Abstract:
Based on proposed electrical concept of corrosion process, it is possible to simulate
buried bare pipe segment with the surrounding soil medium by an electric circuit where
the circuit electric quantities are function of the electrochemical properties of the soil as
4th degree polynomial equations. The equivalent cylindrical electrolytic capacitor
between the pipe and the remote earth and the potential across it, verifies the equation
that charge Q = C × V at natural condition with & without applying cathodic protection
system. The created positive charges consists with an equivalent negative charge
(electrons losses) a charged stray electrolytic capacitor between the pipe and the earth
through thin film soil layer around the pipe as cylindrical capacitor. The amounts of
these charges are depending on the electrochemical properties of the soil which are
surrounding the pipe segment, the length of the pipe segment and its diameter. The rate
of discharge (equivalent to capacitor self discharge) is to be considered as the corrosion
current. That's beside the facts deduced before that all electrical parameters prints &
equations are function of the electrochemical properties of soil medium around the pipe
at different cathodic protection levels. The error of these new equations of the electrical
parameters reduced to be less than ± 5%. This will help to study both the corrosion
problem and cathodic protection for a complete pipeline by an electric concept with an
electric analogue circuit which is the aim of this study. This will help, in the future, in
the choice of pipeline route, pipeline cathodic protection design and cathodic protection
maintenance process for the pipe line along its route, however long it is.