🔩 Assessment of the degree of flaking of paint coatings by comparison with pictorial standards — quantity of flaking on a 0–5 scale as the proportion of flaked area (from 0,1 % to 15 %), size on a 0–5 scale by the largest dimension of the exposed areas (up to 1 mm … larger than 30 mm) and depth: coat flaking from coat (a) or the whole system from the substrate (b), notation e.g. 3(S2)b, PN-EN ISO 4628-5

Materials and NDT PN-EN ISO 4628-5

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 4628-5:2023-01 (English version), in full (our translation of the Polish card text): “This document specifies a method for assessing the degree of flaking of coatings by comparison with pictorial standards. ISO 4628-1 specifies a system for designating the quantity and size of defects and the intensity of changes in appearance of coatings. It also outlines the general principles of the system. This system is intended to be used, in particular, for defects caused by ageing and weathering, and for uniform changes such as colour changes, for example yellowing.” We read the text of the standard in the ISO 4628-5:2022 preview from the cover to the bibliography — the whole document (pages iv–6); the tables were also read from the image of page 2, the photographs of the standards in Figures 1 and 2 are not described.

ACCORDING TO THE TEXT OF ISO 4628-5:2022 (whole). The standard was prepared by ISO/TC 35 “Paints and varnishes”, subcommittee SC 9, in collaboration with CEN/TC 139 (Vienna Agreement). The fourth edition replaced the third (ISO 4628-5:2016); changes according to the foreword: the title shortened to three elements, amendments to Table 2 to clarify how the size of flaking is assessed, and editorial revision. Scope (Clause 1): a method for assessing the degree of flaking of coatings by comparison with pictorial standards; the system for designating the quantity and size of defects is described in ISO 4628-1. Normative reference: ISO 13076 (lighting and procedure for visual assessment of coatings). Definition (3.1): degree of flaking — rating characterizing flaked areas of a coating in terms of quantity, size and depth. Assessment (Clause 4): the quantity of flaking is assessed according to Table 1, using as examples Figure 1 (flaking without preferential direction) or Figure 2 (flaking in a preferential direction due to anisotropy of the substrate); both figures show panels of 100 cm² to 200 cm² for quantities 1–5. Table 1 — rating of quantity: 0 — 0 %, 1 — 0,1 %, 2 — 0,3 %, 3 — 1 %, 4 — 3 %, 5 — 15 % flaked area. The average size of the individual areas exposed by flaking is assessed according to Table 2 (size of flaking — largest dimension): 0 — not visible under ×10 magnification, 1 — up to 1 mm, 2 — up to 3 mm, 3 — up to 10 mm, 4 — up to 30 mm, 5 — larger than 30 mm. Where a test area exhibits flaked areas of various sizes, the size rating quoted is that of the largest areas which are numerous enough to be typical of the area. If possible, the depth of flaking is indicated by reference to the level in the coating system where failure occurs; two main types are distinguished: coat(s) flaking from the underlying coat (type a) and the whole coating system flaking from the substrate (type b). The assessment is carried out under good illumination according to ISO 13076. Expression of results (Clause 5): the numerical ratings of quantity and size of flaking are given, where possible with the depth (type a or b), together with the approximate dimensions of the area assessed or its proportion of the total area in percent; example: quantity 3, size 2, whole system flaking from the substrate — “flaking; degree of flaking 3(S2)b”; the assessment may be amplified in words. The test report (Clause 6) contains at least: data identifying the coating, a reference to ISO 4628-5:2022, the type, size and if appropriate location of the surface examined, the result according to Clause 5, an indication of the illumination, deviations from the procedure, unusual features observed and the date of examination. Bibliography: ISO 4628-1.

COMPARISON WITH THE 2016 EDITION (ISO 4628-5:2016 preview, foreword and Clauses 1–5). Table 1 is identical; in Table 2 the 2016 edition did not have the addition “(largest dimension)” in the heading — the 2022 edition settles that the size of flaking is its largest dimension. The 2016 edition introduced (compared with ISO 4628-5:2003) the reference to ISO 13076 for illumination; the depth types in 2016 were labelled a) and b) without the word “type”.

STATUS (cards as of 02.10.2026). The card of PN-EN ISO 4628-5:2023-01 (English version) has no “Withdrawn” header — the standard is CURRENT: published 19-01-2023, 18 pages, price group J, Chemistry Sector, KT 175 Paints and Varnishes, ICS 87.040, “Introduces: EN ISO 4628-5:2022 [IDT], ISO 4628-5:2022 [IDT]”, “Replaces: PN-EN ISO 4628-5:2016-03 – English version”. PN-EN ISO 4628-5:2016-03 (English version) — withdrawn 19-01-2023 and replaced by the 2023-01 edition; it in turn replaced PN-EN ISO 4628-5:2005 (Polish version). The PKN search for “PN-EN ISO 4628-5” (02.10.2026) also shows PN-EN ISO 4628-5:2004 (English) and PN-ISO 4628-5:1999. There is no Polish version of the 2023 edition. Referenced standards: PN-EN ISO 13076:2020-03 (lighting and procedure for visual assessment of coatings; introduces ISO 13076:2019) and PN-EN ISO 4628-1:2016-03 (designation system) — both without a “Withdrawn” header (cards, read 02.10.2026).

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 02.10.2026). The number 4628-5 appears in 10 records at 9 laboratories: AB 023 (2), AB 089, AB 128, AB 163, AB 369, AB 1424, AB 1552, AB 1631, AB 1700 (1 each). In the current scopes on the PCA website (read 02.10.2026, scope issues from 16.07.2025 to 01.09.2026) the number appears at all 9: with the year “2023-01” at AB 089, AB 163, AB 1552, AB 1631 and AB 1700, with both editions “2016-03” and “2023-01” at AB 1424, without a year at AB 023, AB 128 and AB 369. No row with the number is set in bold italics (at AB 1700 the suspension concerns another part of the scope). The “Laboratories” tab searches entries BEGINNING WITH “PN-EN ISO 4628-5” and shows all 9 laboratories and 10 positions — checked with the tab query on the labcoda.pl production server on 02.10.2026; under “ISO 4628-5” — 0.

WHAT THE LABORATORIES TEST (positions in PCA). Object: paint coatings and paint systems on metal substrates, coating products for protection of elements; everywhere the number appears together with other parts of ISO 4628 (blistering, rusting, cracking, chalking, delamination around a scribe, filiform corrosion). At AB 1552 and AB 1424 next to PN-EN ISO 4628-1:2016-03. At AB 023 “flaking — visual method, also in situ”. Property: “flaking” or “assessment of degree of flaking”, visual method.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. In quantity: the 0–5 scale is the proportion of flaked area in percent, and the figures are only examples — with Figure 2 (anisotropic substrate, e.g. wood) the comparison is with a different standard than with Figure 1. In size: since the 2022 edition the LARGEST dimension of the exposed areas counts, and that of the areas typical of the area (numerous enough), not of a single largest one. In depth: type a and type b are given “where possible” — a result without the type conforms to the standard but does not say whether the substrate is exposed. In illumination: the conditions according to ISO 13076 have to be given in the report. In the reference: scopes with the year 2016-03 (AB 1424 next to 2023-01) point to a withdrawn edition — it differs in the wording of the Table 2 heading.

WHAT WE DO NOT GIVE. We have the whole text of the standard; we do not describe the photographs of the standards in Figures 1 and 2 (they are compared visually) or the lighting requirements of ISO 13076, because we have not read the text of that standard (we only know its PKN card).

Method principle

The coating surface under test is compared visually with pictorial standards (Figure 1 or 2) and the quantity of flaking is rated on a 0–5 scale as the proportion of flaked area (0; 0,1; 0,3; 1; 3; 15 %), the size on a 0–5 scale by the largest dimension of typical exposed areas (up to 1, 3, 10, 30 mm, larger than 30 mm; 0 — not visible under ×10 magnification) and the depth (a — coat from coat, b — system from substrate) under lighting according to ISO 13076; the result is noted e.g. as 3(S2)b.

Applications

• Paint coatings and paint systems on metal substrates after ageing and corrosion tests — 9 laboratories, always together with other parts of ISO 4628
• In situ assessment of coatings on structures (AB 023)
• Coatings on anisotropic substrates (e.g. wood) — flaking in a preferential direction according to Figure 2

Key parameters

Standard

Standard number

PN-EN ISO 4628-5:2023-01 (wersja angielska; EN ISO 4628-5:2022 IDT, ISO 4628-5:2022 IDT)

Title (PL)

Farby i lakiery — Ocena zniszczenia powłok — Określanie ilości i rozmiaru uszkodzeń oraz intensywności jednolitych zmian w wyglądzie — Część 5: Ocena stopnia złuszczenia

Title (EN)

Paints and varnishes — Evaluation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 5: Assessment of degree of flaking

Step-by-step procedure

1. Preparing the assessment

   Selection and description of the surface examined (type, size, location); lighting according to ISO 13076. PN-EN ISO 4628-5:2023-01 current (cards as of 02.10.2026).

2. Quantity

   Comparison with Figure 1 (without preferential direction) or Figure 2 (preferential direction) and rating 0–5 according to Table 1 (proportion of flaked area 0–15 %).

3. Size

   Rating 0–5 according to Table 2 — the largest dimension of typical (numerous enough) exposed areas; 0 if not visible under ×10 magnification.

4. Depth

   Where possible, indication of the level of failure: type a (coat from coat) or type b (system from substrate).

5. Result and report

   Notation e.g. “degree of flaking 3(S2)b”, dimensions or proportion of the area assessed, lighting, deviations, unusual features, date of examination (Clauses 5 and 6).

Required equipment and apparatus

Health and safety (OHS)

• Visual assessment without reagents; for in situ assessment — rules for work on a structure; the standard contains no safety warnings
• TECHNICAL NOTE: the size of flaking is the largest dimension of areas TYPICAL of the area, not of a single largest flake; scopes referring to the 2016-03 edition point to an edition withdrawn on 19-01-2023

Frequently asked questions