A node electrode system can be defined as a system with a network of electrodes. A new node
electrode concept is proposed for real-time monitoring of the degradation of concrete rebars and buried
pipes and to measure the corrosion rate of the metals at selected locations over a large area. In this
concept, a selected number of long metal bars are used as the working electrodes for the monitoring
system. The long bars are coated such that only selected sections are exposed to the concrete or soil.
Each exposed section has a well-defined surface area for corrosion rate measurement. The collection
of the exposed sections forms a network of electrodes, and each exposed section is a node electrode.
The network of node electrodes can be used to conveniently monitor the health conditions of the metals
it represents over a large area with only one instrument channel. If a potential problem is identified from
the node electrode monitoring system, a counter electrode can be placed near the individual nodes that
are suspected to have the high corrosion rates to measure the corrosion rate of these nodes. Therefore
this concept allows surveillance of the corrosion of concrete rebar or buried pipes over a large area and
measurement of the rate of corrosion on the metal that is aged in the same concrete or same soil for
the same time duration as the actual concrete rebar or buried pipes. For the case of concrete rebars,
the long bars used as the working electrode can themselves be actual rebars in the concrete structure.
Experiments were conducted to determine the optimum distance between neighboring nodes for
corrosion rate measurement in concrete blocks. The relationship between the corrosivity of the
concrete or size of the node electrodes and the distance required to minimize the effect of neighboring
electrodes on the accuracy of the corrosion rate measurements are discussed.
Keywords: corrosion in concrete, corrosion in soil, rebar corrosion, external corrosion, corrosion
sensors, linear polarization resistance sensor, multielectrode sensor, node electrode