What Does Diffusion-Limited Current Density (DLCD) Mean?
Diffusion-limited current density (DLCD) is the density of any material obtained by maintaining diffusion limits and assuring the maximum transfer rate of any material in the process of conversion between one or more particular species. In electrochemical reactions, the DLCD of any reacting material plays a significant role in kinetic control.
There are many rate-limiting factors that do not allow achievement of the maximum rate, such as availability of oxygen in solution and hydrogen-oriented reactions with iron, copper and other metals.
Corrosionpedia Explains Diffusion-Limited Current Density (DLCD)
In electrochemical reactions, the reactant that is dissolved in the solution is deposited by electron transfer at the electrode. A concentration gradient is generated. When a reasonably high exchange current density is provided, the reaction rate and current are limited by the rate at which the reactant starts to deposit at the electrode by diffusion.
DLCD is measured by the following factors, including:
- Faraday constant
- Diffusion coefficient
- Current density
- Ratio of current density to diffusion limited current density
The role of DLCD of oxygen in reduction reactions dominantly controls kinetics in corrosion. At the metal surface, oxygen must be present. In some conditions, when oxygen is quickly consumed, the rate of oxygen diffusion functions as a limiting factor. Because of this, the reactions at the cathode slow down, causing reactions at the anode to stop to conserve electrons.
DLCD is sometimes used as a parameter to study the turbulent flow in electrochemical reactions. Alteration in texture of electrolytic deposits reflects the variable ratio of current density used in the electrolytic process to the diffusion-limited current density. In any electrochemical reaction, the electrolyte influences the DLCD; ultimately, the deposit texture also varies. Research has been conducted in which DLCD is assumed as a motility character function of different electrolytes.