Standard Practice for Testing Chromate Coatings on Zinc and Cadmium Surfaces1 This standard is issued under the fixed designation B; 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.

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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. Scope 1. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Referenced Documents 2. Terminology 3. A list of some expected protective values obtainable in a given salt spray test is shown in Appendix X2. Current edition approved Aug. Published January Originally published as B — 45 T. Last previous edition B — The designation of signi? NOTE 1—Colorless coatings are also referred to as clear-bright or blue-bright coatings. Conditioning 5. Oily or greasy surfaces should not be used for testing, and degreasing with organic solvents is not recommended.

Procedure 6. Unless otherwise speci? The chromate coating should not be removed or worn through to the underlying metal as a result of this treatment. Allow the drop to remain on the surface for 5 s. Remove the testing solution by blotting gently, taking care not to disturb any deposit that may have formed. A dark deposit or black stain is indicative of the absence of a coating. The pH of the solution should be between 5.

Any white precipitate formed during the initial preparation of the solution may be dissolved by small additions of acetic acid; provided that the pH is not reduced to a value below 5. Upon formation of a white precipitate thereafter, the solution should be discarded.

On an untreated surface, a black spot forms almost immediately. They may be produced by either chemical or electrochemical processes from solutions containing hexavalent chromium compounds with one or more of certain anions which act as activators,?

There is evidence that over an extended period, chromate coatings undergo some chemical changes even under ordinary conditions. These changes increase with increase in temperature.

Colorless or light iridescent coatings appear to be less sensitive to elevated temperatures than are heavy chromate coatings. In order to produce an acceptable coating, it is essential that the surface be properly cleaned and free of heavy metallic impurities such as lead, copper, and contamination speci?

The color and luster produced by a given treatment will depend to some extent on the surface condition of the metal to which it is applied and may vary from part to part, or even on one single part. All types 2 of zinc and cadmium coatings can be chromated, and there may or may not be differences in the protection afforded by the chromate depending on the type of coating and the method of processing, so the actual protection required should be established to the satisfaction of the manufacturer and the purchaser.

Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every?

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ASTM B201 (2014r)




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