Stray currents corrosion of underground steel pipelines

Groza Stefana MadalinaISBE, 2nd year

ELECTROMAGNETIC POLLUTION

Earth’s molten iron-nickel core

Charged gases of the ionosphere

Resonances

Biological time clocks

MAN ANIMAL PLANT

DISCOMFORTDISORIENTATION

DEATH

ALL TYPES OF BACKGROUND RADIATION HAVE INCREASED SO DRASTICALLY AND SO QUICKLY IN THE LAST FIFTY YEARS THAT WE

CAN NO LONGER HOPE TO COPE WITH THEM.

STRAY CURRENT CORROSION

ELECTROMAGNETIC FIELDS

NATURAL PROCESSES

THERMAL SIDE EFFECT

ELECTRIC AND MAGNETIC COMPONENTS

TECHNOLOGICAL AND INDUSTRIAL DEVELOPMENT

PRODUCTION AND CONSUMPTION OF ELECTRICITY

ELECTROMAGNETIC POLLUTION

THE CORROSION OF THE UNDERGROUND STEEL PIPELINES

The first mobile laboratory specialized in investigating and determining the dispersion in DC currents (Los Angeles, 1910)

Stray currents may originate from

• cathodic protection system

• electrical welding machines

• grounded dc electric sources

• street railway systems, etc

Stray current corrosion

DC traction system

In this case rails act as primary current return path and the surrounding ground acts as a conductor that can carry stray currents. There is a fundamental tendency for the return current in the rails to flow from the train to the substation. Because the tack is not perfectly insulated from the ground, there is a tendency for the current to flow in the ground in the same direction. Here the stray current will be picked up by the pipeline near the train and discharge near the substation.

The corrosion resulting from stray currents (external sources) is similar to that from galvanic cells (which generate their own current) due to the fact that the corroding metal is again considered to be the anode from which current leaves to flow to the cathode.

Soil and water characteristics affect the corrosion rate in the same manner as with galvanic-type corrosion.

Despite the apparent similarity, stray current strengths may be much higher than those produced by galvanic cells and thus corrosion may be much more rapid. Moreover, seeking the path of least resistance, the stray current from a foreign installation may travel long distances along a pipeline causing severe corrosion where it leaves the line.

Accentuated degradation of the fastened elements in the Budapest’s subway

The corrosion of the gas pipes due to the stray DC currents which originate in Bucharest’s tram and subway

Damages of the pipeline in Cluj-Napoca

Stray current corrosion prevention

Eliminate or reduce stray current

Acting on the source instead on the consequences

Increasing the global circuit resistance

CATHODIC

PROTECTION

•sacrificial anodes•impressed current/voltage anodes

CURRENT

DRAINAGERS

•varying the boosting DC voltage•changing the resistance of the direct connection

• bringing the galvanic potential of the metal to a level where the anodic reactions are impossible for the given circumstances• an external current that reduces or inverses the anodic current.

• possible when the sources of the stray currents are accessible• the connection is made unidirectional, such that current can only flow from the buried structure to the negative pole of the DC source, thus rounding the electrolyte (the soil)

Bibliography

www.radioamator.rowww.corrosion-doctors.org

www.enotalone.comwww.google.com