🔩 Assessment of the degree of delamination and corrosion around a scribe or other artificial defect (e.g. circular) on a coated panel after exposure to a corrosive environment (salt spray, immersion in seawater, natural environment) — removal of loose coating with a knife, width measured with a ruler to 0,5 mm at at least six points, d = (d1 − w)/2 and c = (wc − w)/2, area formulae for non-uniform damage, at least three panels, PN-EN ISO 4628-8

Materials and NDT PN-EN ISO 4628-8

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 4628-8:2013-05 (Polish version), in full (our translation of the Polish card text): “This part of ISO 4628 specifies a method for assessing the delamination and corrosion around a scribe or other artificial defect on a coated panel or other coated test specimen caused by a corrosive environment. This part of ISO 4628 does not cover the assessment of pitting corrosion or the depth of pits. NOTE 1 Examples of corrosive environments are artificial atmospheres such as salt spray, used in the test method specified in ISO 9227, and immersion in seawater, used in the test method specified in ISO 15711. Natural environments can also be used. NOTE 2 When determining delamination and corrosion, the degree of other defects can also be determined by the following methods: blistering in accordance with ISO 4628-2; rusting in accordance with ISO 4628-3; cracking in accordance with ISO 4628-4; flaking in accordance with ISO 4628-5; filiform corrosion in accordance with ISO 4628-10.” We read the text of the standard in the preview of ISO 4628-8:2012 from the cover to formula (7) in clause 6.2 (page 5); we do not have formula (8), the pictorial standards of Figure 2 or the test report.

ACCORDING TO THE TEXT OF ISO 4628-8:2012 (foreword, introduction, Clauses 1–6.2 up to formula 7). The standard was prepared by ISO/TC 35/SC 9. The second edition replaces the first (2005); changes: precedence of measurement and calculation over pictorial standards, and introduction of artificial defects of a shape other than a linear scribe. Introduction: after exposure of a scribed panel to a corrosive environment, delamination, corrosion or both may occur — they are assessed separately; besides the procedure of the standard, optical image analysis may be used. Normative reference: ISO 3270 (conditioning atmospheres). Definitions (Clause 3): coating defect; artificial defect — a defect introduced intentionally to expose the metal substrate before exposure; circular defect; corroded area — around the defect, where the substrate has been attacked by corrosion; delaminated area — where loss of adhesion of the coating to the substrate or to the underlying coat has occurred; scribe — an intentional linear defect. Principle (Clause 4): delamination is assessed immediately after the end of the test, right after removing the panel from the preceding conditioning environment, or after conditioning for a specified time; corrosion — right after removal or after removing the coating; both degrees are determined by measurement and calculation. Procedure (Clause 5): delamination is assessed immediately after removing the panels, unless otherwise agreed — then after further conditioning, during which adhesion may recover; corrosion — on the coated panel or after stripping the coating (after assessing delamination); at least three panels, unless otherwise agreed. Delamination immediately after the test (5.2.1): the panel is rinsed with tap water before the coating dries, the water may be blown off with compressed air, and the panel is examined; the loose coating is removed with a knife blade held at an angle, at the coating/substrate interface — the delamination boundary is where the coating becomes firmly adherent, so adhesion must also be assessed beyond the boundary; if there is no boundary and the coating comes off easily up to the panel edge — this is recorded in the report; instead of a knife, compressed air or tape can be used; the total width of delamination is measured with a ruler to 0,5 mm at at least six points evenly along the scribe or around the defect (Figure 1, measurements a–f), ignoring delamination beyond the start and end of the scribe; more accurately — with a magnifier with a scale; more points if required by the test standard (recorded in the report); for a scribe shorter than 50 mm fewer measurements, at least 6 mm apart. After conditioning (5.2.2): assessment as in 5.2.1 after 24 h at (23 ± 2) °C and (50 ± 5) % relative humidity according to ISO 3270. Corrosion (5.3.1): rinsing, removal of loose coating with a knife or a suitable stripper, compressed air or tape, measurement of the corrosion width at at least six points to 0,5 mm; the corrosion zone is usually visible as a difference in colour. On panels with the coating removed (5.3.2): the coating is stripped with a stripper that does not aggravate corrosion or mechanically, the panel is rinsed quickly, dried with compressed air and immediately covered with a clear lacquer (e.g. aerosol), then measured as in 5.3.1. Pictorial standards (5.4): assessment by measurement is preferred; the pictorial standards of Figure 2 (based on the ISO 4628-1 system) only by agreement between the parties. Calculations (Clause 6): mean width of delamination d1 = (a+b+c+d+e+f)/6 to 0,5 mm; delamination d = (d1 − w)/2, where w — width of the original scribe or defect; for non-uniform delamination — more points or an area formula: for a scribe d = (Ad − Al)/2 × 1/l, for a circular defect d = (1/√π)(√Ad − √Al), where Ad — delaminated area including the scribe, Al — area of the scribe, l — length of the scribe; the area is determined e.g. by counting squares of transparent graph paper; the result — mean width to 0,5 mm; corrosion analogously: wc = (a+…+f)/6, c = (wc − w)/2, for non-uniform corrosion — formula (7) for a scribe; this is where the part we read ends.

STATUS (cards as of 02.10.2026). The cards of PN-EN ISO 4628-8:2013-05 in the English version (published 30-05-2013, 20 pages, price group K) and the Polish version (published 11-12-2015, 16 pages, price group H) do not carry the heading “Wycofana” (withdrawn): Chemistry Sector, KT 175 Paints and Varnishes, ICS 87.040, “Introduces: EN ISO 4628-8:2012 [IDT], ISO 4628-8:2012 [IDT]”, “Replaces: PN-EN ISO 4628-8:2006 – Polish version”. PN-EN ISO 4628-8:2006 (Polish version, introduced ISO 4628-8:2005; title without “other artificial defect”) — withdrawn 30-05-2013 and replaced by the 2013-05 edition in the English, Polish and German versions. The PKN search for “PN-EN ISO 4628-8” (02.10.2026) also shows PN-EN ISO 4628-8:2005 (English).

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 4628-8 appears in 8 records at 8 laboratories: AB 023, AB 089, AB 128, AB 163, AB 369, AB 1424, AB 1631, AB 1700. In the current scopes on the PCA website (read on 02.10.2026, issues from 16.07.2025 to 24.06.2026) the number appears at all 8: with the year “2013-05” at AB 089, AB 163, AB 1424, AB 1631 and AB 1700, without a year at AB 023, AB 128 and AB 369. 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 4628-8” and shows all 8 laboratories and 8 items — checked with the tab query on the labcoda.pl production server on 02.10.2026.

WHAT THE LABORATORIES TEST (items in the PCA scopes). Coatings, paint systems on metal substrates, organic and inorganic coatings, metal products — “delamination and corrosion around a scribe” (AB 023, AB 128), “assessment of the degree of delamination and corrosion around a scribe or other artificial defect” (AB 089, AB 1424, AB 1631), visual method (AB 163); usually in the same group as the other parts of ISO 4628 (blistering, rusting, cracking, flaking, chalking) and corrosion tests (e.g. continuous condensation according to PN-EN ISO 6270-1 at AB 1424).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. Delamination: the boundary is where the coating becomes firmly adherent — whoever stops scraping at the first resistance underestimates the result; adhesion must be checked beyond the boundary. Timing: delamination is assessed right after removing the panel, before the coating dries; after conditioning (24 h) adhesion may recover and the result decreases. Calculation: d and c are the width on ONE side of the scribe — the scribe width is subtracted from the mean width and divided by 2; reporting d1 alone doubles the result. Ends: delamination and corrosion beyond the start and end of the scribe are ignored. Pictorial standards: only by agreement — measurement takes precedence. Number of panels: at least three, unless otherwise agreed. Scope: pitting corrosion and pit depth are outside the standard.

WHAT WE DO NOT GIVE. We do not have formula (8) (corrosion around a circular defect), the pictorial standards of Figure 2 or the test report — so we do not give pictorial ratings or the required content of the report.

Method principle

After exposure of a panel with a scribe or other artificial defect to a corrosive environment, the loose coating is removed and the width of the delaminated and corroded zone is measured with a ruler (to 0,5 mm) at at least six points; the scribe width is subtracted from the mean width and divided by 2 (d, c), and for non-uniform damage the result is calculated from areas.

Applications

• Paint systems on metal substrates after corrosion tests (salt spray, condensation, immersion) — 8 laboratories
• Organic and inorganic coatings on metal products — assessment of protection when the coating is damaged
• Comparisons of coating systems (delamination and corrosion separately)

Key parameters

Standard

Standard number

PN-EN ISO 4628-8:2013-05 (wersje angielska, polska i niemiecka; EN ISO 4628-8:2012 IDT, ISO 4628-8:2012 IDT)

Title (PL)

Farby i lakiery — Ocena zniszczenia powłok — Określanie ilości i rozmiaru uszkodzeń oraz intensywności jednolitych zmian w wyglądzie — Część 8: Ocena stopnia odwarstwienia i skorodowania wokół rysy lub innego sztucznego uszkodzenia

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 8: Assessment of degree of delamination and corrosion around a scribe or other artificial defect

Step-by-step procedure

1. Removal and rinsing

   Right after exposure the panel is rinsed with tap water before the coating dries and examined; at least three panels. PN-EN ISO 4628-8:2013-05 current (cards as of 02.10.2026).

2. Removal of loose coating

   With a knife at an angle at the coating/substrate interface (or compressed air, tape) up to where the coating is firmly adherent; no boundary — recorded in the report.

3. Measurement of delamination

   Total width at at least six points to 0,5 mm (magnifier if needed), ignoring zones beyond the scribe ends; possibly after conditioning for 24 h.

4. Measurement of corrosion

   On the coated panel (difference in colour) or after stripping the coating, rinsing, drying and protecting with lacquer — width at at least six points.

5. Calculation

   d = (d1 − w)/2 and c = (wc − w)/2 to 0,5 mm; for non-uniform damage area formulae (3), (4), (7); pictorial standards only by agreement.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Working with a knife (scraping off coating) and compressed air — gloves, goggles; coating strippers and aerosol lacquers — ventilation; the part of the standard we read contains no safety warnings
• SUBSTANTIVE NOTE: d and c are widths on one side of the scribe, after subtracting the scribe width; delamination is assessed before the coating dries — after conditioning adhesion may recover

Frequently asked questions