The Kinetics of Electrode Reactions: Part II—Mass Transfer and Mixed Control

SUMMARYThe modes of mass transport to and from electrode surfaces are considered and it is seen that the rate of reactant supply is often a rate determining step in electrochemical reactions which occur in metal finishing. Complete mass transport control is characterised by the limiting current for a reaction and expressions are developed which relate this parameter to reactant concentration and electrode/electrolyte velocity. In many cases, reaction rates are governed partially by mass transfer and partially by electron transfer. This, “mixed control” case is also considered by means of current versus potential curves and the types of overpotential involved.