(11) Friction coefficient measurement method

Lubricants strongly adhering to metal surfaces lower friction coefficient. Similarly, existence of organic substance, or contaminants also alter the friction coefficient.
This principle can be used to measure the friction coefficients by using a slider on contaminated metal surfaces as shown on [Fig.1] by converting the force acting on the slider into friction coefficient by a strain gauge. The amount of lubricity by the contamination is determined by varying the loads on the slider and by obtaining friction force variations over time.

(12) Contact potential difference test

The bonding strength of organic substances on metal surfaces is related to the organic substance's affinity to the metals. This is a contamination measurement method utilizing this principle by measuring the contact electrical potential differences.
The contact potential electrical difference is the potential difference between clean metal surface and organic substance contaminated metal surface. The differential value would be zero if there is no contamination, and the value would vary depending on the amounts of contamination. The [Table 1] shows potential differences of stearic acid on metal surfaces. Similar single molecular contamination on platinum and nickel oxide would vary in removals, due to the differences in Adsorption power.

[Table 1] Removal of stearic acid single molecular contamination on metal surfaces

(13) Other

There are other methods such as: Weighing method and Ellipsometry method.