This chapter presents electrochemical methods and their use for the study of transfer phenomena in the vicinity of walls. The principle of the electrochemical method is based on mass transport in a flow in the vicinity of an electrode, where electrochemical reactions occur and the limiting diffusion current is measured. Depending on configuration, the method provides access to local and global mass transfer coefficients and to drag coefficients. The method can be used in laminar and turbulent flows. For the latter, various signal processing methods are presented so that intrinsic characteristics of the turbulence can be identified as accurately as possible based on the fluctuations of the limiting diffusion current. A significant part of the chapter is dedicated to electrochemical measurements in non-Newtonian fluids, rheological aspects and hydrodynamic drag reduction mechanisms in the case of long chain polymers and other additives.