What Alloy 8011 Is and Where It Fits
Alloy 8011 is an Al-Fe-Si wrought grade from the 8xxx series that was developed specifically for thin-gauge packaging foil. Its iron and silicon additions raise strength above the 1xxx purity grades while keeping elongation high enough for deep drawing and embossing, and they also refine the as-cast structure so that pinhole levels stay low at gauges below 20 microns. Foil is defined by gauge rather than by chemistry: by convention aluminium foil is rolled material at or below 0.2 mm thick, and the same convention is used in EN 546-1 and in the Chinese foil standard GB/T 3198.
Chemical Composition and Tempers
Typical registered limits for the 8011 grade are shown below. The silicon-to-iron balance is the practical control on both strength and recrystallisation behaviour, so it is specified as a range rather than as a single figure.
| Element | Limit (wt%) |
|---|---|
| Si | 0.50 - 0.90 |
| Fe | 0.60 - 1.0 |
| Cu | 0.10 max |
| Mn | 0.20 max |
| Mg | 0.05 max |
| Zn | 0.10 max |
| Ti | 0.08 max |
| Al | Balance |
Tempers follow EN 515: O is fully annealed and oil-free, H22 and H24 are strain hardened and partially annealed for trays and lids, and H18 is full hard for structural laminates and lidding that must resist distortion. Thickness tolerances are ordered to EN 546-3 for metric markets.
Gauges Supplied in Jumbo Roll Form
| Application | Typical gauge | Usual temper |
|---|---|---|
| Semi-rigid food containers | 9 - 30 microns | O, H22, H24 |
| Pharmaceutical blister lidding | 20 - 30 microns | O, H18 |
| Laminated flexible packaging | 30 - 65 microns | O, H22 |
| Heat sealing and coating base | 20 - 50 microns | O |
| Insulation and cable wrap | 50 - 200 microns | O, H24 |
Production Route and Process Control
Rolling starts from continuously cast or direct-chill cast stock, which is hot rolled and then cold rolled in several passes. Intermediate annealing in the range of roughly 300-350 degrees C removes the work hardening introduced by each pass and restores ductility before the final reduction, and the last passes are run double so that two foil webs are rolled together and then separated. Double-zero material at 0.01 mm and below demands tight roll-gap control, filtered rolling oil and clean work rolls, because streaks, chatter marks and pinholes cannot be corrected downstream. Slitting into customer widths and winding under controlled tension complete the jumbo roll.
Barrier Performance and Quality Control
Aluminium foil is a total barrier to light, and at thicknesses above roughly 25 microns it is effectively impermeable to water vapour and oxygen; performance below that gauge depends on pinhole density rather than on published transmission rates. Buyers therefore specify pinhole count per square metre, thickness tolerance across the web and residual oil level, and verify meal and water-vapour transmission on the finished laminate using ASTM F1249 and ASTM D3985 where the packaging design depends on them.
Food-Contact and Compliance Considerations
Foil intended for direct food contact is produced to comply with framework Regulation (EC) No 1935/2004 in Europe and with FDA 21 CFR 175.300 for coated surfaces in the United States, while GB 4806.9 governs metal food-contact articles in the Chinese market. Rockwell hardness and tensile checks are run on the finished coil against the requirements of the appropriate grade specification so that forming performance is predictable at the customer press.
Frequently Asked Questions
Q: What thickness range is normally supplied as 8011 foil?
A: Jumbo rolls are produced from 0.006 mm to 0.2 mm; container stock is usually 9 to 30 microns and laminating or coating stock runs 50 to 65 microns.
Q: Which temper should be chosen for food trays?
A: H22 or H24. Both are strain hardened and partially annealed, which gives enough stiffness to hold a formed tray shape while retaining the elongation needed for the draw.
Q: Why is intermediate annealing important?
A: Each cold-rolling pass hardens the strip. Annealing at about 300-350 degrees C restores ductility so that the final passes can reach very thin gauge without edge cracking or excessive pinholes.
Q: Is 8011 foil suitable for pharmaceutical blister packs?
A: Yes, typically at 20 to 30 microns in the O or H18 temper, usually laminated or lacquered so that the lidding can be sealed to the PVC or PVDC cavity film.
Q: How is pinhole level specified?
A: As a maximum number of light-transmitting defects per square metre at the ordered gauge, checked by light-box inspection and agreed between supplier and buyer for the specific packaging requirement.
Q: Can 8011 foil be used for electrical applications?
A: It can, but higher-purity grades such as 1235 or 1060 are usually preferred where conductivity is critical, because the deliberate iron and silicon content of 8011 lowers electrical performance.