ASTM B765-03(2023)

Standard Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings

SIGNIFICANCE AND USE
4.1 Porosity tests indicate the completeness of protection or coverage offered by the coating. When a given coating is known to be protective when properly deposited, the porosity serves as a measure of the control of the process. The effects of substrate finish and preparation, plating bath, coating process, and handling, may all affect the degree of imperfection that is measured.
Note 1: The substrate exposed by the pores may be the basis metal, an underplate, or both.  
4.2 The tests in this guide involve corrosion reactions in which the products delineate pores in coatings. Since the chemistry and properties of these products may not resemble those found in service environments, these tests are not recommended for prediction of product performance unless correlation is first established with service experience.
SCOPE
1.1 This guide describes some of the available standard methods for the detection, identification, and measurement of porosity and gross defects in electrodeposited and related metallic coatings and provides some laboratory-type evaluations and acceptances. Some applications of the test methods are tabulated in Table 1 and Table 2.    
1.2 This guide does not apply to coatings that are produced by thermal spraying, ion bombardment, sputtering, and other similar techniques where the coatings are applied in the form of discrete particles impacting on the substrate.  
1.3 This guide does not apply to beneficial or controlled porosity, such as that present in microdiscontinuous chromium coatings.  
1.4 Porosity test results (including those for gross defects) occur as chemical reaction end products. Some occur in situ, others on paper, or in a gel coating. Observations are made that are consistent with the test method, the items being tested, and the requirements of the purchaser. These may be visual inspection (unaided eye) or by 10× magnification (microscope). Other methods may involve enlarged photographs or photomicrographs.  
1.5 The test methods are only summarized. The individual standards must be referred to for the instructions on how to perform the tests.  
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.7 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.  
1.8 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 B765-03(2018) - Standard Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
• Effective Date: 01-Nov-2023
• Refers: ASTM B734-97(2023) - Standard Specification for Electrodeposited Copper for Engineering Uses
• Effective Date: 01-Nov-2023
• Refers: ASTM B650-23 - Standard Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates
• Effective Date: 01-Nov-2023
• Refers: ASTM B650-95(2023) - Standard Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates
• Effective Date: 01-May-2023
• Refers: ASTM B734-97(2018) - Standard Specification for Electrodeposited Copper for Engineering Uses
• Effective Date: 01-Jun-2018
• Referred By: ASTM B689-97(2023) - Standard Specification for Electroplated Engineering Nickel Coatings
• Effective Date: 01-Nov-2023
• Referred By: ASTM B605-22 - Standard Specification for Electrodeposited Coatings of Tin-Nickel Alloy
• Effective Date: 01-Nov-2023
• Referred By: ASTM B809-95(2018) - Standard Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers-of-Sulfur”)
• Effective Date: 01-Nov-2023
• Referred By: ASTM B545-22 - Standard Specification for Electrodeposited Coatings of Tin
• Effective Date: 01-Nov-2023
• Referred By: ASTM B799-95(2020) - Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
• Effective Date: 01-Nov-2023
• Referred By: ASTM B866-95(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by Polysulfide Immersion
• Effective Date: 01-Nov-2023
• Referred By: ASTM B877-96(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by the Phosphomolybdic Acid (PMA) Method
• Effective Date: 01-Nov-2023
• Referred By: ASTM B920-16(2022) - Standard Practice for Porosity in Gold and Palladium Alloy Coatings on Metal Substrates by Vapors of Sodium Hypochlorite Solution
• Effective Date: 01-Nov-2023
• Referred By: ASTM B488-18 - Standard Specification for Electrodeposited Coatings of Gold for Engineering Uses
• Effective Date: 01-Nov-2023
• Referred By: ASTM B798-95(2020) - Standard Test Method for Porosity in Gold or Palladium Coatings on Metal Substrates by Gel-Bulk Electrography
• Effective Date: 01-Nov-2023

Overview

ASTM B765-03(2023), "Standard Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings," provides a comprehensive overview of standard methods to detect, identify, and measure porosity and gross defects in electrodeposited and similar metallic coatings. Developed by ASTM International, this guide outlines laboratory procedures suitable for a variety of metals and coatings, helping stakeholders ensure the integrity, protection, and reliability of coated products. This standard is recognized internationally for its role in quality assurance and control within the electroplating and surface engineering industries.

Key Topics

• Porosity Testing: The standard describes multiple methods for porosity testing, which reveal holes, cracks, or defects that expose the underlying substrate. Porosity levels are an important measure of the quality and protection provided by metallic coatings.
• Gross Defect Detection: Gross defects-such as mechanical damage, wear, or significant coating discontinuities-are outlined separately from routine porosity, highlighting tests for more severe failures.
• Test Overview: Typical methods include chemical reaction-based processes where corrosion products make pore sites visible. Visual or microscopic observations, or photographic techniques, are part of these evaluations.
• Intrinsic vs. Gross Defects: The document differentiates between intrinsic porosity (small, routine imperfections from deposition processes) and gross defects (such as mechanical damage or large, as-plated pores).
• Applicability: The guide covers coatings like gold, silver, nickel, tin, and their alloys over a variety of substrates such as copper, iron, steel, and aluminum. It does not apply to thermal spray or physical vapor deposition coatings, or controlled/beneficially porous coatings.
• Test Limitations: These laboratory porosity tests do not always simulate real-world service environments; results should be correlated with actual performance where necessary.

Applications

ASTM B765 is critical for:

• Quality Assurance: Ensuring electrodeposited and related metallic coatings consistently provide full coverage and protection, verified through porosity and gross defect assessments.
• Process Control: Indicating the degree to which substrate preparation, plating baths, and handling influence coating integrity.
• Product Evaluation: Practical for manufacturers and purchasers to assess and compare the suitability and durability of metallic coatings across multiple applications, including electronics, automotive components, machinery, and decorative finishes.
• Inspection: Facilitating visual and microscopic inspection routines-especially important during development, incoming inspection, and pre-shipment quality audits.
• Failure Analysis: Detecting and quantifying coating defects that may lead to product failures, supporting root cause analysis and corrective actions.

Related Standards

Several ASTM standards are referenced within ASTM B765 and provide detailed procedures for specific tests, definitions, and quality criteria, including:

• ASTM B276 - Test Method for Apparent Porosity in Cemented Carbides
• ASTM B374 - Terminology Relating to Electroplating
• ASTM B537 - Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure
• ASTM B545 - Specification for Electrodeposited Coatings of Tin
• ASTM B605 - Specification for Electrodeposited Coatings of Tin-Nickel Alloy
• ASTM B650 - Specification for Electrodeposited Engineering Chromium Coatings on Ferrous Substrates
• ASTM B689 - Specification for Electroplated Engineering Nickel Coatings
• ASTM B733 - Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal
• ASTM B735 - Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor
• ASTM B798/B799 - Test Methods for Porosity in Gold, Palladium, or Silver Coatings
• ASTM B809 - Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers-of-Sulfur”)
• ASTM B866/B877 - Test Methods for Gross Defects and Mechanical Damage in Metallic Coatings

By referring to ASTM B765 and these related standards, organizations can establish validated, consistent quality control practices for electrodeposited and related metallic coatings, supporting both internal requirements and international trade.

Keywords: electrodeposits, porosity testing, gross defect detection, metallic coatings, quality assurance, electroplating standards, ASTM B765, surface engineering.

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: B765 − 03 (Reapproved 2023)
Standard Guide for
Selection of Porosity and Gross Defect Tests for
Electrodeposits and Related Metallic Coatings
This standard is issued under the fixed designation B765; 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 1.8 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This guide describes some of the available standard
ization established in the Decision on Principles for the
methods for the detection, identification, and measurement of
Development of International Standards, Guides and Recom-
porosity and gross defects in electrodeposited and related
mendations issued by the World Trade Organization Technical
metallic coatings and provides some laboratory-type evalua-
Barriers to Trade (TBT) Committee.
tions and acceptances. Some applications of the test methods
are tabulated in Table 1 and Table 2.
2. Referenced Documents
1.2 This guide does not apply to coatings that are produced
2.1 ASTM Standards:
by thermal spraying, ion bombardment, sputtering, and other
B276 Test Method for Apparent Porosity in Cemented Car-
similar techniques where the coatings are applied in the form of
bides
discrete particles impacting on the substrate.
B374 Terminology Relating to Electroplating
1.3 This guide does not apply to beneficial or controlled
B537 Practice for Rating of Electroplated Panels Subjected
porosity, such as that present in microdiscontinuous chromium to Atmospheric Exposure
coatings.
B542 Terminology Relating to Electrical Contacts and Their
Use
1.4 Porosity test results (including those for gross defects)
B545 Specification for Electrodeposited Coatings of Tin
occur as chemical reaction end products. Some occur in situ,
B605 Specification for Electrodeposited Coatings of Tin-
others on paper, or in a gel coating. Observations are made that
Nickel Alloy
are consistent with the test method, the items being tested, and
B650 Specification for Electrodeposited Engineering Chro-
the requirements of the purchaser. These may be visual
mium Coatings on Ferrous Substrates
inspection (unaided eye) or by 10× magnification (micro-
B689 Specification for Electroplated Engineering Nickel
scope). Other methods may involve enlarged photographs or
Coatings
photomicrographs.
B733 Specification for Autocatalytic (Electroless) Nickel-
1.5 The test methods are only summarized. The individual
Phosphorus Coatings on Metal
standards must be referred to for the instructions on how to
B734 Specification for Electrodeposited Copper for Engi-
perform the tests.
neering Uses
B735 Test Method for Porosity in Gold Coatings on Metal
1.6 The values stated in SI units are to be regarded as
Substrates by Nitric Acid Vapor
standard. The values given in parentheses are for information
B741 Test Method for Porosity In Gold Coatings On Metal
only.
Substrates By Paper Electrography (Withdrawn 2005)
1.7 This standard does not purport to address all of the
B798 Test Method for Porosity in Gold or Palladium Coat-
safety concerns, if any, associated with its use. It is the
ings on Metal Substrates by Gel-Bulk Electrography
responsibility of the user of this standard to establish appro-
B799 Test Method for Porosity in Gold and Palladium
priate safety, health, and environmental practices and deter-
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
mine the applicability of regulatory limitations prior to use.
B809 Test Method for Porosity in Metallic Coatings by
1 2
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on Test contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Methods. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2023. Published November 2023. Originally the ASTM website.
approved in 1986. Last previous edition approved in 2018 as B765 – 93 (2018). The last approved version of this historical standard is referenced on
DOI: 10.1520/B0765-03R23. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B765 − 03 (2023)
TABLE 1 Applications of Standard Porosity Tests to Metallic Coatings (Section 6)
A
Substrate Metal Gold Silver Nickel Tin-Nickel Tin Tin-Lead Copper Palladium Chromium
B
Copper and Copper 6.1 , 6.2, 6.3A 6.4 6.4 6.4 6.4 . 6.2, 6.3A, 6.4, .
6.4, 6.5
Alloys 6.5
B
Nickel 6.1 , 6.2, 6.5 6.3A . . . . . 6.2, 6.3A, 6.5 .
Iron or Steel 6.6 . 6.6 6.3B, 6.6 6.3B, 6.6 6.3B, 6.6 6.6 . 6.6
Silver 6.4 . 6.4 6.4 6.4 6.4 . 6.4 .
A
The substrate may be the basis metal, an underplate, or both (see Note 1).
B
Thickness restrictions may apply.
TABLE 2 Applications of Tests for Gross Defects and Mechanical Damage (Section 7)
A
Substrate Metal Gold Nickel Tin-Nickel Tin Tin-Lead Palladium Silver
Copper and Copper 7.3, 7.5 7.3, 7.4 7.3 7.3 7.3 7.3, 7.5 7.5
Alloys
Nickel 7.5 . . . . 7.5 7.5
Iron or Steel 7.1 7.1 7.1 7.1 7.1 7.1 .
Aluminum . 7.2 . . . . .
A
The substrate may be the basis metal, an underplate, or both (see Note 1).
Humid Sulfur Vapor (“Flowers-of-Sulfur”) 5. Applications
B866 Test Method for Gross Defects and Mechanical Dam-
5.1 From the viewpoint of both porosity testing and func-
age in Metallic Coatings by Polysulfide Immersion
tional significance, it is useful to divide porosity into two broad
B877 Test Method for Gross Defects and Mechanical Dam- 4,5
categories, namely intrinsic porosity and gross defects.
age in Metallic Coatings by the Phosphomolybdic Acid
5.1.1 Intrinsic or normal porosity is due primarily to small
(PMA) Method
deviations from ideal plating and surface preparation condi-
tions. As such, it will be present to some degree in all
3. Terminology
commercial thin platings and will generally follow an inverse
3.1 Definitions—Many terms used in this guide are defined relationship with thickness. In addition, scanning electron
microscope (SEM) studies have shown that the diameter of
in Terminology B374 or B542.
such pores at the plating surface is of the order of micrometers,
3.2 Definitions of Terms Specific to This Standard:
so that only small areas of underlying metal are exposed to the
3.2.1 porosity—for the purpose of this guide, porosity in a
environment.
coating is defined as any hole, crack, or other defect that
5.1.2 Gross defects, on the other hand, would result in
exposes the underlying metal to the environment. Differences
comparatively large areas of exposed basis metal or underplat-
between the major types of porosity are described in Section 5.
ing. Examples of such defects are mechanical damage to the
3.2.2 underplate—a metallic coating layer between the basis
coating through mishandling or wear. Gross defects can also be
metal and the topmost metallic coating. The thickness of an
found in undamaged coatings in the form of networks of
underplating is usually greater than 1 μm, in contrast to a strike
microcracks and as large as-plated pores—with diameters an
or flash, which are usually thinner.
order of magnitude (or more) greater than intrinsic porosity.
Such gross defects indicate such serious deviations from
4. Significance and Use
acceptable coating practice as dirty substrates and contami-
nated or out-of-balance baths.
4.1 Porosity tests indicate the completeness of protection or
coverage offered by the coating. When a given coating is
5.2 Intrinsic porosity and most types of gross defects are too
known to be protective when properly deposited, the porosity
small to be seen except at magnifications so high that a realistic
serves as a measure of the control of the process. The effects of
assessment of the overall coating surface in the functional areas
substrate finish and preparation, plating bath, coating process,
of the part cannot be made. Instead, the presence and severity
and handling, may all affect the degree of imperfection that is
of the porosity is normally determined by some type of
measured.
pore-corrosion test that will magnify the pore sites by produc-
ing visible reaction products in and around the pores or cracks.
NOTE 1—The substrate exposed by the pores may be the basis metal, an
Tests for gross defects (Section 7), and especially for mechani-
underplate, or both.
cal damage and wear, are designed to be less severe. Such tests,
4.2 The tests in this guide involve corrosion reactions in
which the products delineate pores in coatings. Since the
Baker, R. G., Holden, C. A., and Mendizza, A., Proceedings of the American
chemistry and properties of these products may not resemble
Electroplaters Society, Vol 50, 1963, p. 61.
those found in service environments, these tests are not
Krumbein, S. J., “The ASTM Approach to Porosity Testing,” Proc. 1991
recommended for prediction of product performance unless
International Technical Conf. of the American Electroplaters and Surface Finishers
correlation is first established with service experience. Soc., (SUR/FIN ’91), Toronto, 1991, pp. 527–536.
B765 − 03 (2023)
however, may not detect a sizeable portion of the smaller 6.3.1.2 Variation B applies to tin and its alloys over iron or
(intrinsic) pores in a coating. On the other hand, standard tests steel (Appendixes of Specification B545 and Specification
for intrinsic porosity (Section 6) will easily reveal the presence B605).
of gross defects as well. 6.3.2 Summary of Test Method—The test specimens are
suspended over sulfur-oxide acidic solutions in a sealed cham-
5.3 Porosity tests are generally destructive in n
...