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BS EN ISO 14713 — Zinc Coatings: Guidelines for Corrosion Protection of Iron and Steel in Structures
Zinc Coatings — Guidelines and Recommendations for the Protection Against Corrosion of Iron and Steel in Structures Series
🛡️ The BS EN ISO 14713 series is a set of British Standards implementing the European standard EN ISO 14713 in the field of zinc coatings, providing guidelines and recommendations for the corrosion protection of iron and steel structures. The series was prepared by ISO/TC 107 (Metallic and other inorganic coatings) and CEN/TC 262 (Metallic and other inorganic coatings), with BSI holding the secretariat of both committees and UK participation entrusted to Technical Committee STI/34 (Hot dip galvanized coatings). The series supersedes the 1999 edition of BS EN ISO 14713 and is divided into general principles, hot dip galvanizing and sherardizing. The ICS classifications are 25.220.40 (metallic coatings) and 91.080.10 (metal structures).
💡 Zinc provides sacrificial-anode cathodic protection to steel, making it one of the most economical and effective long-term corrosion-protection methods for steel structures. The ISO 14713 series systematises design selection, coating processes and acceptance requirements, helping engineers plan the corrosion-protection route at the structural design stage.
1. Series Composition 📌
The series comprises three documents (2009/2010 edition), corresponding to design principles, hot dip galvanizing and sherardizing:
| Standard | Year | Title / Subject | Main Content |
|---|---|---|---|
| BS EN ISO 14713-1 | 2009 | General principles of design and corrosion resistance | Corrosion-protection design principles, environmental corrosivity classification and coating selection |
| BS EN ISO 14713-2 | 2009 | Hot dip galvanizing | Hot dip galvanizing process, coating requirements and quality control |
| BS EN ISO 14713-3 | 2009 (2010 corrigendum) | Sherardizing | Sherardizing process, coating requirements and applications |
⚠️ The series supersedes BS EN ISO 14713:1999 and splits its content into three parts. Design documents and procurement specifications should reference the relevant part of the new edition.
2. General Principles of Design and Corrosion Resistance (Part 1) 📐
Part 1 specifies the general principles of corrosion-protection design for steel structures, including corrosion environment classification, steel surface condition, the effect of structural geometry on coatings, selection of coating process, and coordination of coatings with subsequent painting (the “duplex system” of galvanizing + paint). Design should consider drainage, ventilation, avoidance of crevices and maintenance accessibility to ensure coating performance and structural durability.
3. Hot Dip Galvanizing (Part 2) 🔥
Part 2 specifies the guidelines and recommendations for hot dip galvanizing, covering steel surface pre-treatment (degreasing, pickling, fluxing), immersion parameters, coating thickness and uniformity requirements, test methods and defect handling. Hot dip galvanizing forms a metallurgically bonded zinc-iron alloy coating by immersion in a molten zinc bath, suited to large structural steel items with excellent corrosion life and mechanical properties.
4. Sherardizing (Part 3) ⚙️
Part 3 specifies the guidelines and recommendations for sherardizing. Sherardizing places workpieces in a rotating container with zinc powder and heats them so that zinc vapour diffuses into the steel surface to form a zinc-iron alloy coating. This process suits small parts, threaded components and complex shapes, giving uniform coatings without hydrogen-embrittlement risk, and is a common corrosion-protection method for fasteners and hardware. The March 2010 corrigendum issued by CEN has been incorporated into this British Standard.
🚨 The premise of coating corrosion protection is a complete, dense coating of adequate thickness for the service environment. Runs, blisters, uncoated areas on galvanized items and non-uniform sherardized coatings should be rejected; coating repair per specification is required where cut or drilled after coating.
5. Engineering Practice and Corrosion-Protection Design 🛠️
- 🔍 Environmental classification: determine the corrosivity category per environment (e.g., ISO 9223) and select the corresponding coating thickness and process.
- 📋 Process selection: use hot dip galvanizing for large components and sherardizing for small parts and threaded items; use the duplex system where longer life is required.
- 🏗️ Structural design: plan drainage, ventilation and lifting holes at the design stage, avoiding crevices and water accumulation that cause local corrosion.
- 📊 Quality control: inspect coating thickness and adhesion per standards such as ISO 1461 (hot dip galvanizing), retaining galvanizing records.
6. Frequently Asked Questions ❓
❓ Q: What is the difference between ISO 14713 and ISO 1461?
A: ISO 14713 is guidelines and recommendations for corrosion-protection design (process selection, design, quality-control recommendations), while ISO 1461 specifies requirements and test methods for hot dip galvanized coatings on products. The former guides “how to design and select”, the latter specifies “how to accept”.
A: ISO 14713 is guidelines and recommendations for corrosion-protection design (process selection, design, quality-control recommendations), while ISO 1461 specifies requirements and test methods for hot dip galvanized coatings on products. The former guides “how to design and select”, the latter specifies “how to accept”.
❓ Q: How are hot dip galvanizing and sherardizing chosen?
A: Hot dip galvanizing suits large, open structural items with thick coatings and long life; sherardizing suits small, threaded and precision parts with uniform coatings and minimal dimensional change. Choose by workpiece size, shape and service environment.
A: Hot dip galvanizing suits large, open structural items with thick coatings and long life; sherardizing suits small, threaded and precision parts with uniform coatings and minimal dimensional change. Choose by workpiece size, shape and service environment.
❓ Q: Why does zinc protect steel?
A: Zinc has a more negative potential than steel, so it corrodes preferentially (sacrificial anode) in corrosive environments, providing cathodic protection to exposed steel substrate; zinc corrosion products are also dense, forming a physical barrier.
A: Zinc has a more negative potential than steel, so it corrodes preferentially (sacrificial anode) in corrosive environments, providing cathodic protection to exposed steel substrate; zinc corrosion products are also dense, forming a physical barrier.
🔍 Q: How are galvanized items handled after cutting?
A: Cutting and drilling damage the coating; damaged areas must be repaired per specification (e.g., zinc-rich paint or thermal spray zinc) to maintain corrosion-protection integrity.
A: Cutting and drilling damage the coating; damaged areas must be repaired per specification (e.g., zinc-rich paint or thermal spray zinc) to maintain corrosion-protection integrity.