Coefficient of Friction between Anodized Aluminum and Steel

First a short introduction to friction and the friction coefficient.

Friction is the force resisting when two parts are moved against each other. This can be between solid surfaces, fluid layers and/or material elements. The subject here is between two solid surfaces, also called dry sliding friction, no fluid in the sliding area.

The coefficient of friction is defined by the applied load between two parts, L, and the resultant friction force required to slide the two parts, F.

The Coefficient of Friction, µ, is given by
µ=F/L (the value is dimensionless).

The dry sliding friction coefficients vary a lot depending on the surfaces characteristic of the two parts. It is important to mentioned here that all friction coefficient values should be treated with caution because the value is very dependable of the environment and operating conditions.

The following table is taken from SIS Handbook, Aluminium, ed. 3, June 2003 and edited by me. The aluminum alloy used is not mentioned.

Against steel

Against its self

Hard anodizing





Hard anodizing with Teflon





* from Wikipedia

The value of the friction coefficient has to be dependent on the uniformity and quality of the anodic layer formed. So therefore the value would be dependent of the aluminum alloy used because of the difference in quality of the anodic layer.

For any specific application the ideal method of determining the coefficient of friction is by trials.

As mentioned above sometimes there is a fluid layer involved which will immediately change the picture. This figure is taken from The English Surface Finishing Company, Poeton.

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