ASTM D1732-03(2018)
(Practice)Standard Practices for Preparation of Magnesium Alloy Surfaces for Painting
Standard Practices for Preparation of Magnesium Alloy Surfaces for Painting
ABSTRACT
This specification covers chemical treatments and anodic treatments for preparation of magnesium alloy surfaces for printing. The procedure for preliminary treatment of surfaces using alkaline cleaners and acid cleaners are presented. Class I, type I (chrome pickle) surface preparation procedure is applicable to all forms of magnesium except certain special alloys containing silver. Class I, type II (sealed chrome pickle) surface preparation procedure is applicable to all types and forms of magnesium-based alloys, subject only to the limitations of class I, type I treatment. Class I, type III treatment is applicable to all types and forms of magnesium-based alloys except M1 alloy and certain rare-earth alloys similar to EK30A. Class II, type I (galvanic dichromate treatment) produce black coatings of good protective and pain-base qualities, and is applicable to all alloys and forms of magnesium, including M1 alloy. Class II, type II treatment is applicable to all forms and alloys of magnesium. Class II, type III treatment is applicable to all forms and alloys of magnesium, free from attachments or inserts of other metals.
SCOPE
1.1 These practices cover two classes of treatment for preparation of magnesium alloy surfaces for painting, as follows:
Class I—Chemical Treatments.
Class II—Anodic Treatments.
In general, the latter treatments are the more protective of the two classes. Mechanical (abrasive) treatments, solvent cleaning, alkaline solution treatments, and acid pickles not resulting in protective conversion coatings are suitable preliminary treatments only for metal to be exposed under mildly corrosive (indoor) exposures. When a high degree of corrosion protection and paint adhesion are desired, as in many outdoor environments, surface preparation by one of the above conversion-coat classes is necessary. The hexavalent chromium based methods given are not recommended as hexavalent chromium is a known carcinogen.
Note 1: Testing of Coatings—Quality control tests of coatings are frequently desirable, and these generally consist of exposures, with or without paint, to salt spray, humidity, or natural environments, with suitable procedures for assessing the degree of breakdown suffered after fixed time intervals. It is recommended that quality control tests of coatings shall be made as far as possible with high-purity material (for example AZ31A alloy),2 the inherent corrosion rate of which is relatively consistent from batch to batch and that precautions shall be taken to remove surface contamination before coatings are applied. Such contamination shall be removed by acid pickling to a depth of at least 0.001 in. (25 μm) per side.
1.2 This standard may involve hazardous materials, operations, and equipment. This standard 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. (See Note 11.)
1.3 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.
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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: D1732 − 03 (Reapproved 2018)
Standard Practices for
1
Preparation of Magnesium Alloy Surfaces for Painting
This standard is issued under the fixed designation D1732; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope tices and determine the applicability of regulatory limitations
prior to use. (See Note 11.)
1.1 These practices cover two classes of treatment for
1.3 This international standard was developed in accor-
preparation of magnesium alloy surfaces for painting, as
dance with internationally recognized principles on standard-
follows:
ization established in the Decision on Principles for the
Class I—Chemical Treatments.
Development of International Standards, Guides and Recom-
Class II—Anodic Treatments.
mendations issued by the World Trade Organization Technical
Ingeneral,thelattertreatmentsarethemoreprotectiveofthe
Barriers to Trade (TBT) Committee.
two classes. Mechanical (abrasive) treatments, solvent
cleaning, alkaline solution treatments, and acid pickles not
PRELIMINARY TREATMENT OF SURFACES
resultinginprotectiveconversioncoatingsaresuitableprelimi-
nary treatments only for metal to be exposed under mildly
2. Procedure
corrosive (indoor) exposures. When a high degree of corrosion
2.1 Certain anodic treatments simultaneously produce con-
protection and paint adhesion are desired, as in many outdoor
version coatings on, and remove contamination from, magne-
environments, surface preparation by one of the above
sium alloy surfaces. In general, however, apply conversion
conversion-coatclassesisnecessary.Thehexavalentchromium
coatings only to surfaces previously freed from all
based methods given are not recommended as hexavalent
contamination, including oxide, rolling-scale, corrosion
chromium is a known carcinogen.
product, burned-on drawing and forming lubricant, and the
NOTE 1—Testing of Coatings—Quality control tests of coatings are
contamination introduced by blast cleaning and fabrication
frequently desirable, and these generally consist of exposures, with or
operations. Contamination in or under surface conversion
without paint, to salt spray, humidity, or natural environments, with
coatings seriously reduces their protective values (Note 2). For
suitable procedures for assessing the degree of breakdown suffered after
the removal of tenacious surface contamination, such as
fixed time intervals. It is recommended that quality control tests of
coatings shall be made as far as possible with high-purity material (for rolling-scale or casting skin, an acid pickle to dissolve some of
2
exampleAZ31Aalloy), the inherent corrosion rate of which is relatively
the actual surface is essential. When organic contamination,
consistent from batch to batch and that precautions shall be taken to
such as grease or oil, is also present, an initial degreasing
remove surface contamination before coatings are applied. Such contami-
operation in solvent or in an alkaline degreasing solution is
nationshallberemovedbyacidpicklingtoadepthofatleast0.001in.(25
usually necessary to allow the subsequent acid to wet the
µm) per side.
surface. These matters are discussed in more detail under the
1.2 This standard may involve hazardous materials,
headings of the specific cleaners or treatments (Note 3), as
operations, and equipment. This standard does not purport to
follows:
address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to 2.2 Alkaline Cleaners—Oil, grease, and old (but not baked)
establish appropriate safety, health, and environmental prac-
chrome-pickle coatings are readily removed by most commer-
cially available heavy-duty alkaline cleaners; but such cleaners
are not suitable for removing oxide and the like, for which
1
ThesepracticesareunderthejurisdictionofASTMCommitteeB08onMetallic
purpose use acid pickles, preceded by alkaline cleaners.
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 on
Remove graphite lubricant and also baked chrome-pickle
Conversion Coatings.
coatings by a solution conforming to the following composi-
Current edition approved Oct. 1, 2018. Published October 2018. Originally
tion:
approved in 1960. Last previous edition approved in 2013 as D1732 – 03 (2013).
DOI: 10.1520/D1732-03R18.
Caustic soda (NaOH) 12 oz (90 g)
2
For info
...
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D1732 − 03 (Reapproved 2018)
Standard Practices for
1
Preparation of Magnesium Alloy Surfaces for Painting
This standard is issued under the fixed designation D1732; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope tices and determine the applicability of regulatory limitations
prior to use. (See Note 11.)
1.1 These practices cover two classes of treatment for
1.3 This international standard was developed in accor-
preparation of magnesium alloy surfaces for painting, as
dance with internationally recognized principles on standard-
follows:
ization established in the Decision on Principles for the
Class I—Chemical Treatments.
Development of International Standards, Guides and Recom-
Class II—Anodic Treatments.
mendations issued by the World Trade Organization Technical
In general, the latter treatments are the more protective of the
Barriers to Trade (TBT) Committee.
two classes. Mechanical (abrasive) treatments, solvent
cleaning, alkaline solution treatments, and acid pickles not
PRELIMINARY TREATMENT OF SURFACES
resulting in protective conversion coatings are suitable prelimi-
nary treatments only for metal to be exposed under mildly
2. Procedure
corrosive (indoor) exposures. When a high degree of corrosion
2.1 Certain anodic treatments simultaneously produce con-
protection and paint adhesion are desired, as in many outdoor
version coatings on, and remove contamination from, magne-
environments, surface preparation by one of the above
sium alloy surfaces. In general, however, apply conversion
conversion-coat classes is necessary. The hexavalent chromium
coatings only to surfaces previously freed from all
based methods given are not recommended as hexavalent
contamination, including oxide, rolling-scale, corrosion
chromium is a known carcinogen.
product, burned-on drawing and forming lubricant, and the
NOTE 1—Testing of Coatings—Quality control tests of coatings are
contamination introduced by blast cleaning and fabrication
frequently desirable, and these generally consist of exposures, with or
operations. Contamination in or under surface conversion
without paint, to salt spray, humidity, or natural environments, with
coatings seriously reduces their protective values (Note 2). For
suitable procedures for assessing the degree of breakdown suffered after
the removal of tenacious surface contamination, such as
fixed time intervals. It is recommended that quality control tests of
coatings shall be made as far as possible with high-purity material (for rolling-scale or casting skin, an acid pickle to dissolve some of
2
example AZ31A alloy), the inherent corrosion rate of which is relatively
the actual surface is essential. When organic contamination,
consistent from batch to batch and that precautions shall be taken to
such as grease or oil, is also present, an initial degreasing
remove surface contamination before coatings are applied. Such contami-
operation in solvent or in an alkaline degreasing solution is
nation shall be removed by acid pickling to a depth of at least 0.001 in. (25
usually necessary to allow the subsequent acid to wet the
µm) per side.
surface. These matters are discussed in more detail under the
1.2 This standard may involve hazardous materials,
headings of the specific cleaners or treatments (Note 3), as
operations, and equipment. This standard does not purport to
follows:
address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to
2.2 Alkaline Cleaners—Oil, grease, and old (but not baked)
establish appropriate safety, health, and environmental prac- chrome-pickle coatings are readily removed by most commer-
cially available heavy-duty alkaline cleaners; but such cleaners
are not suitable for removing oxide and the like, for which
1
These practices are under the jurisdiction of ASTM Committee B08 on Metallic purpose use acid pickles, preceded by alkaline cleaners.
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 on
Remove graphite lubricant and also baked chrome-pickle
Conversion Coatings.
coatings by a solution conforming to the following composi-
Current edition approved Oct. 1, 2018. Published October 2018. Originally
tion:
approved in 1960. Last previous edition approved in 2013 as D1732 – 03 (2013).
DOI: 10.1520/D1732-03R18.
Caustic soda (NaOH) 12 oz (90 g)
2
For information concerning magnesium and aluminum alloys, see ASTM
Wetting agent 0.1 oz (0.74 g)
Specification
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D1732 − 03 (Reapproved 2013) D1732 − 03 (Reapproved 2018)
Standard Practices for
1
Preparation of Magnesium Alloy Surfaces for Painting
This standard is issued under the fixed designation D1732; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope
1.1 These practices cover two classes of treatment for preparation of magnesium alloy surfaces for painting, as follows:
Class I—Chemical Treatments.
Class II—Anodic Treatments.
In general, the latter treatments are the more protective of the two classes. Mechanical (abrasive) treatments, solvent cleaning,
alkaline solution treatments, and acid pickles not resulting in protective conversion coatings are suitable preliminary treatments
only for metal to be exposed under mildly corrosive (indoor) exposures. When a high degree of corrosion protection and paint
adhesion are desired, as in many outdoor environments, surface preparation by one of the above conversion-coat classes is
necessary. The hexavalent chromium based methods given are not recommended as hexavalent chromium is a known carcinogen.
NOTE 1—Testing of Coatings—Quality control tests of coatings are frequently desirable, and these generally consist of exposures, with or without paint,
to salt spray, humidity, or natural environments, with suitable procedures for assessing the degree of breakdown suffered after fixed time intervals. It is
2
recommended that quality control tests of coatings shall be made as far as possible with high-purity material (for example AZ31A alloy), the inherent
corrosion rate of which is relatively consistent from batch to batch)batch and that precautions shall be taken to remove surface contamination before
coatings are applied. Such contamination shall be removed by acid pickling to a depth of at least 0.001 in. (25 μm) per side.
1.2 This standard may involve hazardous materials, operations, and equipment. This standard 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 safety, health, and healthenvironmental practices and determine the applicability of regulatory limitations prior to use. (See
Note 11.)
1.3 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.
PRELIMINARY TREATMENT OF SURFACES
2. Procedure
2.1 Certain anodic treatments simultaneously produce conversion coatings on, and remove contamination from, magnesium
alloy surfaces. In general, however, apply conversion coatings only to surfaces previously freed from all contamination, including
oxide, rolling-scale, corrosion product, burned-on drawing and forming lubricant, and the contamination introduced by blast
cleaning and fabrication operations. Contamination in or under surface conversion coatings seriously reduces their protective
values (Note 2). For the removal of tenacious surface contamination, such as rolling-scale or casting skin, an acid pickle to dissolve
some of the actual surface is essential. When organic contamination, such as grease or oil, is also present, an initial degreasing
operation in solvent or in an alkaline degreasing solution is usually necessary to allow the subsequent acid to wet the surface. These
matters are discussed in more detail under the headings of the specific cleaners or treatments (Note 3), as follows:
2.2 Alkaline Cleaners—Oil, grease, and old (but not baked) chrome-pickle coatings are readily removed by most commercially
available heavy-duty alkaline cleaners; but such cleaners are not suitable for removing oxide and the like, for which purpose use
acid pickles, preceded by alkaline cleaners. Remove graphite lubricant and also baked chrome-pickle coatings by a solution
conforming to the following composition:
1
These practices are under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 on
Conversion Coatings.
Current edition appro
...
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