Evaluation of the electrical properties of carbon electrodes developed with bio-material additions as a sacrificial anode in cathodic protection

Abstract

The use of zinc and magnesium sacrificial anodes for the protection of steel structures in cathodic protection techniques have been widely accepted but longevity and environmental friendliness of these materials in service still needs to be improved. Thus, the need to continually develop anodes that can potentially serve the same purpose and/or better performance. This work is a feasibility study on the production of carbon electrodes for possible application as sacrificial anodes for the cathodic protection of mild steel. The main aim of this investigation is to develop an electrode from carbon-based materials with a view to producing anodes that can potentially replace zinc and magnesium electrodes for cathodic protection of low-carbon steel. The electrodes were developed using mixture of coal, charcoal, mill scale, wood dust and coal tar (binder) that were heated and compressed in a metal die. The current passing through the electrodes was measured with the resistance, resistivity and conductivity determined, including the current densities (Iρ) which gives an indication of the electrochemical behavior of the electrodes. Morphology of the electrodes were examined by optical microscope (OM) and scanning electron microscope (SEM) to assess the influence of porosities of the electrodes produced. Based on these findings, it was generally observed that the conductivity increases from 5.23E-4 S/m to 5.87E-3 S/m for 150 µm and 600 µm particle sizes, respectively. Generally, resistivity increases with an increase in the amount of wood dust in the carbon anodes developed. The carbon electrode of 600 µm particle size with the composition of 67 wt% coal, 5 wt% charcoal, 10 wt% coal tar, 10 wt% mill scale and 8 wt% wood dust had the best current density that could offer corrosion protection for mild steel.