May 18, 2009

Coefficient of Friction Materials and Surfaces - Steel, Aluminum, Cast Iron

Friction Coefficient Between Two Surfaces Illustration


Coefficient of friction between Steel on Steel, Steel On Aluminum, Steel On Cast Iron, Cast Iron On Cast Iron can be found on the following table. The connected surfaces depends on the material of the connected parts, roughness, surface treatment and degreasing of the connected surfaces. And also the following table shows the coefficient of friction for different surface finishes combinations. These data will be highly useful while designing sliding mechanisms, bolted connection design where shear load is applied, etc.


Surface treatment

Material of the clamped parts

Steel on steel

Steel on cast iron

Cast iron on cast iron

Aluminum alloys

Machined degreased surfaces

0.12 ... 0.18

0.15 ... 0.25

0.18 ... 0.25

0.08 ... 0.15

Areas without surface treatment

0.15 ... 0.25

0.18 ... 0.30

0.20 ... 0.30

0.12 ... 0.20

Scorched surfaces

0.35 ... 0.55


Sand blasted surfaces

0.45 ... 0.55



Note that these frictional coefficients are for not plastic welded connections where huge bonding force are applied. Thus for plastic welded connections frictional coefficients will be much higher. (almost 0.9)  

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