Aluminium is softer than steel and marks more easily, so the ring has two jobs on an aluminium coil: spread the face load and keep anything hard away from the surface. The material choice barely changes; the cleanliness and the surface of the board change a great deal.
Why aluminium is less forgiving
A steel coil tolerates a scuff that an aluminium coil shows as a mark. The same contact pressure that leaves steel acceptable leaves aluminium visible, so the ring has to be clean and smooth rather than merely present.
Grit is the real enemy. A ring stored open in a plant with swarf on the floor will transfer that swarf to the coil face under stack load, and the mark it leaves cannot be polished out.
Specification at a glance
The ring is cut like any other; what changes is the surface requirement and how it is packed before use.
| Coil | Ring | Note |
|---|
| Mill finish | Standard board | Clean, dry |
| Coated coil | Smooth facing | Wrapped until fitting |
| Painted coil | Smooth facing | Highest cleanliness |
| Oiled coil | Dry board | No staining risk |
| Face stacked pair | Thicker board | Separates the two faces |
Mill finish, coated and painted coil
Mill finish is the most tolerant but still marks. Coated and painted coil is the least forgiving, and there the ring should be smooth faced and kept wrapped until the moment of fitting.
Where the coil is oiled, the oil and the board interact. A dry board is fine; a damp board against oiled aluminium is a staining risk.
Separation between coils
Aluminium coils stacked face to face will mark each other. The ring is the separator at the rim, and it needs to be thick enough that the two faces do not touch when the strap pulls them together.
That is a different requirement from load spreading, and it is worth stating which one the ring is buying.
Questions buyers ask before ordering
Will a paper ring mark aluminium?
A clean dry ring does not. Grit between ring and coil does.
What board for painted coil?
A smooth facing, kept wrapped until it is fitted.
Is a ring needed on both coils in a stacked pair?
At least one, and thicker where the two faces would otherwise touch.
Can the ring be used with oiled coil?
Yes, with a dry board to avoid staining.
Does the ring protect the coil body?
No, it protects the face edge and separates faces.
Tell us the ring diameter, quantity per shipment and how it is fitted at mona@hengnicepacking.com and we will advise on the board build.
