Electrolyte agitated

Table 10.36 EITect of electrolyte agitation on corrosion rate and the current density to maintain passivity of mild steel in acid solutions at 27°C (after Walker and Ward )...

The mechanism of particle incorporation is treated extensively in the next section, but a generalized mechanism is given here to better comprehend the effects of the process parameters. Particle incorporation in a metal matrix is a two step process, involving particle mass transfer from the bulk of the suspension to the electrode surface followed by a particle-electrode interaction leading to particle incorporation. It can easily be understood that electrolyte agitation, viscosity, particle bath concentration, particle density etc affect particle mass transfer. The particle-electrode interaction depends on the particle surface properties, which are determined by the particle type and bath composition, pH etc., and the metal surface composition, which depends on the electroplating process parameters, like pH, current density and bath constituents. The particle-electrode interaction is in competition with particle removal from the electrode surface by the suspension hydrodynamics. 

Macrothrowing power predicts the ability of an electrolyte to lay down as nearly as possible a uniformly thick deposit across the surface of a workpiece. A good covering power is a prerequisite for good macrothrowing power. Other factors that affect macrothrowing power include the current distribution and current density, electrolyte composition, electrolytic conductance, and electrolyte agitation. 

In the case of precious metals, optimization of the electrolytic cell is not usually critical Indeed, a number of radically different types and size of reactor compete satisfactorily for a given application, especially when the concentration of dissolved metal is relatively high. Cell voltage (and, hence, the electrolytic power requirement) and electrolyte agitation costs arc not usually critical rather, security of the deposited metal from theft and the need to produce a relatively pure metal in a form suited to refining (or reuse) is paramount... 

Cost of electrolyte agitation Working capital Total scrap value of plant Heat capacity at constant pressure Equivalent diameter of a flow channel Depreciation year... 

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