ASTM B555-86(2007)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: B555 − 86 (Reapproved2007)
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 and measuring the time required to penetrate the coating and
expose the substrate; this time is proportional to the coating
1.1 This guide covers the use of the dropping test to
thickness.
measure the thickness of electrodeposited zinc, cadmium,
copper, and tin coatings.
4. Significance and Use
NOTE 1—Under most circumstances this method of measuring coating
4.1 The thickness of a metal coating is often critical to its
thicknesses is not as reliable or as convenient to use as an appropriate
performance.
coating thickness gauge (see Test Methods B499, B504, and B568).
4.2 This procedure is useful for an approximate determina-
1.2 This standard does not purport to address all of the
tion when the best possible accuracy is not required. For more
safety concerns, if any, associated with its use. It is the
reliable determinations, the following methods are available:
responsibility of the user of this standard to establish appro-
Test Methods B487, B499, B504, and B568.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4.3 This test assumes that the rate of dissolution of the
coating by the corrosive reagent under the specified conditions
2. Referenced Documents
is always the same.
2.1 ASTM Standards:
5. Factors Affecting the Accuracy
B487 Test Method for Measurement of Metal and Oxide
Coating Thickness by Microscopical Examination of
5.1 The following factors will affect the accuracy of a
Cross Section
coating thickness measurement made by this method:
B499 Test Method for Measurement of Coating Thicknesses
5.1.1 Cleanliness of Surface—Any foreign material on the
by the Magnetic Method: Nonmagnetic Coatings on
surface to be tested, including lacquer, grease, corrosion
Magnetic Basis Metals
products, and conversion coatings, will interfere with the test
B504 Test Method for Measurement of Thickness of Metal-
and must be removed. Tarnish and conversion coatings can
lic Coatings by the Coulometric Method
often be removed by mild burnishing with a soft, clean pencil
B568 Test Method for Measurement of Coating Thickness
eraser.
by X-Ray Spectrometry
5.1.2 Concentration of Test Solution—Variation from the
D1193 Specification for Reagent Water
stated concentrations will introduce an error unless the thick-
ness factor is adjusted accordingly. Test solutions cannot be
3. Summary of Guide
reused.
3.1 A dropping test consists of applying dropwise a corro-
5.1.3 Temperature—The thickness factor for a given
sive solution, at a constant rate, to the electroplated surface, solution, being a function of the temperature, must be known
for the temperature at which the test is made. Specimens to be
tested should be allowed to reach room temperature before
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
testing.
Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on Test
5.1.4 Dropping Rate—The thickness factor is also a func-
Methods.
Current edition approved March 1, 2007. Published March 2007. Originally
tionofthedroppingrate.ThethicknessfactorsgiveninSection
approved in 1971. Last previous edition approved in 2002 as B555 – 86 (2002).
10 are for a dropping rate of 100 drops/min and will remain
DOI: 10.1520/B0555-86R07.
valid for the range of 95 to 105 drops/min.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1.5 Solution Drainage—The thickness factors given in
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
Section 10 are valid only if the test solution is rapidly drained
the ASTM website.
off, as from a flat surface inclined 45° from the horizontal. The
Such tests were described by Hull, R. O., and Strausser, P., Monthly Review,
test cannot be made on a horizontal surface or at a location that
American Electroplaters Society, MRAEA, Vol 22, 1935, p. 9, and by Brenner, A.,
Proceedings, American Electroplaters Society, AEPPB, Vol 27, 1939, p. 204. does not permit rapid drainage.
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B555 − 86 (2007)
5.1.6 Drop Size—Variation in drop size may alter the 5.1.9 Composition of Coating—The dropping tests de-
penetration rate. The tip of the dropping apparatus should scribed in this document are intended for use on nominally
conform to the dimensions given in Fig. 1 and should be kept
“pure” coatings. The thickness factors listed in Section 10 are
clean.
expectedtovarywithgrossvariationsinthecompositionofthe
5.1.7 Alloy Layer—The presence of an alloy layer at the
coating, as might result from codeposition of an alloying
coating-substrate interface may obscure the end point and
component. The specific effects, on the thickness factors, of
introduce an uncertainty as to the amount of alloy included in
impurities or of inclusions from brighteners or other addition
the thickness measurement.
agents can be appreciable. Uncertainty from these sources may
5.1.8 Detection of End Point—The end point (the time at
be minimized by standardizing the test method against stan-
which the coating has been penetrated and the substrate
dards, prepared from the same type of plating solution, the
exposed) is characterized by a change in the appearance of the
thicknesses of which have been determined by other methods.
surface on which drops are falling. This is a matter of personal
judgment and may not always be clearly defined, depend
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