Electrostatic charging of powders and powder mixtures were measured
on-line during surface adhesion by sliding the powders in a pipe. The
cumulative charge was monitored as a function of transferred powder
mass. The effect of adhesion on the charging was assessed by observing
the slope of the measured curve at the very beginning of the
measurement. Due to adhesion, the charging decreased exponentially. For
mixtures, the powder with higher concentration initially dominated the
charging. The sign of the charge changed as the additive powder started
to adhere, indicating that contacts between the two dissimilar powders
started to govern the charging.