Causes of Static Electricity
Brass, stainless steel
Generation of static electricity on an object by
rubbing is known as the triboelectric effect. The
following is a list of substances in the triboelectic
series. The list is arranged in such an order that when
any two substances in the list contact one another and
then separate, the substance higher on the list assumes
a positive charge.
The size of an electrostatic charge on two
different materials is proportional to the separation of
the two materials.
Electrostatic voltage levels
generated by nonconductors can be extremely high.
However, air will slowly dissipate the charge to a
nearby conductor or ground. The more moisture in
the air, the faster a charge will dissipate. Table 10-1
shows typical measured charges generated by
personnel in a manufacturing facility. Note the
decrease in generated voltage with the increase in
Nickel, copper, silver
humidity levels of the surrounding air.
Table 10-1.-Typical Measured Electrostatic Voltages
VOLTAGE LEVELS @ RELATIVE HUMIDITY
MEANS OF STATIC GENERATION
WALKING ACROSS CARPET
WALKING OVER VINYL FLOOR
WORKER AT BENCH
VINYL ENVELOPES FOR WORK
COMMON POLY BAG PICKED UP FROM
WORK CHAIR PADDED WITH URETHANE