ASTM B136-84(1998)
(Test Method)Standard Method for Measurement of Stain Resistance of Anodic Coatings on Aluminum
Standard Method for Measurement of Stain Resistance of Anodic Coatings on Aluminum
SCOPE
1.1 This method is intended to determine whether anodic oxide coatings on aluminum and its alloys, that have undergone a sealing treatment and contact with an acid solution, are stainproof or nonadsorptive with respect to dyes.
1.2 Coatings that have been properly sealed should be proof against adsorption of coloring materials and, hence, "nonstaining" in many types of service.
1.3 This method is applicable to anodic coatings intended for applications where they are exposed to the weather, or for protective purposes in corrosive media, and where resistance to staining is important. Note 1-Performance in this test is predictive only of susceptibility to stain by dyes. It is not intended to be predictive of other factors in service performance such as pitting or general corrosion. Note 2-For Aluminum Association Class I and II architectural anodic coatings that are sealed in solutions containing less than 15 ppm silicates or 3 ppm phosphates, the acid pretreatment may be omitted.
1.4 In the case of coatings colored in deep shades, where estimation of the intensity of any residual dye stain is difficult, interpretation of the test is based on whether or not the original color has been affected by the action of the test.
1.5 This method is not applicable to:
1.5.1 Chromic acid type anodic coatings.
1.5.2 Anodic coatings on aluminum alloys containing more than 2 mass% Cu or 4.5 mass% Si.
1.5.3 Anodic coatings that have been sealed only in dichromate solutions.
1.5.4 Anodic coatings that have undergone a treatment to render them hydrophobic.
1.6 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of whoever uses this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B 136 – 84 (Reapproved 1998) Endorsed by American
Electroplaters’ Society
Endorsed by National
Association of Metal Finishers
Standard Method for
Measurement of Stain Resistance of Anodic Coatings on
Aluminum
This standard is issued under the fixed designation B 136; 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 2. Summary of Test Method
1.1 This method is intended to determine whether anodic 2.1 The method depends upon the observation that a non-
oxide coatings on aluminum and its alloys, that have under- sealed or poorly sealed anodic coating is attacked by acid and
gone a sealing treatment and contact with an acid solution, are easily colored by dye, while an adequately sealed coating is not
stainproof or nonadsorptive with respect to dyes. appreciably attacked and does not retain any dye stain.
1.2 Coatings that have been properly sealed should be proof 2.2 The method comprises contacting the test area of the
against adsorption of coloring materials and, hence, “nonstain- anodized specimen with nitric acid solution and, after rinsing
ing” in many types of service. and drying, applying a special dye solution followed by rinsing
1.3 This method is applicable to anodic coatings intended and rubbing the test area with pumice powder, drying, and
for applications where they are exposed to the weather, or for visual examination of the test area for retention of dye stain.
protective purposes in corrosive media, and where resistance to Coatings that exhibit no dye stain or change in color are
staining is important. considered to have passed the test.
NOTE 1—Performance in this test is predictive only of susceptibility to
3. Reagents
stain by dyes. It is not intended to be predictive of other factors in service
3.1 Purity of Reagents—Reagent grade chemicals shall be
performance such as pitting or general corrosion.
used in all tests. Unless otherwise indicated, it is intended that
NOTE 2—For Aluminum Association Class I and II architectural anodic
coatings that are sealed in solutions containing less than 15 ppm silicates
all reagents shall conform to the specifications of the Commit-
or 3 ppm phosphates, the acid pretreatment may be omitted.
tee on Analytical Reagents of the American Chemical Society,
where such specifications are available. Other grades may be
1.4 In the case of coatings colored in deep shades, where
used, provided it is first ascertained that the reagent is of
estimation of the intensity of any residual dye stain is difficult,
sufficiently high purity to permit its use without lessening the
interpretation of the test is based on whether or not the original
accuracy of the determination.
color has been affected by the action of the test.
3.2 Nitric Acid Solution—Prepare a 40 6 5 mass % solution
1.5 This method is not applicable to:
of nitric acid (HNO ) in distilled or deionized water.
1.5.1 Chromic acid type anodic coatings. 3
1.5.2 Anodic coatings on aluminum alloys containing more
NOTE 3—A convenient way is to carefully add one volume of 70 %
than 2 mass % Cu or 4.5 mass % Si.
HNO (sp gr 1.41 at 20°C) to an equal volume of water, while stirring,
1.5.3 Anodic coatings that have been sealed only in dichro- observing the normal precautions for handling strong acids.
mate solutions.
3.3 Special Dye Solution—Dissolve1gof aluminum blue
1.5.4 Anodic coatings that have undergone a treatment to 3
2LW dye in 50 mL of distilled or deionized water. The pH of
render them hydrophobic.
the dye test solution shall be adjusted to 5.0 6 0.5 and
1.6 This standard does not purport to address all of the
maintained at this value with additions of acetic acid or sodium
safety concerns, if any, associated with its use. It is the
hydroxide, as required.
responsibility of whoever uses this standard to consult and
NOTE 4—Dye solutions contaminated with soluble phosphates have
establish appropriate safety and health practices and deter-
reduced capability for staining nonsealed or poorly sealed anodic coatings.
mine the applicability of regulatory limitations prior to use.
“Reagent Chemicals, American Chemical Society Specifications,” Am. Chemi-
cal Soc., Washington, DC. For suggestions on the testing of reagents not listed by
This method is under the jurisdiction of ASTM Committee B-8 on Metallic and the American Chemical Society, see “Reagent Chemicals and Standards,” by Joseph
Inorganic Coatings and is the direct responsibility of Subcommittee B08.07 on Rosin
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