ASTM B912-02(2018)
(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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B912 −02 (Reapproved 2018)
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 A967/A967M Specification for Chemical Passivation Treat-
ments for Stainless Steel Parts
1.1 This specification covers the passivation of stainless
B117 Practice for Operating Salt Spray (Fog) Apparatus
steel alloys in the 200 (UNS2XXXX), 300 (UNS3XXXX), and
B322 Guide for Cleaning Metals Prior to Electroplating
400 (UNS4XXXX) series, and the precipitation-hardened
B374 Terminology Relating to Electroplating
alloys, using electropolishing procedures.
B602 Test Method for Attribute Sampling of Metallic and
NOTE 1—Surface passivation occurs simultaneously with electropolish-
Inorganic Coatings
ing under proper operating conditions. The quality of passivation will
D3951 Practice for Commercial Packaging
depend on the type of stainless steel, the formulation of the electropol-
2.2 ISO Standards:
ishing solution, and the conditions of operation. Free iron on the surface
of the stainless steel is removed resulting in improved corrosion resis- ISO 2080 Electroplating and Related Processes—
tance. Surface smoothing obtained by electropolishing will also improve
Vocabulary
corrosion resistance. Electropolishing will also remove heat tint and oxide
ISO 4519 Electrodeposited Metallic Coatings and Related
scale.
Finishes—Sampling Procedures for Inspection by Attri-
1.2 The values stated in SI units are to be regarded as
butes
standard. No other units of measurement are included in this
ISO 9227 Corrosion Tests in Artificial Atmospheres—Salt
standard.
Spray Tests
1.3 This specification may involve hazardous materials, ISO 15730 Metallic and Other Inorganic Coatings—
operations, and equipment. This specification does not purport Electropolishing as a Means of Smoothing and Passivat-
ing Stainless Steels
to address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to
3. Terminology
establish appropriate safety, health, and environmental prac-
tices and determine the applicability of regulatory limitations
3.1 Definitions:
prior to use.
3.1.1 electropolishing, n—electrochemical process in which
1.4 This international standard was developed in accor-
the article(s) to be passivated are treated anodically in a
dance with internationally recognized principles on standard-
suitable acid medium.
ization established in the Decision on Principles for the
3.1.2 passivation, n—rendering of a stainless steel surface
Development of International Standards, Guides and Recom-
into a lower state of chemical reactivity.
mendations issued by the World Trade Organization Technical
3.1.2.1 Discussion—Passivated surfaces are characterized
Barriers to Trade (TBT) Committee.
by the absence of free iron, as defined by Practice A380/
A380M.
2. Referenced Documents
3.2 Definitions of Terms Specific to This Standard:
2.1 ASTM Standards:
3.2.1 Definitions of terms in this specification can be found
A380/A380M Practice for Cleaning, Descaling, and Passi-
in Terminology B374 and ISO 2080.
vation of Stainless Steel Parts, Equipment, and Systems
4. Ordering Information
4.1 When ordering articles to be electropolished in confor-
This specification is under the jurisdiction of ASTM Committee B08 on
mance with this standard, the purchaser shall state the follow-
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.07 on Conversion Coatings.
ing:
Current edition approved Oct. 1, 2018. Published October 2018. Originally
4.1.1 Alloy Designation—When ordering articles passivated
approved in 2002. Last previous edition approved in 2013 as B912 – 02 (2013).
in accordance with this specification, the purchaser shall state,
DOI: 10.1520/B0912-02R18.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B912 − 02 (2018)
in addition to theASTM designation number, the date of issue, 5.2.3.1 Where local conditions prevent the use of nitric acid
the alloy designation number, and the testing method(s) by (nitrates) for film removal, other options may be used as long
which the article will be evaluated (see 5.3). as the articles meet the requirements of 5.3.
4.1.2 Appearance—The purchaser shall specify the appear-
NOTE 5—A 60-g/L solution of citric acid has been used for film
ance required, for example, bright or dull. Unless otherwise
removal; however, note that this procedure may pose waste treatment
difficulties. The use of other mineral acids, such as sulfuric or hydrochlo-
specified by the purchaser, a bright luster shall be acceptable.
ric acids, is not recommended as the passive film may be compromised.
Alternatively, samples showing the required finish, or range of
Neutralization procedures such as immersion in alkaline solutions should
finish, shall be supplied or approved by the purchaser. When
not be used as they can have a tendency to “set” the residual film and
required, the basis material may be subjected, before
detract from appearance and performance.
electropolishing, to such mechanical polishing as may be
5.2.4 Final Rinsing—Rinsing subsequent to passivation is
required to yield the desired final surface characteristics.
necessarytoremovealltracesofacidifiedwaterthatmayaffect
4.1.3 Contact Marks—Visible contact marks may occur.
the appearance and performance of the passive part. Deionized
The location of electrical contact marks shall be agreed upon
or distilled water may be used to avoid water spots.
between purchaser and supplier.
5.3 Passivation Testing:
4.1.4 Metal Removal—Some metal is removed from the
5.3.1 Passivation by electropolishing shall be evaluated by
surface of the article during electropolishing, typically
one or more of the following test methods (see Section 6 for
5 to 10 µm.As much as 50 µm may be removed for additional
test procedures):
smoothing.The ordering document shall include the maximum
5.3.1.1 Water immersion test,
amount of metal to be removed.
5.3.1.2 Humidity test,
4.1.5 Any requirement for certification—See Section 9.
5.3.1.3 Salt spray test,
4.1.6 Any requirement for packaging—See Section 10.
5.3.1.4 Copper sulfate test, and
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/A967M)—
of the article to be passivated by electropolishing shall be free
The article(s) shall be alternately immersed in distilled water
of clearly visible defects such as pits, roughness, striations, or
for 1 h, then allowed to dry for 1 h for twelve wet-dry cycles
discoloration when examined with 20/20 eyesight at a distance
(24 h 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/A380M, Specification
porosity, inclusions, and so forth, may adversely affect the appearance and
A967/A967M)—The article(s) shall be subjected to 100 %
performance of the article. Visible examination shall include wearing
humidity at 38 6 2°C in a suitable humidity cabinet for a
correctional glasses if the inspector normally wears them.
period of 24 h. Failure is indicated by the presence of red rust
5.2 Process:
or staining as a result of the presence of free iron on the
5.2.1 Surface Preparation—Preparatory procedures and
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