ASTM B556-90(2023)

SIGNIFICANCE AND USE 4.1 The thickness of a decorative chromium coating is often critical to its performance. 4.2 This procedure is useful for an approximate determination when the best possible accuracy is not required. For more reliable determinations, the following methods are available: Methods B504, B568, and B588. 4.3 This test assumes that the rate of dissolution of the chromium by the hydrochloric acid under the specified conditions is always the same. SCOPE 1.1 This guide covers the use of the spot test for the measurement of thicknesses of electrodeposited chromium coatings over nickel and stainless steel with an accuracy of about ±20 % (Section 9). It is applicable to thicknesses up to 1.2 μm.2 Note 1: Although this test can be used for coating thicknesses up to 1.2 μm, there is evidence that the results obtained by this method are high at thicknesses greater than 0.5 μm.3 In addition, for coating thicknesses above 0.5 μm, it is advisable to use a double drop of acid to prevent depletion of the test solution before completion of the test. 1.2 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. 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.