| Scope / Applicability | Applies to non-electrolytically applied zinc-flake coating systems for steel fasteners (bolts, screws, studs, nuts, washers, pins, clips, etc.). Not for mechanically applied zinc coatings. | Applies to non-electrolytically applied zinc-flake coatings on iron/steel components excluding threaded fasteners. Notes on curing temperature vs service temperature. |
| Purpose / Focus | Fastener-specific requirements: torque/clamp force, ductility for assembly, tests relevant to fasteners; IHE risk management for high-strength fasteners. | General corrosion protection requirements for components; process guidance (immersion vs spray), minimum local thickness requirements and sampling/adhesion tests. |
| Terminology (yc / nc, flZn etc.) | Uses flZn (base coat), flZnL (integral lubricant). yc = coating with Cr(VI) (chromated); nc = Cr(VI)-free. TL/Tn indicate top coat lubricant presence. | Defines fl = flake, i = immersion, p = pneumatic/spray; yc = coating with chromate; nc = coating without chromate. Topcoats T1-T4 defined. |
| Designation format (order / label) | Coating designation is appended to fastener designation using Table 3 order fields: **base coat / yc | nc / topcoat / lubricant / NSS hours / other** (examples provided). Labelling minimum: flZn, yc or nc, and NSS hours. |
| Coating processes allowed / notes | Dip-spin or spray; bulk or rack coating; cure temperatures can be up to 320 °C (must not exceed tempering of quenched & tempered fasteners). Emphasis on process selection for fastener geometry. | Immersion (cold) or pneumatic/electrostatic spraying (selective). Immersion gives full coverage; curing typically >180 °C for 15-60 min. |
| Pre-treatment & IHE (hydrogen embrittlement) | Specific guidance to avoid internal hydrogen embrittlement (IHE): mechanical cleaning preferred; acid pickling allowed only with inhibitors and limited exposure; phosphating permitted as alternative; cathodic cleaning forbidden. Special rules for hardness >390 HV / property class 12.9+. | Recommends mechanical cleaning for Rm ≥ 1 000 MPa to avoid hydrogen absorption; requires stress relief before coating when tensile stresses exist for Rm ≥ 1 000 MPa (ISO 9587). Warns aluminium flakes continuous bond can raise IHE risk for Rm >1 800 MPa. |
| Thickness philosophy | Reference thickness / performance (NSS hours) are used – ISO gives coating system designation based on salt spray duration (e.g., /480h), not only thickness. Thickness/weight tests listed for in-process/inquiry. Microscopic method ISO 1463 used in dispute. | Minimum local thickness (µm) is mandatory and linked to salt spray performance in Table 1. Designations include explicit thickness numbers (e.g., iflZn4). Table 1 gives required µm for chromated vs non-chromated systems. |
| Salt spray / Corrosion testing (NSS) | Uses ISO 9227 NSS; corrosion resistance expressed as required NSS hours (no red rust). NSS hours used in designations (e.g., flZn/nc/720h). ISO also allows SO₂ test if specifically required. | Uses EN ISO 9227 (NSS). Table 1 defines minimum µm for a required NSS duration and differentiates with chromate (flZn yc) and without chromate (flZn nc) with different µm values per hour. |
| Table -Thickness vs NSS (from EN 13858 Table 1) | ISO uses NSS hours instead of fixed minimum µm in designation – (see ISO examples). For exact µm → convert using ISO methods if required (ISO has thickness/weight methods). | EN 13858 Table 1 (minimum local thickness µm): 240 h → chromated 4 µm / non-chromated 6 µm480 h → 5 / 8 µm720 h → 8 / 10 µm960 h → 9 / 12 µm. (Table includes mass-to-thickness conversion factors). |
| Adhesion / Cohesion tests | Tape adhesion test specified: 25 mm tape with peel force (7 ±1 N) – coating shall not peel from base metal; small coating left on tape acceptable. Adhesion/cohesion test included in in-process control. | Adhesion methods: EN ISO 2819 or Annex B (scoring/tape/bend/burnish). Acceptance: no peeling from substrate; cohesive failure within coating is acceptable. |
| Ductility / Mechanical behavior | Ductility requirements for fasteners: coating must be compatible with elastic deformation during assembly (tightening, bending). Specific ductility tests to be agreed between purchaser & supplier. | Not fastener-specific; EN requires appearance and coverage but does not contain the same ductility/assembly tests as ISO. |
| Torque / Clamp force / Friction | ISO includes torque/clamp force relationship tests for fasteners (ISO 16047 referenced). Coating designation can include coefficient of friction C and torque requirements. | EN mentions supplementary coatings to change friction properties but does not include ISO’s fastener torque/clamp requirement structure. Purchaser may request performance tests for lubricated coatings. |
| Cathodic protection (scratch test) | ISO defines a method: scratch to base metal and after 72 h NSS there shall be no red rust in scratched area (sacrificial cathodic protection test). | EN describes corrosion protection principles and behavior but does not give ISO’s fastener-specific scratch/cathodic test. Purchaser can request accelerated corrosion tests. |
| Curing temperature / effects | Curing temperatures may be up to 320 °C for some systems; must not exceed tempering temp of quenched & tempered fasteners – curing can affect fatigue/temper. ISO warns about effects on fasteners. | Typical curing >180 °C for 15-60 min; the standard warns components should not be used at temperatures higher than curing temp unless agreed. |
| Sampling / Lot testing | Tests mandatory per lot: gauging of thread, appearance; in-process tests for corrosion, thickness, adhesion; purchaser-specified tests may be supplied from in-process results. Sampling per ISO 3269 referenced. | Sampling: 1% from each batch (min 2 items per test) for thickness and adhesion; if failures occur, a further 1% is tested and batch may be rejected (Annex C sampling plans). |
| Information to be supplied by purchaser (order content) | ISO: reference to document, coating designation, material properties influenced by coating, torque/clamp requirements, tests to be carried out, sampling, color/cosmetic requirements etc. (Clause 10). | EN: purchaser shall provide standard number, designation, component metallurgy/heat treatment, significant surface & thickness requirements, tensile strength & stress relief requirement, type of coating process and adhesion requirements, supplementary coatings, accelerated corrosion test requirement, sampling/inspection requirements. |
| Examples of designation (from each standard) | ISO examples: Hexagon head bolt ISO 4014 – M12×80 – 10.9 – flZn/nc/720h ; … – flZnL/nc/480h ; … – flZn/yc/TL/720h/C. See Table 3 & Clause 9. | EN examples: Non-electrolytically applied zinc flake coating EN 13858 – Fe/iflZn4/yc ; Fe/[SR(210)3]/pflZn8/nc/T2. See Clause 5 and 5.4 examples. |
| Labelling minimum | Label must include: flZn, yc (if Cr(VI)) or nc (if Cr(VI) free), and minimum NSS hours (e.g., /480h). | EN designation itself contains full sequence including thickness (µm) and chromate indicator; labelling given by designation rules in Clause 5. |
| Notes / Warnings | ISO warns about curing effects, hydrogen embrittlement risks, and that coated fasteners must meet mechanical/assembly compatibility. ISO references multiple tests and gives fastener-specific requirements. | EN warns that NSS results are only indicative of service life, and that coating processes and parameters should be selected with part geometry/usage in mind. Also warns re: IHE where aluminium flakes form continuous bond. |
