ASTM B555-86(2023)

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 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.

General Information

• Status: Published
• Publication Date: 31-Oct-2023
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.10 - Test Methods

Relations

• Replaces: ASTM B555-86(2018) - Standard Guide for Measurement of Electrodeposited Metallic Coating Thicknesses by Dropping Test
• Effective Date: 01-Nov-2023

Overview

ASTM B555-86(2023) is an international standard guide developed by ASTM International for measuring the thickness of electrodeposited metallic coatings using the dropping test method. This technique offers an approximate determination of coating thickness for metals such as zinc, cadmium, copper, and tin, which is often critical to the functional performance and durability of plated components. The standard outlines the significance, limitations, and factors affecting the accuracy of results, and is intended for situations where a high level of precision is not required.

Key Topics

• Electrodeposited Coatings Measurement
  • Focuses on zinc, cadmium, copper, and tin electrodeposited layers.
• Dropping Test Method
  • Involves dropping a controlled rate of corrosive solution onto a metal-coated specimen and timing the breakthrough to the base metal.
• Approximate Accuracy
  • Suitable when the highest accuracy is not essential; for more precise results, refer to methods B487, B499, B504, and B568.
• Factors Influencing Results
  • Cleanliness of sample surface
  • Concentration and temperature of the test solution
  • Dropping rate and apparatus consistency
  • Coating composition and presence of alloy layers

Applications

• Quality Control in Electroplating
  • Provides a convenient field or laboratory method for quick assessment of metallic coating thickness, particularly useful during production or process tuning.
• Verification of Electroplated Components
  • Applies to industries such as automotive, electronics, aerospace, and general manufacturing where zinc, cadmium, copper, or tin coatings are commonly specified for corrosion protection.
• Rapid Testing and Screening
  • Facilitates a fast indication of coating thickness when detailed laboratory analysis is unavailable or not justified, aiding in process monitoring and batch verification.
• Process Development and Troubleshooting
  • Helps identify variations in plating processes by highlighting gross deviations in coating thickness across samples.

Related Standards

• ASTM B487 - Microscopical Examination of Metal and Oxide Coating Thickness
• ASTM B499 - Magnetic Method for Nonmagnetic Coatings on Magnetic Basis Metals
• ASTM B504 - Coulometric Method for Metallic Coating Thickness
• ASTM B568 - X-Ray Spectrometry for Coating Thickness Measurement
• ASTM D1193 - Specification for Reagent Water (used in test solution preparation)

Practical Value

• Cost-effective and Accessible
  • The dropping test offers a simple, equipment-light alternative to more advanced and expensive measurement techniques, making it practical for many facilities.
• Versatility
  • Useful with various electrodeposited metal coatings, as long as users are aware of its approximate nature and follow recommended procedures for cleaning and solution preparation.
• Compliance and Standardization
  • Developed in alignment with World Trade Organization (WTO) Technical Barriers to Trade (TBT) principles, ASTM B555-86(2023) supports international harmonization.

Conclusion

ASTM B555-86(2023) is an important guide for industries that require routine, approximate measurements of electrodeposited metallic coating thickness. While it cannot replace more accurate laboratory techniques for critical applications, it serves as a reliable tool for rapid assessment and quality control where speed and convenience are prioritized. Proper attention to factors such as surface cleanliness, solution properties, and consistent procedure is vital for obtaining meaningful results. For further accuracy, this guide should be used in conjunction with standardized comparison specimens or alternative measurement standards.

Standards Content (Sample)

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.
Designation: B555 − 86 (Reapproved 2023)
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
1.1 This guide covers the use of the dropping test to 3.1 A dropping test consists of applying dropwise a corro-
measure the thickness of electrodeposited zinc, cadmium, sive solution, at a constant rate, to the electroplated surface,
copper, and tin coatings. and measuring the time required to penetrate the coating and
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
1.2 This standard does not purport to address all of the
4.1 The thickness of a metal coating is often critical to its
safety concerns, if any, associated with its use. It is the
performance.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4.2 This procedure is useful for an approximate determina-
mine the applicability of regulatory limitations prior to use.
tion when the best possible accuracy is not required. For more
1.3 This international standard was developed in accor-
reliable determinations, the following methods are available:
dance with internationally recognized principles on standard-
Test Methods B487, B499, B504, and B568.
ization established in the Decision on Principles for the
4.3 This test assumes that the rate of dissolution of the
Development of International Standards, Guides and Recom-
coating by the corrosive reagent under the specified conditions
mendations issued by the World Trade Organization Technical
is always the same.
Barriers to Trade (TBT) Committee.
5. Factors Affecting the Accuracy
2. Referenced Documents
5.1 The following factors will affect the accuracy of a
2.1 ASTM Standards:
coating thickness measurement made by this method:
B487 Test Method for Measurement of Metal and Oxide
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 Nov. 1, 2023. Published November 2023. Originally
approved in 1971. Last previous edition approved in 2018 as B555 – 86 (2018).
tion of the dropping rate. The thickness factors given in Section
DOI: 10.1520/B0555-86R23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. 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 (2023)
10 are for a dropping rate of 100 drops/min and will remain “pure” coatings. The thickness factors listed in Section 10 are
valid for the range of 95 drops ⁄min to 105 drops ⁄min. expected to vary with gross variations in the composition of the
5.1.5 Solution Drainage—The thickness factors given in coating, as might result from codeposition of an alloying
Section 10 are valid only if the test solution is rapidly drained component. The specific effects, on the thickness factors, of
off, as from a flat surface inclined 45° from the horizontal. The impurities or of inclusions from brighteners or other addition
test cannot be made on a horizontal surface or at a location that agents can be appreciable. Uncertainty from these sources may
does not permit rapid drainage. be minimized by standardizing the test method against
5.1.6 Drop Size—Variation in drop size may alter the standards, prepared from the same type of plating solution, the
penetration rate. The tip of the dropping apparatus should thicknesses of which have been determined by other methods.
conform to the dimensions given in Fig. 1 and should be kept
6. Apparatus
clean.
6.1 Fig. 1 illustrates one form of apparatus used for drop-
5.1.7 Alloy Layer—The presence of an alloy layer at the
ping tests. Equivalent apparatus are commercially available, as
coating-substrate interface may obscure the end point and
is a solenoid operated unit with a digital readout.
introduce an uncertainty as to the amount of alloy included in
the thickness measurement.
7. Rea
...