Standard Active Last Updated: Jun 10, 2024 Track Document
ASTM D8555-24

Standard Practice for Conducting a Coating/Lining Detachment Acoustical Sounding (Tapping) Inspection

Standard Practice for Conducting a Coating/Lining Detachment Acoustical Sounding (Tapping) Inspection D8555-24 ASTM|D8555-24|en-US Standard Practice for Conducting a Coating/Lining Detachment Acoustical Sounding (Tapping) Inspection Standard new BOS Vol. 06.02 Committee D01
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Significance and Use

5.1 Coating condition assessments are based, in large part, on visual observation of defects in or damage to the coating/ lining system. The visual observation process also identifies precursors of defects (discoloration, cracking, etc.). Such visual inspections may be augmented with destructive adhesion testing on a case-by-case basis. Acoustical sounding (tap testing) provides a non-destructive alternative to destructive testing to quickly identify areas of potential coating/lining film detachment for more intrusive examination, since poor adhesion to the substrate may not be visually evident.

5.2 Areas of suspect coating or lining adhesion revealed by the tap test may be overlooked during normal visual observation until visual indicators of failure (for example, blisters, cracks, peeling, or the presence of corrosion) become evident. Acoustical sounding can be a predictive go/no examination, in that it provides indication of a reduced bond between the coating/lining system and the substrate before disbonding becomes visually evident.

5.3 Acoustical sounding inspection is particularly useful when assessing the condition of immersion service linings that may be covered with corrosion product, staining, or other tenacious deposits that obscure small defects (Note 1). High performance coatings and linings can also visually mask disbondment and under-film corrosion due to high cohesive strength.

5.4 Although the use of acoustical sounding (tapping) to determine potential coating detachment is relatively simple, the extent of the noted detachment is subject to the inspector’s interpretation of the tonal differences in the produced sound. Likewise, areas with high levels of ambient background noise make tonal differences of the produced sounds difficult to distinguish. Furthermore, data recording must be done manually using sketches and photographs.

Note 1: For best results, the coating or lining should be cleaned prior to or in combination with acoustical sounding, as effective use of tap testing should include a concurrent visual examination.


1.1 This practice covers a method for conducting a qualitative acoustical sounding inspection by lightly tapping newly-applied and previously installed coating/lining systems with a hand-held tool to assess potential detachment from the substrate, prior to visible disbondment. A procedure is prescribed to help ensure reproducibility of the respective sounding methodology. Interpretation of the sound is qualitative and typically requires basic training, for example, the degree of tapping force to use and what to listen for, consistent with the generic type of protective coating or lining system being evaluated.

1.2 High performance coating and lining systems (independent of thickness) can be evaluated for sounding using the tap test, provided excessive tap force that may result in impact damage to otherwise acceptable, sound coatings is avoided.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 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.

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Book of Standards Volume: 06.02
Developed by Subcommittee: D01.46
Pages: 2
DOI: 10.1520/D8555-24