Description
High-Permeability Magnetic Shielding Foil — For Shielding ELF Magnetic Fields
Magnetic fields can be very challenging to shield, and special materials such as MuMetal and Giron are usually required.
This product is a special High-Permeability Magnetic Shielding Foil (MuMetal) with 80% Nickel content, that has been fully heat-treated for maximum shielding effectiveness. In my opinion, this is the best material available for most magnetic shielding applications. (Be aware of similar products that are not fully treated, but sold for similar prices.)
This material is 0.004 inch thick, by 12 inches wide (roll format). It can be cut with an ordinary scissors or tin snips, and then bent into the desired shape around electrical panels and other objects that need to be shielded. It can be stapled, nailed, screwed, or taped into place. It is much easier to cut and bend into position than Giron.
Unlike some MuMetals, this particular product has been specially heat-treated for maximum “magnetic permeability” – the ability to shield magnetic fields. In fact, more than half of the wholesale cost for this product is for the special heat treatment process it receives. Lower quality products are often sold (unknowingly) at the price of the fully heat-treated materials, or the fully treated materials are priced astronomically high. It is very difficult for the average buyer to know the difference, and select the right materials.
Although the lower-quality shielding foils (those that not fully heat-treated, may only be “stress annealed”) are much cheaper to produce, they only give about one third the shielding effectiveness compared to a fully treated MuMetal. And you cannot tell just by looking at the material. You have to actually test it, which is something I do regularly with the various shielding materials.
Professionally, I have become so frustrated with the unreliable information, quality and pricing from the various suppliers, that I now order the shielding material direct from the mill myself, in large quantities, and then have it properly heat treated myself.
MuMetal is highly resistant to corrosion and UV, and thus it can be exposed to weather and sunlight (unlike Giron). But of course it is always good to protect any shielding materials from the elements if possible. This high-perm foil can be cut and bent, but should not be drilled or heated excessively. Very high temperatures can undo the special heat treatment which gives the foil its desirable magnetic shielding characteristics.
For best shielding performance, several layers of MuMetal foil may be required. In my tests, I have found that the overall cost and performance of this 0.004 inch thick “high-perm” magnetic foil is similar to that of Giron – with 3 layers of 0.004″ MuMetal being roughly equivalent to 2 layers of Giron.
I always recommend testing with a gaussmeter (e.g., the Alpha UHS2 Gaussmeter) to be sure that you are reducing the magnetic fields properly. If possible, a telephone consultation is recommended to help develop an effective shield design. Improper placement can increase the levels in certain situations. This product works well for shielding the ELF magnetic fields related to 60 Hz and 50 Hz electrical power.
Specification: ASTM A753 alloy type 4
Treatment: Fully heat treated for maximum magnetic permeability
Thickness: 4 mil (0.004 inch)
Width: 12 inches (roll format)
