45 x 90 mm Aluminium Profile for Pharma Cleanroom Framing

01Why does a cleanroom frame built from bare profile fail a GMP walkthrough?

Not because the aluminium is wrong. Because the geometry of a butt joint is a dust trap. Where two 45 x 90 extrusions meet at 90 degrees, the inside corner is a square recess roughly 45 mm deep with a radius of about 1 mm at the root. A wipe moving across that corner bridges it, lifts, and leaves a film of residue in the root. Over a qualification cycle the residue accumulates, and the swab result eventually shows it.

The fix is not a better extrusion. It is a coved cover: a radiused fillet piece that sits over the internal corner and presents a surface a wipe can follow continuously. The usual radius is 25 mm or more, and the cover has to be removable for cleaning behind it, which means it is a separate part, not a welded or bonded detail.

• Internal corners need a coved cover of 25 mm radius or greater; a 5 mm fillet is cosmetic and still traps.
• External corners are less critical but should be radiused, because a sharp arris sheds particles when a trolley hits it.
• The profile to cover interface must be sealed, not just butted, or the gap becomes a horizontal ledge.
• Avoid any horizontal surface wider than about 10 mm anywhere above floor level; that is the rule auditors apply in practice, whether or not it is written down.

02What surface finish is actually cleanable?

Roughness matters more than gloss, and the two are not the same thing. A bright anodised surface reads as clean to the eye and can be the harder one to wipe, because the bright finish is produced by chemical polishing, which rounds and deepens the micro-profile rather than flattening it. A matte or satin etch gives a lower Ra and a more repeatable wipe.

For an extruded frame, the surface the wipe touches is the extrusion surface, not a machined one. That means the Ra is set by the die bearing and the etch, typically in the 0.6 to 1.2 micrometre band for a satin etch, and it cannot be improved after the fact without machining the faces, which is expensive on a 6 m length.

One more point that surprises people: the anodic film itself is porous before sealing. A sealed film is chemically inert and wipes clean; an unsealed or poorly sealed film absorbs residue into the pore structure and then releases it slowly, which shows up as recurring failures at the same swab point. Ask for the seal quality test, not just the thickness.

03Which cleaning agents attack the anodic film, and how fast?

The anodic film is aluminium oxide, which is amphoteric: it dissolves in both acid and alkali. That single fact drives the whole compatibility table, and it is why a cleaner that works perfectly on stainless steel can destroy an anodised frame in a year of daily use.

04How is differential pressure held at the frame, not the panel?

A cleanroom holds 10 to 15 Pa between a graded room and its neighbour, and the frame’s job is to not be the leak. The panel is usually the tight element; the frame is where the leaks are, at three places: the panel to profile joint, the profile to profile joint, and the profile to floor or ceiling joint.

The panel joint is a gasket compressed between the panel edge and the profile face. Gasket compression should sit between 25 and 30 percent of free height. Below 20 percent it leaks under pressure; above 40 percent it takes a permanent set and leaks later, which is worse because it passes the initial test and fails in year two.

1. Panel to profile. Continuous gasket, 25 to 30 percent compression, no butt joints in the gasket at a corner. Corners are mitred and bonded.
2. Profile to profile. Sealant in the joint, and the sealant must be neutral cure silicone. Acetoxy cure releases acetic acid as it sets, which attacks the anodic film and leaves a chalky line that shows up on a wipe test.
3. Profile to floor. A continuous bead, not a spot fix, and a floor channel rather than a direct fix, so the bead is in compression rather than shear.

Then test it. A pressure decay test at 50 Pa on a closed room, with the frame penetrations temporarily sealed, tells you whether the frame or the services are the leak. Doing that before the ceiling goes in saves a week of chasing.

05Why are zinc plated connectors a problem in a graded room?

Two reasons, and the second one is the one that gets missed. First, a zinc or zinc nickel plated connector inside a profile slot is a coated part in a washdown environment; the coating wears at the contact points and the exposed zinc corrodes, producing a white salt that migrates out of the slot. Second, and more important for particle counting, the plating itself can shed.

The practical alternatives are stainless connectors, or aluminium connectors with a clear anodised finish, or a zinc flake coating if the load requires steel. Stainless against aluminium introduces a galvanic couple, so the joint needs an isolating washer or a sealant barrier; that is a real trade-off, not a free upgrade.

06What does the audit actually look at?

Not the alloy certificate, in most cases. The auditor walks the room and looks at surfaces, joints and the cleaning record. The frame comes up in three specific ways, and knowing them at design stage is worth more than any test report.

07What five numbers should be on the enquiry?

A cleanroom frame is quoted from the room, not from the profile. Give us the room and the grade, and the section follows.

Room size and grid

length, width, height, and the panel module, because the grid pitch follows the panel

Grade and pressure

ISO 14644 class or Grade C/D, and the pressure differential in Pa

Cleaner list

the actual agents in the SOP, because hypochlorite changes the finish specification

Corner detail

coved covers supplied or not, and the radius required by your QA

Delivery and installation

flat packed with covers and gaskets, or frame only

Section

45 x 90 mm six slot at 4.10 kg/m as standard, 4.85 kg/m heavy wall for spans over 2.4 m

Related sections and categories

The same 45 mm pitch family is listed under 45 Series Aluminium Profiles. For longer ceiling spans the 45 x 90 mm heavy wall section at 4.85 kg/m is the direct upgrade, and the finish options are set out in anodised aluminium profiles.