ASTM D1731-09(2020)

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: D1731 − 09 (Reapproved 2020)
Standard Practices for
Preparation of Hot-Dip Aluminum Surfaces for Painting
This standard is issued under the fixed designation D1731; 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 3.1.1 Solvent Cleaning, and
3.1.2 Chemical Treatments.
1.1 These practices describe procedures for the preparation
of hot-dip aluminum surfaces for painting. 3.2 These two types cover several methods as described in
Section 5. Variations in surface treatment produce end condi-
1.2 This standard may involve hazardous materials,
tions which differ and which do not necessarily yield identical
operations, and equipment. This standard does not purport to
results when paints are applied. Service conditions will dictate
address all of the safety concerns, if any, associated with its
the type of surface preparation that should be selected.
use. It is the responsibility of the user of this standard to
establish appropriate safety, health, and environmental prac-
4. Solvent Cleaning
tices and determine the applicability of regulatory limitations
prior to use.
4.1 The surfaces may be prepared for painting by any of the
1.3 This international standard was developed in accor-
methods for solvent cleaning described in 4.2 and 4.3.
dance with internationally recognized principles on standard-
4.2 Method 1—Manual swabbing or dip washing with a
ization established in the Decision on Principles for the
solvent such as mineral spirits or high flask solvent naphtha. It
Development of International Standards, Guides and Recom-
is extremely difficult to produce a clean metal surface by this
mendations issued by the World Trade Organization Technical
method. Accumulated contaminants in the solvent or on the
Barriers to Trade (TBT) Committee.
swab are frequently redeposited on the surface being prepared.
2. Referenced Documents
4.3 Method 2—Solvent spray cleaning in accordance with
Method A, Procedure 1 of Practice D609.
2.1 ASTM Standards:
D609 Practice for Preparation of Cold-Rolled Steel Panels
4.4 Method 3—Vapor degreasing in special equipment in
for Testing Paint, Varnish, Conversion Coatings, and
accordance with the latest revision of Method A, Procedure 2
Related Coating Products
of Practice D609, employing trichlorethylene or perchloreth-
2.2 Military Standards:
ylenevapor.Solventcleaningdoesnotdisturbthenaturaloxide
MIL-DTL-5541 Chemical Conversion Coatings on Alumi- film on the metal and may prove adequate for some applica-
num and Aluminum Alloys
tions.
MIL-C-15328 Specification for Acid Wash Primers
MIL-M-10578B Metal Conditioner and Rust Remover
5. Chemical Treatment
(Phosphoric Acid Type)
5.1 The surfaces may be prepared for painting by any of the
methods for chemical treatment (Note 1) described in 5.2 to
3. Types of Surface Preparations
5.9:
3.1 Two types of surface preparations are covered as fol-
NOTE 1—Materials and procedures employed in these methods of
lows:
treatment are available from a number of sources as proprietary com-
pounds or methods. Selection may be made from available sources. The
hexavalent chromium methods given are not recommended as hexavalent
ThesepracticesareunderthejurisdictionofASTMCommitteeB08onMetallic
chromium is a known carcinogen.
and Inorganic Coatings and are the direct responsibility of Subcommittee B08.07 on
Conversion Coatings.
5.2 Method 1, Alkaline Cleaners—Etching alkaline
Current edition approved May 1, 2020. Published May 2020. Originally
solutions, such as caustic soda, should be avoided because of
approved in 1960. Last previous edition approved in 2014 as D1731 – 09(2014).
the possibility of dissolving away the aluminum coating
DOI: 10.1520/D1731-09R20.
thereby exposing the base metal. Since inhibited alkaline
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
cleaners do not etch the surface, they can be used to remove
Standards volume information, refer to the standard’s Document Summary page on
grease, oil, and other organic solids from hot dip aluminum.
the ASTM website.
After alkali cleaning, the surface should be thoroughly rinsed
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098. with clean water. Most often alkaline-cleaned surfaces are
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D1731 − 09 (2020)
subsequently processed by one of the following methods, 5.7 Method 6, Carbonate Chromate Treatment (see Note
described in 5.3 – 5.9. 4)—This process comprises treatment in a 160 to 180 °F (71 to
82 °C) dilute solution of sodium carbonate and potassium
5.3 Method 2, Alcoholic Phosphoric Acid Cleaners—This
chromate for periods from 2 to 20 min, followed by a water
treatment involves the use of an aqueous solution of phos-
rinse. The surface is then given a final treatment in a 150 to
phoric acid with alcohol or other organic solvents, together
160 °F (66 to 71 °C), 5 % potassium dichromate solution
with wetting agents, emulsifying agents, etc. The solution may
followed by a final rinse. The treatment produces a thin,
be applied by swabbing or dipping (preferably at a temperature
adherent, conversion coating on the surface, increasing the
of 70 to 90 °F (21 to 32 °C)). The solution should remain on
corrosion resistance of the metal and promoting paint adhesion
the surface for several minutes, followed by thorough ri
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