Depth of Electromagnetic Penetration
into Metals
(Skin-Effect Depth)


Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor.

From: Wikipedia. See more at https://en.wikipedia.org/wiki/Skin_effect    


Skin Effect Depths in Aluminum, Copper and Steel

EM Field
Frequency
Aluminum
(mm/µm)
Aluminum (in) Copper (mm/µm) Copper (in) Steel
(mm/µm)
Steel
(in)
10 Hz 26.7 mm
1.05
20.9 mm
0.82
 2 mm
0.08
60 Hz
11 mm
0.43
8.5 mm
0.33
0.8 mm
0.03
100 Hz
8.5 mm
0.33
6.6 mm
0.26 0.6 mm
0.02
1 KHz
2.8 mm
0.11
2 mm
0.08 0.2 mm
0.008
10 KHz
0.8 mm
0.03
0.8 mm
0.03
60 µm 0.002
100 KHz
0.3mm 0.01
0.2 mm
0.008
19 µm 0.0008
1 MHz
85 µm 0.003
66 µm 0.003
6 µm 0.0002
10 MHz
27 µm 0.001
21 µm 0.0008
2 µm 0.00008
100 MHz
8.5 µm 0.0003
7 µm 0.0003
0.6 µm 0.00002
1 GHz
2.7 µm 0.0001
2 µm 0.00008
0.2 µm 0.000008

Source: Telecommunications Distribution Methods Manual, 12th Edition; BICSI; https://www.bicsi.org/default.aspx