludge might lodge or become trapped, and to provide for
heat-treating scales. Its use should be carefully controlled and
effective circulation and removal of cleaning solutions. In
is not recommended for descaling sensitized austenitic stain-
equipment and systems that will be cleaned in place or that
less steels or hardened martensitic stainless steels or where it
cannot be immersed in the cleaning solution, it is advisable to
can come into contact with carbon steel parts, assemblies,
slope lines for drainage: to provide vents at high points and
equipment, and systems. See alsoA1.3. Solutions of nitric acid
drains at low points of the item or system; to arrange for
alone are usually not effective for removing heavy oxide scale.
removal or isolation of parts that might be damaged by the
5.2.2 Surfaces to be descaled are usually precleaned prior to
cleaning solution or fumes from the cleaning solutions; to
chemical treatment. When size and shape of product permit,
provide means for attaching temporary fill and circulation
total immersion in the pickling solution is preferred. Where
lines; and to provide for inspection of cleaned surfaces.
immersion is impractical, descaling may be accomplished by
3.2 In a complex piping system it may be difficult to
(1) wetting the surfaces by swabbing or spraying; or (2)by
determine how effective a cleaning operation has been. One
partially filling the item with pickling solution and rotating or
methodofdesigninginspectabilityintothesystemistoprovide
rocking to slosh the solution so that all surfaces receive the
a short flanged length of pipe (that is, a spool piece) at a
required chemical treatment. The surface should be kept in
contact with agitated solution for about 15 to 30 min or until
inspection shows that complete scale removal has been accom-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
plished. Without agitation, additional exposure time may be
Standards volume information, refer to the standard’s Document Summary page on
required. If rocking or rotation are impracticable, pickling
the ASTM website.
solution may be circulated through the item or system until
Available from Standardization Documents Order Desk, Bldg 4 Section D, 700
Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. inspection shows that descaling has been accomplished.
A 380–99 (2005)
5.2.3 Over-pickling must be avoided. Uniform removal of should be of a stainless steel which is equal in corrosion
scale with acid pickling depends on the acid used, acid resistance to the material being worked on.
concentration, solution temperature, and contact time (see
5.3.3 Clean, previously unused abrasives, such as glass
Annex A1). Continuous exposure to pickling solutions for
beads or iron-free silica or alumina sand, are recommended for
more than 30 min is not recommended. The item should be
abrasive blasting. Steel shot or grit is generally not recom-
drained and rinsed after 30 min and examined to check the
mended because of the possibility of embedding iron particles.
effectiveness of the treatment. Additional treatment may be
The use of stainless steel shot or grit reduces the danger of
required. Most pickling solutions will loosen weld and heat-
rusting and iron contamination, but cannot completely elimi-
treating scale but may not remove them completely. Intermit-
nate the possibility of embedding residues of iron-oxide scale.
tent scrubbing with a stainless steel brush or fiber-bristle brush,
5.3.4 If a totally iron and scale free surface is required, most
in conjunction with pickling or the initial rinse, may facilitate
abrasive blasting may be followed by a brief acid dip (see
the removal of scale particles and products of chemical
Annex A2).
reaction (that is, pickling smut).
5.2.4 After chemical descaling, surfaces must be thoroughly
6. Cleaning
rinsed to remove residual chemicals; a neutralization step is
sometimes necessary before final rinsing. To minimize stain-
6.1 General—Cleaning includes all operations necessary
ing, surfaces must not be permitted to dry between successive
for the removal of surface contaminants from metals to ensure
steps of the acid descaling and rinsing procedure, and thorough
(1) maximum corrosion resistance of the metal; (2) prevention
drying should follow the final water rinse. Chemical descaling
of product contamination; and (3) achievement of desired
methods, factors in their selection, and precautions in their use
appearance. Cleanness is a perishable condition. Careful plan-
are described in the Metals Handbook. When chemical
ning is necessary to achieve and maintain clean surfaces,
descaling is necessary, it should be done while the part is in its
especially where a high degree of cleanness is required.
simplest possible geometry, before subsequent fabrication or
Selection of cleaning processes is influenced mainly by the
installation steps create internal crevices or undrainable spaces
type of contaminant to be removed, the required degree of
that may trap descaling agents, sludge, particles, or contami-
cleanness, and cost. If careful control of fabrication processes,
nated rinse water that might either result in eventual corrosion
sequencing of cleaning and fabrication operations, and mea-
or adversely affect operation of the item after it is placed in
sures to prevent recontamination of cleaned surfaces are
service.
exercised, very little special cleaning of the finished item or
5.3 Mechanical Descaling
...
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