CORROSION
ADVANTAGES
In environments where it can be readily
used, cathodic protection is signi cantly
less expensive than coating components.
Sacri cial cathodic protection, which
requires no power source, is particularly
cost-e ective and easy to maintain.
Traditionally in marine environments,
sacri cial plates have been used to protect
the propeller and rudder of boats and
ships. Sacri cial plates are also a coste
ective way of preventing corrosion in
tanks containing electrolytes, with the
anode typically positioned in the centre of
the tank and connected to the walls with
wire. Protection can be increased by using
more anodes to increase the current.
For structures buried in soil, sacri cial
cathodic protection can be provided by
a back ll containing many small anodes
mixed with bentonite clay and gypsum.
Such back ll can be purchased premixed,
and can typically provide protection for up
to 20 years.
Impressed-current cathodic
protection is becoming a preferred
method of corrosion protection for many
CHAIN GANG
Norwegian company Imenco Corrosion
Technology (ICT) has launched the
Pacu cathodic protection technology
for marine mooring chains.
Comprising ICT’s Piranha clamp
and an integrated bracket-mounted
sacri cial anode, the solution is said to ‘dramatically’
extend the lifespan of mooring chains. Pacu can be retro tted to existing
chains. The cathodic protection of chains opens up the opportunity to reduce
corrosion allowances, thereby enabling thinner chains to be used in new and
replacement systems. This leads to less weight and therefore less equipment
needed for handling, transportation, and installation, reducing the carbon
footprint of operations. In addition to testing, prior to launch, ICT worked with
a major international operator to complete a technology quali cation project.
Nils Olav Digre, Vice President, Imenco, said: “This technology signals the
start of real change in not only what can be done, but how it can be done, and
it will elevate the potential for cathodic protection to a wider market.”
applications. For buried structures, it can
provide long-term protection over periods
greater than 20 years for applications such
as pipelines. Modern ships are increasingly
ICCP to protect the entire hull.
Combining ICCP with coatings is
often the best way to provide longterm
corrosion protection. Current will
then only ow to defects in the coating,
typically reducing the cost of supplying
an electrical current to just 10% of
that required without a coating. This is
now the standard approach for many
applications, although for ship ballast
tanks and some o shore drilling rigs, the
cost of maintaining coatings is too high.
Therefore, impressed currents are still
sometimes used to protect bare steel.
There are several advantages of
using impressed currents. The voltage
can be readily adjusted to provide the
required protection for a wide range of
applications. It can be made to work even
in highly-resistive soils, and even solid
rock. The status of the protection system
can be readily checked using voltage and
current meters.
Maintenance of the protection system
is carried out predominantly at
recti er stations, and bad anodes
can be easily traced and replaced.
Disadvantages of ICCP include
the need to supply electrical power
and the potential for electrical
interference. It is also possible
to overprotect structures
– preventing passivation,
disbanding coatings or charging
steel with hydrogen.
Cathodic protection is
usually the best way to prevent
corrosion where structures are
constantly immersed in water or soil.
For a cheap and simple solution, sacri cial
anodes remain appropriate. ICCP is often
a more e ective and reliable form of
corrosion protection, where the additional
cost and complexity of a power source
can be justi ed.
REMOTE CONTROL Canadian rm Mobiltex has launched the CorTalk
RMU1-SUB for underground cathodic protection test
station remote monitoring solution. This is intended
to increase and optimise the acquisition of critical
cathodic protection performance and regulatory
compliance data for energy or water pipeline assets,
e ectively removing the need for workers to perform
manual collections in what might be high-risk areas.
A network of battery-powered CorTalk RMU1-SUB
devices transmit data by cellular or satellite networks,
pipeline operators can e ectively eliminate the need to
physically visit CP test stations to obtain critical system
measurements and can begin to leverage near real-time
data collection, the company contends.
The RMU1-SUB has two-way communication
capabilities and can monitor all signals applicable to test point pipe-to-soil
potential, coupon and bond monitoring. By attaching an additional reference
cell, it can capture both on and o DC potentials. By cycling the impressed
current recti ers and galvanic anodes attached to the protected structure,
the device provides a validation of an asset’s protection level remotely.
68 www.operationsengineer.org.uk Winter 2021
/www.operationsengineer.org.uk