FFU Housings: Galvanized vs Aluminized Zinc

Which FFU housing material should you specify?

For most cleanroom ceiling FFUs, specify a corrosion-resistant steel housing—commonly aluminized zinc (aluminum-zinc coated steel) or galvanized steel—at a gauge matched to stiffness and handling needs (often about 0.8 mm on large 1175-class modules and about 1.0 mm on compact 615×615 builds). Then confirm coatings, cleanability, and sealing details for your process—not a marketing metal name alone.

The housing is not cosmetic sheet metal. It sets filter seal integrity, fan mounting rigidity, acoustic behavior, and how the unit survives shipping, installation, and years above a classified space. Particle performance still answers to ISO 14644-1; the box is part of keeping that performance sealed and stable.

ISO 14644-1 defines cleanroom air cleanliness classes by maximum allowable airborne particle concentrations—terminal FFU housings must preserve filter sealing and structural stability so supply air actually meets those limits.
— ISO 14644-1:2015

Cabinet height and construction sit inside the same duty-point conversation as the fan curve.

Galvanized vs aluminized zinc — what buyers mean

Galvanized usually means zinc-coated steel. Aluminized zinc (aluminum-zinc alloy coated steel, often called “galvalume-type”) adds aluminum into the metallic coating system for enhanced corrosion resistance.

Exact coating standards and coating weights vary by mill and supplier. For inquiries, do not stop at the adjective—ask for:

1. Base steel + coating designation
2. Nominal thickness (mm)
3. Surface finish / passivation expectations
4. Whether powder coat or other topcoats are included
5. Cut-edge / weld touch-up practice

Senter’s published complete FFUs commonly describe aluminized zinc / galvanized construction in the 0.8–1.0 mm band depending on module—aligned with mainstream cleanroom FFU practice rather than exotic alloys for every bay.

Why 0.8 mm vs 1.0 mm gauge matters

Thicker gauge generally improves stiffness, dent resistance, and panel “drum” behavior. Thinner gauge reduces weight and can be enough when the module design and bracing are sound. Choose by handling risk and acoustic/structural needs, not by assuming thicker always equals “higher class.”

Related performance links

• Acoustics: Flimsy panels radiate more structure-borne sound when fans run hard against high filter pressure drop.
• Sealing: Warped frames threaten HEPA/ULPA integrity—filter grades are classified under EN 1822, but the frame must hold geometry.
• Install: Large 1175×1175 units are heavy; gauge and bracing affect lift safety and grid fit.

EN 1822 classifies HEPA/ULPA packs by MPPS performance; housing flatness and gasket continuity are what keep that rated media from being bypassed in the field.
— EN 1822

Comparison table: material decisions that show up in inquiries

Compare corrosion environment, cleanability, stiffness, weight, cost, and documentation—then freeze a written housing spec.

There is no universal winner. A food-adjacent humid hall, a dry electronics ISO 7, and a solvent-using process bay are different corrosion problems wearing the same “cleanroom” label.

Housing is part of the duty point (height, inlet, noise)

Material choice fails if cabinet free height cannot fit the fan + filter stack, or if the box turns every RPM into panel noise.

EC/DC platforms help because you can run only as fast as ISO validation needs. A typical estimate is about 40–50% energy savings versus AC (depending on duty-point watts and local tariff), with higher efficiency at part load and usually quieter operation at the same airflow because the fan can run slower. None of that rescues a resonating underspecified cabinet.

Neither a fan curve nor a housing drawing is enough on its own—send the material/gauge drawing package and airflow at final filter pressure drop together.

Process environments: when to stay with coated steel vs escalate

Stay with quality aluminized-zinc/galvanized FFU housings for typical dry-to-moderate cleanrooms. Escalate to special coatings or stainless only when chemical, washdown, or regulatory drivers are documented.

Coverage density (typical starting points: ISO 5 about 60–100%, ISO 7 about 25–40%, verified with ACH) multiplies housing decisions across hundreds of identical boxes—standardize early.

OEM/ODM: cosmetics must not break corrosion or seals

Private-label color, logos, and packaging are normal—but powder coat, silkscreen, and pierce locations must follow a corrosion and gasket SOP so branding does not create rust paths or leak paths.

OEM checklist

• Approved topcoat system over AZ/GI substrate
• Masking rules around gasket lands
• Hardware finish (screws, rivets) compatible with coating
• Nameplate adhesive / rivet sealed
• Edge protection after punching/cutting
• Sample salt-spray or adhesion tests if contractually required

Factories that own motor-to-complete-FFU stacks (Senter’s model) can keep sheet-metal tolerances aligned with fan clearances—reducing rubs that start as “noise complaints” and end as metal debris risks.

How Senter modules map housing language today

Always re-confirm on the quotation revision—coatings and gauges can be OEM-customized within engineering limits.

Inquiry block for housing (paste into emails)

Module size: 1175×575 / 1175×1175 / 1175×875 / 615×615 / custom ___
Substrate: galvanized / aluminized zinc / stainless grade ___
Nominal thickness: 0.8 mm / 1.0 mm / other ___
Topcoat / color (OEM): ___
Gasket / gel sealing standard: ___
Cabinet free height constraint: ___ mm
Corrosion environment notes: humidity / chemicals / washdown ___
Documentation: material certs required yes/no

Conclusion

Specify FFU housings by coating system + gauge + sealing + height, using galvanized or aluminized-zinc steel for most cleanroom ceilings (commonly 0.8 mm on 1175-class modules and 1.0 mm on 615×615), and escalate to specialty materials only with a documented environmental driver.

Keep housing inside the same duty-point inquiry as fan airflow, final filter pressure drop, noise, and control interface. Review Senter’s published modules on senter-motor.com and send substrate/gauge plus process notes for an engineered enclosure recommendation.

References

1. ISO 14644-1:2015 — Classification of air cleanliness by particle concentration
2. EN 1822 — High efficiency air filters (EPA, HEPA and ULPA)