ASTM D7396-07

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Designation: D 7396 – 07
Standard Guide for
Preparation of New, Continuous Zinc-Coated (Galvanized)
Steel Surfaces for Painting
This standard is issued under the fixed designation D 7396; 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 Surface Preparation Specification No. 2 Hand Tool Clean-
ing
1.1 This guide covers surface cleaning and eight methods of
Surface Preparation Specification No. 3 Power Tool Clean-
treating new zinc-coated by the continuous process (galva-
ing
nized) surfaces produced by either the hot-dip method or by
Surface Preparation Specification No. 7 Brush-Off Blast
electroplating. This guide covers surfaces that have not been
Cleaning
treated previously at the mill to provide temporary protection
Paint Specification No. 27 Basic Zinc Chromate-Vinyl Bu-
against staining by moisture other than by easily removed
tyral Wash Primer
protective oils (see Appendix X1). For preparing surfaces of
new or weathered items of zinc-coated steel produced by batch
3. Summary of Guide
processing, refer to Practice D 6386.
3.1 This guide describes surface cleaning and treatment
1.2 The values stated in SI units are to be regarded as the
methods that provide galvanized surfaces suitable for painting,
standard. The values given in parentheses are for information
specifically so that an applied coating system can develop the
only.
adhesion necessary for satisfactory service life.
1.3 This standard does not purport to address all of the
3.2 Eight methods of treatment (Note 1 and Note 2) are
safety concerns, if any, associated with its use. It is the
covered as follows:
responsibility of the user of this standard to establish appro-
3.2.1 Method A—Zinc Phosphate Treatment.
priate safety and health practices and determine the applica-
3.2.2 Method B—Chromate Treatment.
bility of regulatory limitations prior to use.
3.2.3 Method C—Aqueous Chromic-Organic Treatment.
2. Referenced Documents 3.2.4 Method D—Acid-Curing Resinous Treatment.
3.2.5 Method E—Annealing Heat Treatments.
2.1 ASTM Standards:
3.2.6 Method F—Amorphous Complex-Oxide Treatment.
A 780 Practice for Repair of Damaged and UncoatedAreas
3.2.7 Method G—Abrasive Blast Cleaning.
of Hot-Dip Galvanized Coatings
3.2.8 Method H—Fluro-Titanic/Zirconic Polymer Treat-
D 6386 Practice for Preparation of Zinc (Hot-Dip Galva-
ment.
nized) Coated Iron and Steel Product and Hardware
Surfaces for Painting
NOTE 1—Materials employed in these methods of treatment are avail-
D 6492 Practice for Detection of Hexavalent Chromium On able from a number of sources as proprietary compounds or methods.
Selection may be made from available sources.
Zinc and Zinc/Aluminum Alloy Coated Steel
NOTE 2—The use of solvents containing volatile organic compounds to
2.2 SSPC—TheSocietyforProtectiveCoatingsStandards:
prepare or treat the surface of metal components contributes to air
Surface Preparation Specification No. 1 Solvent Cleaning
pollution in the same manner as the use of solvent containing paints and
coatings. The user of this guide must determine the applicability of
appropriate regulations governing the volatile organic compound content
of the materials used in a shop application (Miscellaneous Metal Parts),
This guide is under the jurisdiction of ASTM Committee D01 on Paint and
field painting (Architectural), or specific process industry.
Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.46 on Industrial Protective Coatings.
3.3 Variationsinsurfacepreparationproduceendconditions
Current edition approved Nov. 1, 2007. Published November 2007.
that differ and hence do not necessarily yield identical results
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
when paints are subsequently applied. Service conditions will
Standards volume information, refer to the standard’s Document Summary page on
dictate the type of surface preparation to be selected, although
the ASTM website.
the quality produced by any individual method may vary with
Available from Society for Protective Coatings (SSPC), 40 24th St., 6th Floor,
Pittsburgh, PA 15222-4656, http://www.sspc.org. different zinc coatings.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7396–07
3.4 Galvanized surfaces are treated by using various meth- should be used to wipe the galvanized parts. Warning—These
ods and apparatus; satisfactory application may be made at the rags or brushes should be cleaned or recycled often, since oil
following locations: can accumulate on their surfaces and be transferred back to the
galvanized part. Small parts may be dipped or cleaned in
Mill Plant Field
Method A Y Y Y
ultrasonic baths of solvents.After cleaning, rinse thoroughly in
Method B Y Y .
hot water or water under pressure. Allow to dry completely
Method C Y Y .
before proceeding.
Method D Y Y Y
Method E Y . .
3.6.3 Hand or Power Tool Cleaning—Hand or power tool
Method F Y Y .
cleaning may be used to clean light deposits of zinc reaction
Method G Y Y Y
Method H Y Y . by-products, such as wet storage stain, as specified in SSPC
Surface Preparation Specification 2 or 3.
3.5 This guide does not describe the cleaning necessary to
provide a zinc-coated (galvanized) surface suitable for the
4. Significance and Use
application of the treatments. Many cleaning methods are
applicable and the preferred method should be agreed upon 4.1 This guide describes procedures that can be used to
prepare new zinc-coated surfaces for painting and improve the
between the purchaser and the supplier.
bond of paint to the zinc surface.
NOTE 3—Most producers of zinc-coated (galvanized) steel sheets and
coils have adopted the practice of applying an inhibitor to the zinc surface
5. Processes
to give temporary protection against staining by moisture during shipping
or storage. Some of these inhibitors interfere with proper reaction of most
5.1 Method A, Zinc Phosphate Treatment—This
ofthetreatmentsdescribedinthesemethods,andanunsatisfactorysurface
conversion-coatingmethodconsistsofreactingthezincsurface
for painting results. It is strongly recommended that the purchaser consult
in a zinc acid phosphate solution containing oxidizing agents
thesupplierofthechemicaltreatmenttobeusedastothesuitabilityofthe
and other salts for accelerating the coating action. The zinc
zinc surfaces for treatment by any of these methods.
surface is converted to a crystalline phosphate coating of the
3.6 Surface Cleaning—Galvanized surfaces must be clean
proper texture to inhibit corrosion and increase the adherence
and free of oil and grease before they are treated. Adhesion
and durability of the paint film. Such treatments are recom-
problems have been experienced with newly galvanized ar-
mended for product finishes and may be carried out by
ticles that have been water quenched or treated with chromate
immersion, spray, or brush application.
conversion coatings. These two post-galvanizing processes,
5.2 Method B, Chromate Treatment—This treatment con-
water quenching and chromate conversion coating, are not
sists of a dip or spray with a dilute solution of a mixture of
recommended for galvanized articles that are to be treated
chromium trioxide and other acids, with the proper accelerator,
before painting. The presence of chromate conversion coatings
for a period from 5 to 30 s at room temperature to 55°C
on the surface of the galvanized steel can be detected using
(130°F) to provide a thin amorphous chromate coating that
Practice D 6492.
increases corrosion resistance and paint adhesion.
3.6.1 AqueousAlkalineCleaning—An alkaline solution, pH
5.3 Method C, Aqueous Chromic-Organic Treatments—
in the range of 11 to 12 definitely not greater than 13, can be
Certain water-soluble resins, when properly formulated with
used to remove traces of oil, grease, or dirt.An alkaline cleaner
chromium compounds, may be applied to zinc surfaces by
is unsuitable for removal of heavy build-up of zinc oxide or
roller coat or other suitable means, such as dip and squeegee
wet storage stain. See the American Galvanizers Publication,
rolls. Th
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