An apparatus and method for removing a coating of undesirable material from a substrate of desired material by impacting the coating with narrowly focused streams of fluid discharged at high velocity from nozzle tips rotated rapidly by a nozzle head during linear, relative movement between the nozzle head and the coated substrate. The nozzle head may be rotated by a motor or self-actuated by tilting the tips out of the plane of the spin axis. The nozzle tips also may be canted radially to undercut and peel away the coating. The nozzle assembly may be continuously or intermittently actuated, fixedly or movably mounted, and used singularly or in plural array. Specific applications are described for descaling metal, cleaning electrolytic bath deposits from electrodes, and removing resinous materials from metal surfaces.