ASTM B912-02(2013)
(Specification)Standard Specification for Passivation of Stainless Steels Using Electropolishing
Standard Specification for Passivation of Stainless Steels Using Electropolishing
ABSTRACT
This specification covers the passivation by electropolishing of stainless steel alloys in the 200, 300, and 400 series, as well as precipitation-hardened alloys. Basis materials shall be free of clearly visible defects, and if necessary, shall undergo preparatory cleaning procedures prior to electropolishing. Post-coating procedures such as post dip and final rinsing shall be performed as well. The performance of the specimens during passivation shall be evaluated by one or more of the following procedures: water immersion test; humidity test; salt spray test; copper sulfate test; and modified ferroxyl test for free iron.
SCOPE
1.1 This specification covers the passivation of stainless steel alloys in the 200 (UNS2XXXX), 300 (UNS3XXXX), and 400 (UNS4XXXX) series, and the precipitation-hardened alloys, using electropolishing procedures.Note 1—Surface passivation occurs simultaneously with electropolishing under proper operating conditions. The quality of passivation will depend on the type of stainless steel, the formulation of the electropolishing solution, and the conditions of operation. Free iron on the surface of the stainless steel is removed resulting in improved corrosion resistance. Surface smoothing obtained by electropolishing will also improve corrosion resistance. Electropolishing will also remove heat tint and oxide scale.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This specification may involve hazardous materials, operations, and equipment. This specification does not purport to address all of the safety concerns, if any, associated with its use. 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.
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Designation:B912 −02 (Reapproved 2013)
Standard Specification for
Passivation of Stainless Steels Using Electropolishing
This standard is issued under the fixed designation B912; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D3951 Practice for Commercial Packaging
2.2 ISO Standards:
1.1 This specification covers the passivation of stainless
ISO 2080 Electroplating and Related Processes—
steel alloys in the 200 (UNS2XXXX), 300 (UNS3XXXX), and
Vocabulary
400 (UNS4XXXX) series, and the precipitation-hardened
ISO 4519 Electrodeposited Metallic Coatings and Related
alloys, using electropolishing procedures.
Finishes—Sampling Procedures for Inspection by Attri-
NOTE 1—Surface passivation occurs simultaneously with electropolish-
butes
ing under proper operating conditions. The quality of passivation will
ISO 9227 Corrosion Tests in Artificial Atmospheres—Salt
depend on the type of stainless steel, the formulation of the electropol-
Spray Tests
ishing solution, and the conditions of operation. Free iron on the surface
of the stainless steel is removed resulting in improved corrosion resis- ISO 15730 Metallic and Other Inorganic Coatings—
tance. Surface smoothing obtained by electropolishing will also improve
Electropolishing as a Means of Smoothing and Passivat-
corrosion resistance. Electropolishing will also remove heat tint and oxide
ing Stainless Steels
scale.
1.2 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 electropolishing, n—electrochemical process in which
1.3 This specification may involve hazardous materials,
the article(s) to be passivated are treated anodically in a
operations, and equipment. This specification does not purport
suitable acid medium.
to address all of the safety concerns, if any, associated with its
3.1.2 passivation, n—rendering of a stainless steel surface
use. It is the responsibility of the user of this standard to
into a lower state of chemical reactivity.
establish appropriate safety and health practices and deter-
3.1.2.1 Discussion—Passivated surfaces are characterized
mine the applicability of regulatory limitations prior to use.
by the absence of free iron, as defined by Practice A380.
3.2 Definitions of Terms Specific to This Standard:
2. Referenced Documents
3.2.1 Definitions of terms in this specification can be found
2.1 ASTM Standards:
in Terminology B374 and ISO 2080.
A380 Practice for Cleaning, Descaling, and Passivation of
Stainless Steel Parts, Equipment, and Systems
4. Ordering Information
A967 Specification for Chemical Passivation Treatments for
4.1 When ordering articles to be electropolished in confor-
Stainless Steel Parts
mance with this standard, the purchaser shall state the follow-
B117 Practice for Operating Salt Spray (Fog) Apparatus
ing:
B322 Guide for Cleaning Metals Prior to Electroplating
4.1.1 Alloy Designation—When ordering articles passivated
B374 Terminology Relating to Electroplating
in accordance with this specification, the purchaser shall state,
B602 Test Method for Attribute Sampling of Metallic and
in addition to theASTM designation number, the date of issue,
Inorganic Coatings
the alloy designation number, and the testing method(s) by
which the article will be evaluated (see 5.3).
4.1.2 Appearance—The purchaser shall specify the appear-
This specification is under the jurisdiction of ASTM Committee B08 on
ance required, for example, bright or dull. Unless otherwise
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.07 on Conversion Coatings.
specified by the purchaser, a bright luster shall be acceptable.
Current edition approved May 1, 2013. Published May 2013. Originally
Alternatively, samples showing the required finish, or range of
ε1
approved in 2002. Last previous edition approved in 2008 as B912 – 02 (2008) .
finish, shall be supplied or approved by the purchaser. When
DOI: 10.1520/B0912-02R13.
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
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
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B912−02 (2013)
required, the basis material may be subjected, before 5.2.4 Final Rinsing—Rinsing subsequent to passivation is
electropolishing, to such mechanical polishing as may be necessarytoremovealltracesofacidifiedwaterthatmayaffect
required to yield the desired final surface characteristics. the appearance and performance of the passive part. Deionized
4.1.3 Contact Marks—Visible contact marks may occur. or distilled water may be used to avoid water spots.
The location of electrical contact marks shall be agreed upon
5.3 Passivation Testing:
between purchaser and supplier.
5.3.1 Passivation by electropolishing shall be evaluated by
4.1.4 Metal Removal—Some metal is removed from the
one or more of the following test methods (see Section 6 for
surface of the article during electropolishing, typically 5 to 10
test procedures):
µm. As much as 50 µm may be removed for additional
5.3.1.1 Water immersion test,
smoothing.The ordering document shall include the maximum
5.3.1.2 Humidity test,
amount of metal to be removed.
5.3.1.3 Salt spray test,
4.1.5 Any requirement for certification—See Section 9.
5.3.1.4 Copper sulfate test, and
4.1.6 Any requirement for packaging—See Section 10.
5.3.1.5 Modified “ferroxyl” test for free iron.
5. Product Requirements
6. Test Procedures
5.1 Visual Defects—When specified, the significant surfaces
6.1 Water Immersion Test (Specification A967)—The ar-
of the article to be passivated by electropolishing shall be free
ticle(s) shall be alternately immersed in distilled water for 1 h,
of clearly visible defects such as pits, roughness, striations, or
then allowed to dry for 1 h for twelve wet-dry cycles (24 h
discoloration when examined with 20/20 eyesight at a distance
total). Failure is indicated by the presence of red rust or
of approximately 0.5 m.
staining as a result of the presence of free iron on the surface.
NOTE 2—Defects in the surface of the basis material such as scratches,
6.2 Humidity Test (Practice A380, Specification A967)—
porosity, inclusions, and so forth, may adversely affect the appearance and
The article(s) shall be subjected to 100 % humidity at 38 6
performance of the article. Visible examination shall include wearing
2°C in a suitable humidity cabinet for a period of 24 h. Failure
correctional glasses if the inspector normally wears them.
is indicated by the presence of red rust or staining as a result of
5.2 Process:
the presence of free iron on the surface.
5.2.1 Surface Preparation—Preparatory procedures and
6.3 Salt Spray (Fog) Testing (Practice B117 (ISO 9227))—
cleaning of the basis material may be necessary; see Practices
The article(s) shall be subjected to the prescribed test for a
A380 and B322.
minimum of 2 h in an accredited cabinet. Failure is indicated
5.2.2 Electropolishing—Following the preparatory
by the presence of red rust or staining as a result of the
operations, the articles are introduced into the electropolishing
presence of free iron on the surface.
solution for a period of time at the current density and
temperature required to produce the passive surface and
6.4 Copper Sulfate Test (Practice A380, Specification
required surface finish, if any.
A967)—See Appendix X2. The article is swabbed with an
acidified solution of copper sulfate. Failure is indicated by the
NOTE 3—A typical electropolishing solution and
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