🔩 Visual assessment of degradation of a paint or varnish coating — quantity of defects (ratings 0–5), size of defects (S0–S5: from not visible under ×10 magnification to larger than 5 mm) and intensity of uniform changes in appearance, e.g. yellowing (0–5), with the proportion of the area as a percentage; expressed e.g. as “blistering 2(S2)”, assessment under lighting according to ISO 13076, PN-EN ISO 4628-1

Materials and NDT PN-EN ISO 4628-1

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 4628-1:2016-03, in full (our translation of the Polish card text): “This part of ISO 4628 defines a system for designating the quantity and size of defects and the intensity of changes in appearance of coatings and outlines the general principles of the system used in all parts of ISO 4628. This system is particularly useful for defects caused by ageing and weathering, and for uniform changes, for example yellowing. The other parts of ISO 4628 provide pictorial standards or other means for evaluating particular types of defect. As far as possible, existing evaluation methods are used as the basis. This part of ISO 4628 is also used for assessing defects not covered by the other parts of ISO 4628”. We read the text of the standard in the preview of ISO 4628-1:2016, which covers the whole document — from the cover through Clauses 1–6 to the bibliography.

ACCORDING TO THE TEXT OF ISO 4628-1:2016 (complete). The standard was prepared by ISO/TC 35/SC 9. The fourth edition replaces the third (2003); changes: a lower limit for visual assessment of defects was introduced in Table 2, a normative reference to ISO 13076 (lighting for the assessment) was added. The ISO 4628 series: Part 1 — general introduction and designation system, 2 — blistering, 3 — rusting, 4 — cracking, 5 — flaking, 6 — chalking by tape method, 7 — chalking by velvet method, 8 — delamination and corrosion around a scribe or other artificial defect, 10 — filiform corrosion. Scope (Clause 1): a system for designating the quantity and size of defects and the intensity of changes in appearance of coatings and the general principles of the system for the whole series; intended in particular for defects caused by ageing and weathering and for uniform changes, e.g. yellowing; other parts provide pictorial standards or other means of assessment; Part 1 is also used for defects not covered by other parts. Normative reference (Clause 2): ISO 13076 (lighting and procedure for visual assessment of coatings). Principles (Clause 3): a uniform numerical scale from 0 to 5 — 0 means no defects or changes, 5 — defects or changes so severe that further discrimination is not reasonable; ratings 1–4 are defined so as to give optimum discrimination over the whole range; half-steps are permitted if specified; Note 1: the quantity of small scattered defects can be assessed by a grid method according to ISO 10289; Note 2: the ISO scale may be reversed relative to other standards, e.g. in ASTM D610 (rusting) the scale runs from 10 — no change — to 1 — greatest change; in addition to the ratings, the approximate dimensions of the area concerned or its proportion of the total area as a percentage are given. Assessment (4.1): under good lighting according to ISO 13076; the first assessment is made visually, without magnification. Quantity of defects (4.2, Table 1): 0 — no detectable defects, 1 — very few (small, barely significant number), 2 — few (small but significant number), 3 — moderate number, 4 — considerable number, 5 — dense pattern of defects; whole numbers unless otherwise specified. Size of defects (4.3, Table 2), if required and meaningful: 0 — not visible under ×10 magnification, 1 — only visible under magnification up to ×10, 2 — just visible with normal corrected vision, up to 0,2 mm, 3 — clearly visible, larger than 0,2 mm up to 0,5 mm, 4 — larger than 0,5 mm up to 5 mm, 5 — larger than 5 mm, unless otherwise specified in subsequent parts of ISO 4628; with defects of various sizes, the size of the largest defects numerous enough to be typical of the area is quoted; designation Sn, e.g. S2. Intensity of changes (4.4, Table 3) — uniform changes in appearance, e.g. colour (yellowing): 0 — unchanged, 1 — very slight (just perceptible), 2 — slight (clearly perceptible), 3 — moderate (very clearly perceptible), 4 — considerable (pronounced change), 5 — very marked. Expression of results (Clause 5): type of defect, quantity and size, e.g. “blistering; degree of blistering 2(S2), i.e. quantity 2/size 2”, “flaking; degree of flaking 3(S2)”, together with the approximate dimensions of the area or its proportion as a percentage; the result may be amplified in words, e.g. “confined to edges” or “blistering of top coat down to intermediate coat”; type of change and its intensity — similarly, with dimensions or proportion of the area. Test report (Clause 6): identification of the coating, reference to ISO 4628-1, type, size and possibly location of the assessed surface, result according to Clause 5, lighting during assessment, unusual features observed, date of examination.

STATUS (cards as of 02.10.2026). The card of PN-EN ISO 4628-1:2016-03 in the English version (published 08-03-2016, 16 pages, price group H) does not carry the heading “Wycofana” (withdrawn): Chemistry Sector, KT 175 Paints and Varnishes, ICS 87.040, “Introduces: EN ISO 4628-1:2016 [IDT], ISO 4628-1:2016 [IDT]”, “Replaces: PN-EN ISO 4628-1:2005 – Polish version”. PN-EN ISO 4628-1:2005 (Polish version, published 29-04-2005, introduced ISO 4628-1:2003) — withdrawn 08-03-2016.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, load up to 17.09.2026, read on 02.10.2026). The number 4628-1 appears in 11 records at 8 laboratories: AB 023, AB 089, AB 128, AB 163, AB 369, AB 1424, AB 1552, AB 1700. In the current scopes on the PCA website (read on 02.10.2026, issues from 16.07.2025 to 01.09.2026) the number appears at all 8: with the year “2016-03” at AB 089, AB 163, AB 1424, AB 1552 and AB 1700, without a year at AB 023, AB 128 and AB 369. AB 1552 cites it four times — each time paired with Part 2, 3, 4 or 5. No row is set in bold italics (at AB 1700 the suspension concerns another part of the scope).The “Laboratories” tab searches for entries STARTING WITH “PN-EN ISO 4628-1” and shows all 8 laboratories and 12 items (one field is sometimes an entry of several standards, so there are more items than records); the entry “ISO 4628-1” gives 1 laboratory (AB 128) — checked with the tab query on the labcoda.pl production server on 02.10.2026.

WHAT THE LABORATORIES TEST (items in the PCA scopes). Organic and inorganic coatings, paint systems on metal substrates, metal and plastic products — “degradation — quantity and size of defects, visual method, also in situ” (AB 023), “evaluation of degradation of coatings” (AB 089, AB 128, AB 163, AB 1424), “evaluation of degradation of coating covering: general assessment, blistering, rusting, cracking, flaking…” (AB 369), “evaluation of degradation of coatings: blistering, rusting, cracking, flaking, filiform corrosion” after salt spray tests (AB 1700); at AB 1552 — assessment of the degree of blistering, rusting, cracking and flaking after corrosion tests. At AB 089, AB 163, AB 369, AB 1424, AB 1552 and AB 1700 together with further parts of ISO 4628 (at AB 369 up to Part 8), alongside corrosion tests (e.g. PN-EN ISO 9227, PN-EN ISO 11997-1).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Scale: ISO counts from 0 (none) to 5 (worst), while e.g. ASTM D610 counts the other way, from 10 to 1 — copying a result from one standard to the other without conversion reverses the rating. Size: the size quoted is that of the largest defects typical of the area — not of the single largest one; S2 is the limit of visibility with the naked eye (up to 0,2 mm). Magnification: the first assessment is made without magnification; the ×10 magnifier serves only to distinguish S0 from S1. Lighting: an assessment under lighting other than according to ISO 13076 is not comparable, so the lighting is entered in the report. Result: a rating alone without the proportion of the area as a percentage (or dimensions of the area) is incomplete; half-steps only when specified. Type of defect: blistering, rusting or cracking have their own pictorial standards in Parts 2–10 — Part 1 gives the framework, it does not replace those standards.

WHAT WE DO NOT GIVE. We have read the whole standard; we do not give the pictorial standards from Parts 2–10 of ISO 4628 or the grid method from ISO 10289.

Method principle

The coating is examined visually under lighting according to ISO 13076 (first without magnification) and ratings on a 0–5 scale are assigned to the quantity of defects, their size (S0–S5) or the intensity of a uniform change in appearance, stating the proportion of the assessed area as a percentage; the result is recorded as the type of defect with the quantity and size ratings, e.g. 2(S2).

Applications

• Paint coatings and paint systems on metal substrates — assessment after corrosion and ageing tests, 8 laboratories
• Assessment of defects not covered by Parts 2–10 of ISO 4628 and of uniform changes in appearance, e.g. yellowing
• In situ assessment of coatings on structures and products

Key parameters

Standard

Standard number

PN-EN ISO 4628-1:2016-03 (wersja angielska; EN ISO 4628-1:2016 IDT, ISO 4628-1:2016 IDT)

Title (PL)

Farby i lakiery — Ocena zniszczenia powłok — Określanie ilości i rozmiaru uszkodzeń oraz intensywności jednolitych zmian w wyglądzie — Część 1: Wprowadzenie ogólne i system określania

Title (EN)

Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity and size of defects, and of intensity of uniform changes in appearance — Part 1: General introduction and designation system

Step-by-step procedure

1. Preparation of the assessment

   Identification of the coating and the assessed surface (type, size, location); lighting according to ISO 13076. PN-EN ISO 4628-1:2016-03 current (cards as of 02.10.2026).

2. Visual assessment

   First assessment without magnification; identification of the type of defect or change (for types covered by Parts 2–10 — their pictorial standards).

3. Quantity and size

   Quantity rating 0–5 according to Table 1; size S0–S5 according to Table 2 for the largest defects typical of the area (×10 magnifier for S0/S1).

4. Uniform changes

   Intensity of a change in appearance, e.g. yellowing, on a 0–5 scale according to Table 3.

5. Result and report

   Recording e.g. 2(S2) with the proportion of the area in % or its dimensions, possibly a verbal description; in the report lighting, unusual features and date.

Required equipment and apparatus

Health and safety (OHS)

• Visual assessment without particular hazards; for in situ assessment on structures — rules for working at height; the standard contains no safety warnings
• SUBSTANTIVE NOTE: the ISO scale (0 = none, 5 = worst) is the reverse of e.g. ASTM D610 (10 = no change) — results must not be copied between standards without conversion

Frequently asked questions