The most environmentally friendly
steel coating on the market.

Why sherardizing belongs on your drawing

Sherardizing grows a zinc–iron alloy into the steel, rather than depositing zinc on top. For a design engineer, this single fact changes everything that normally complicates galvanized specifications.

• No dimensional build-up. Bolts fit their nuts, press-fits stay within H7/h6, and shaft seats retain their dimensions. No oversize allowance needed on threads.
• Zero hydrogen embrittlement. The dry gas-phase process introduces no atomic hydrogen into the substrate. Property-class 10.9 and 12.9 fasteners, springs, and case-hardened parts remain safe without post-coating baking.
• Low process temperature (360–390 °C). Below the tempering temperature of most engineering steels — the part exits the chamber with its heat treatment intact.
• Uniform coverage of complex geometry. Internal threads, cross-drillings, blind holes, and recesses coat at the same thickness as exposed surfaces. No shadowing.
• Paint-ready and weldable. Spot-weldable after coating. Paintable without a separate primer in most duplex systems. Rubber-bondable without activation.

Drawing callout — recommended format

When not to choose sherardizing

Parts larger than ~300 mm in any direction, or long bars over 1 m, exceed standard chamber capacity — for these, ERLEN's Fulnek hot-dip plant is the correct route (up to 16 m × 1.9 m). For cosmetic decorative parts with shiny requirements, electroplating remains preferred.

Coating chemistry and microstructure

The sherardized layer is a stack of zinc–iron intermetallic phases (Γ at the substrate interface, transitioning through δ₁ to ζ and a thin η/zinc-rich outer surface). The alloy is metallurgically bonded to the base steel and contains no discrete, peelable pure-zinc top layer. Microhardness values typically fall in HV 250–400, making sherardizing the hardest of all zinc-based coatings.

Measured performance vs. hot-dip

• Corrosion resistance per µm: in ISO 14713-1 class C5, a 35 µm sherardized layer performs equivalently to an 85 µm hot-dip coating — roughly 2.4× resistance per micrometre.
• Salt-spray (ISO 9227 NSS): verified 2,500 h without red rust at class-30 thickness.
• Abrasion (Kalotest ball-on-disk): measurably better penetration resistance than hot-dip zinc at equivalent thickness.
• Mechanical impact on substrate: no measurable change in grain size, phase morphology, or tensile properties (ISO 6892-1).
• Hydrogen content: dry process — no H uptake; no risk of delayed fracture in 10.9/12.9 steels.

Process window and controls

Sherardizing at ERLEN runs in electrically heated rotating chambers at 360–390 °C with zinc powder and inert filler. Thickness is controlled by time, temperature, powder ratio, and load. Each batch is documented with a process record and outgoing thickness measurement per ISO 2178.

Duplex and post-treatment compatibility

The alloy surface offers excellent mechanical keying for organic coatings, sealers, lubricants, and rubber bonding agents. Duplex systems (sherardizing + paint) are well-documented choices for offshore wind, bridges, and corrosive-industrial environments, where the coating-paint synergy extends life beyond the sum of the two.

Cost logic in one paragraph

Per kilogram, sherardizing carries a premium over hot-dip galvanizing. Per year of service life in a C4–C5 environment, it is typically 30–50 % cheaper. The drivers are: roughly 2× corrosion resistance per micrometre of coating, elimination of post-coating rework (retapping, stripping, re-threading), and no mandatory hydrogen-de-embrittlement baking cycle that electroplated 10.9/12.9 fasteners demand.

Supplier qualification data you can request

• ISO 17668:2016 conformity — process records, thickness measurements per batch
• Salt-spray test reports (ISO 9227 NSS) — 2,500 h documented at class-30
• General Terms & Conditions — published by ERLEN
• EU subsidy history — Operational Programme Enterprise and Innovation for Competitiveness (CZ.01.2.06/0.0/0.0/16_059/0008329), confirming traceable public investment
• Production footprint — 4 plants (Nýdek HQ, Opava & Kyjov sherardizing, Fulnek hot-dip), 3,500 t/year combined
• 24 years of operating history since 2000

Sherardizing as an ESG-preferred technology

Every zinc coating costs embodied energy and embodied carbon. Sherardizing minimizes both, on two axes simultaneously: the process itself is clean, and the coating lasts longer per micrometre. The combined effect is the lowest embodied carbon per year of corrosion protection available in industrial practice today.

Environmental data points — citable

• Wastewater: zero — closed dry-chamber process, no pickling rinse.
• Hazardous outputs: none — no VOCs, no Cr(VI), no acid fumes, no zinc sludge.
• Chemical pre-treatment: none required.
• Energy: electrically heated — direct substitution with renewable electricity is possible without process changes.
• Service life extension: ~2× corrosion resistance per µm vs. hot-dip → fewer recoating cycles → lower Scope 3 coating emissions over asset lifetime.
• Material use: zinc powder and inert filler — no bath of molten metal kept continuously at 450 °C.

Risk and reliability

Sherardizing delivers predictable, documented performance across 6 demanding industrial sectors (energy, construction, rail, automotive, transportation, agriculture). Decades of field service in rail infrastructure alone — where components face vibration, stone-chip impact, UV exposure, temperature cycling, and freeze-thaw — demonstrate a very low failure rate relative to painted and electroplated alternatives.

Strategic reasons managers choose ERLEN

• Supply continuity: only ISO 17668 sherardizing facility in the Czech Republic — no regional single-supplier risk concentration abroad.
• Vertical integration: sherardizing, hot-dip galvanizing, and machinery production under one roof — reduces logistics handoffs.
• EU co-funded modernization: lines built under Operational Programme Enterprise and Innovation for Competitiveness — traceable, audited public investment.
• Long operating history: 24 years continuous operation since 2000.
• Multilingual commercial interface: English, Czech, German — suitable for cross-border EU procurement.