ASTM B555-86(2012)
(Guide)Standard Guide for Measurement of Electrodeposited Metallic Coating Thicknesses by Dropping Test
Standard Guide for Measurement of Electrodeposited Metallic Coating Thicknesses by Dropping Test
SIGNIFICANCE AND USE
4.1 The thickness of a metal 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: Test Methods B487, B499, B504, and B568.
4.3 This test assumes that the rate of dissolution of the coating by the corrosive reagent under the specified conditions is always the same.
SCOPE
1.1 This guide covers the use of the dropping test to measure the thickness of electrodeposited zinc, cadmium, copper, and tin coatings. Note 1—Under most circumstances this method of measuring coating thicknesses is not as reliable or as convenient to use as an appropriate coating thickness gauge (see Test Methods B499, B504, and B568).
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B555 − 86(Reapproved 2012)
Standard Guide for
Measurement of Electrodeposited Metallic Coating
Thicknesses by Dropping Test
This standard is issued under the fixed designation B555; 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. Summary of Guide
3.1 A dropping test consists of applying dropwise a corro-
1.1 This guide covers the use of the dropping test to
sive solution, at a constant rate, to the electroplated surface,
measure the thickness of electrodeposited zinc, cadmium,
and measuring the time required to penetrate the coating and
copper, and tin coatings.
expose the substrate; this time is proportional to the coating
NOTE 1—Under most circumstances this method of measuring coating thickness.
thicknesses is not as reliable or as convenient to use as an appropriate
coating thickness gauge (see Test Methods B499, B504, and B568). 4. Significance and Use
4.1 The thickness of a metal coating is often critical to its
1.2 The values stated in SI units are to be regarded as
performance.
standard. No other units of measurement are included in this
standard. 4.2 This procedure is useful for an approximate determina-
tion when the best possible accuracy is not required. For more
1.3 This standard does not purport to address all of the
reliable determinations, the following methods are available:
safety concerns, if any, associated with its use. It is the
Test Methods B487, B499, B504, and B568.
responsibility of the user of this standard to establish appro-
4.3 This test assumes that the rate of dissolution of the
priate safety and health practices and determine the applica-
coating by the corrosive reagent under the specified conditions
bility of regulatory limitations prior to use.
is always the same.
2. Referenced Documents
5. Factors Affecting the Accuracy
2.1 ASTM Standards: 5.1 The following factors will affect the accuracy of a
B487 Test Method for Measurement of Metal and Oxide coating thickness measurement made by this method:
5.1.1 Cleanliness of Surface—Any foreign material on the
Coating Thickness by Microscopical Examination of
surface to be tested, including lacquer, grease, corrosion
Cross Section
products, and conversion coatings, will interfere with the test
B499 Test Method for Measurement of Coating Thicknesses
and must be removed. Tarnish and conversion coatings can
by the Magnetic Method: Nonmagnetic Coatings on
often be removed by mild burnishing with a soft, clean pencil
Magnetic Basis Metals
eraser.
B504 Test Method for Measurement of Thickness of Metal-
5.1.2 Concentration of Test Solution—Variation from the
lic Coatings by the Coulometric Method
stated concentrations will introduce an error unless the thick-
B568 Test Method for Measurement of Coating Thickness
ness factor is adjusted accordingly. Test solutions cannot be
by X-Ray Spectrometry
reused.
D1193 Specification for Reagent Water
5.1.3 Temperature—The thickness factor for a given
solution, being a function of the temperature, must be known
for the temperature at which the test is made. Specimens to be
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
tested should be allowed to reach room temperature before
Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on Test
testing.
Methods.
5.1.4 Dropping Rate—The thickness factor is also a func-
Current edition approved May 1, 2012. Published November 2013. Originally
approved in 1971. Last previous edition approved in 2007 as B555 – 86 (2007).
tionofthedroppingrate.ThethicknessfactorsgiveninSection
DOI: 10.1520/B0555-86R12.
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 Such tests were described by Hull, R. O., and Strausser, P., Monthly Review,
Standards volume information, refer to the standard’s Document Summary page on American Electroplaters Society, MRAEA, Vol 22, 1935, p. 9, and by Brenner, A.,
the ASTM website. Proceedings, American Electroplaters Society, AEPPB, Vol 27, 1939, p. 204.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B555 − 86 (2012)
10 are for a dropping rate of 100 drops/min and will remain 5.1.8 Detection of End Point—The end point (the time at
valid for the range of 95 to 105 drops/min. which the coating has been penetrated and the substrate
5.1.5 Solution Drainage—The thickness factors given in exposed) is characterized by a change in the appearance of the
Section 10 are valid only if the test solution is rapidly drained surface on which drops are falling. This is a matter of personal
off, as from a flat surface inclined 45° from the horizontal. The judgment and may not always be clearly defined, depending
test cannot be made on a horizontal surface or at a location that upon the coating-substrate combination and the extent of
does not permit rapid drainage. alloying, if any. Such errors may be minimized by standardiz-
5.1.6 Drop Size—Variation in drop size may alter the ing the test method with identical specimens with a known
penetration rate. The tip of the dropping apparatus should coating thickness determined by other means.
conform to the dimensions given in Fig. 1 and should be kept 5.1.9 Composition of Coating—The dropping tests de-
clean. scribed in this document are intended for use on nominally
5.1.7 Alloy Layer—The presence of an alloy layer at the “pure” coatings. The thickness factors listed in Section 10 are
coating-substrate interface may obscure the end point and expectedtovarywithgrossvariationsinthecompositionofthe
introduce an uncertainty as to the amount of alloy included in coating, as might result from codeposition of an alloying
the thickness measurement. component. The specific effects, on the thickness factors, of
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