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ISO 27830: Designation of Metallic and Inorganic Coatings
Standardized format for designating electrodeposited, autocatalytic, and vapour-deposited metallic coatings
Introduction to ISO 27830
ISO 27830:2017 establishes a standardized format for designating metallic and other inorganic coatings, covering electrodeposited, autocatalytic (electroless), and vapour-deposited coatings. This second edition replaces ISO 27830:2008 with technical revisions and applies to International Standards for these coating types. The standard is essential for engineers and specifiers who need a clear, unambiguous system for communicating coating requirements across the supply chain — from design engineers to electroplaters and quality inspectors.
Before ISO 27830, coating designations varied significantly between standards, leading to confusion in procurement contracts and manufacturing specifications. This standard brings order by defining a modular, repeatable designation structure applicable across all metallic coating International Standards.
Designation Structure and Syntax
The coating designation comprises four main elements: the description and International Standard number modules, followed by a hyphen; the individual item module (basis material, heat treatment, coating type and thickness); and additional codes separated by solidi (/) for each stage of the coating sequence. Double separators indicate missing stages.
| Designation Example | Meaning |
|---|---|
| Electrodeposited coating ISO 1456 – Fe/Cu20a/Ni30b/Cr mc | Decorative Ni+Cr on steel: 20 μm Cu + 30 μm bright Ni + 0.3 μm micro-cracked Cr |
| Electrodeposited coating ISO 2081 – Fe/Zn12/ER(190)8/A/T2yL | 12 μm Zn on steel with chromate + sealant, embrittlement relief 8h at 190 °C |
| Autocatalytic coating ISO 4527 – Fe(G43400)/SR(210)22/NiP(10)15/Cr0.5/ER(210)22 | NiP(10%) 15 μm + Cr 0.5 μm on G43400 steel with stress relief and embrittlement relief |
| Vapour-deposited coating ISO 22778 – Fe/SR(150)2/Cd5/F | 5 μm vapour-deposited Cd on high-strength steel with black chromate |
Critical detail: coating thickness in the designation refers to minimum local thickness measured at any point on the significant surface touchable by a 20 mm diameter ball. This is NOT an average thickness — quality control plans must verify that the minimum thickness requirement is met at the thinnest point, not just the average.
Engineering Design and Quality Control Implications
The standard defines service condition numbers from 1 (mild, indoor dry) to 5 (extended very severe, outdoor with abrasion and long-term corrosion protection). Coating thickness recommendations are directly linked to service conditions — a critical relationship for design engineers. For example, a coating specified for service condition 5 will require significantly greater thickness than one for condition 1, directly impacting cost, manufacturing cycle time, and component dimensional tolerances.
The standard also addresses critical hydrogen embrittlement concerns through heat treatment designation codes: SR (stress relief before coating), HR (hydrogen embrittlement relief after coating), and HT (other heat treatments). These are specified with temperature and duration in parentheses, e.g., SR(210)2 for stress relief at 210 °C for 2 hours. For high-strength steels (tensile ≥ 1,000 MPa), hydrogen embrittlement management is mandatory.
For quality engineers, the standardized designation system enables unambiguous communication of coating requirements in purchase orders, engineering drawings, and inspection reports. The modular structure — with each coating stage separated by a solidus — allows automated parsing by procurement and quality management systems.
Frequently Asked Questions
Q: What is the difference between “electrodeposited” and “autocatalytic” coatings in the designation?
A: Electrodeposited coatings use an external electric current to drive metal deposition, while autocatalytic (electroless) coatings use a chemical reducing agent in the plating solution. The designation explicitly identifies which process is used, as they have different properties — autocatalytic NiP coatings, for instance, provide more uniform thickness on complex geometries.
A: Electrodeposited coatings use an external electric current to drive metal deposition, while autocatalytic (electroless) coatings use a chemical reducing agent in the plating solution. The designation explicitly identifies which process is used, as they have different properties — autocatalytic NiP coatings, for instance, provide more uniform thickness on complex geometries.
Q: How do I designate a coating when a particular process stage is not required?
A: Use double separators (//) to indicate missing stages in the coating sequence. For example, if no undercoat is required but a top coat is specified, the designation would show // before the top coat symbol.
A: Use double separators (//) to indicate missing stages in the coating sequence. For example, if no undercoat is required but a top coat is specified, the designation would show // before the top coat symbol.
Q: Are there standardized symbols for all common coating materials?
A: Yes. Annex A provides comprehensive tables of symbols for basis materials (Fe, Zn, Cu, Al, Mg, PL for plastics), coatings (Ag, Au, Cu, Cr, Ni, Sn, Zn, etc.), undercoats, coating types (a=ductile Cu, b=bright Ni, mc=micro-cracked Cr, etc.), chromate conversion codes, and supplementary treatments.
A: Yes. Annex A provides comprehensive tables of symbols for basis materials (Fe, Zn, Cu, Al, Mg, PL for plastics), coatings (Ag, Au, Cu, Cr, Ni, Sn, Zn, etc.), undercoats, coating types (a=ductile Cu, b=bright Ni, mc=micro-cracked Cr, etc.), chromate conversion codes, and supplementary treatments.
Q: Does ISO 27830 apply to thermally sprayed or porcelain enamel coatings?
A: No. The standard explicitly excludes thermally sprayed and porcelain enamel coatings. It applies to electrodeposited, autocatalytic, and vapour-deposited coatings only.
A: No. The standard explicitly excludes thermally sprayed and porcelain enamel coatings. It applies to electrodeposited, autocatalytic, and vapour-deposited coatings only.
