Civil Engineering Reference
In-Depth Information
Environment
Application
Durability/Life
Comments
Thermal
sprayed zinc
Marine or
anywhere (with
humectant)
Requires
bulky spray
equipment and
skilled operator
Greater than 10
y life expected.
Reduces with
severe exposure
Colour change
to concrete is
only effect
Thermal
sprayed Al/
Zn/In
Marine and de-
icing
Requires
bulky spray
equipment and
skilled operator
10-15 y marine
exposure, 15-
20 y in northern
de-icing
Colour change
to concrete is
only effect
Adhesive zinc
sheet
Not for very
high wetting.
Will work
in very dry
conditions
No special
skills apart
from soldering
connections
Design life is
25 to 50 years.
Gel deteriorates
in very wet
conditions
Anode is 1-2
mm thick.
Either leaves
zinc metal
finish or painted
metal finish
Encasement
jacket
Marine only,
mainly columns
and piles
Special skills
required for
grouting up
jacket
Very durable.
Life up to 50 y
Pile column
section enlarged
by 25 mm or
more. Load
increase.
Repair can be
structural
Probe anodes in
cored holes
Anywhere
No special
skills
15 to 25 y life.
Very durable
Core holes
at 330 to 650
mm centres.
Requires good
design
Probe anodes in
patch repairs
Any patch
repairs
No special
skills
10 to 15 y life.
Very durable
Only area
around
patch repairs
protected
maximum of 750 mm spacing around a patch. Approximately 200,000
sold protecting about 100,000 m
2
of concrete at the end of 2002.
•
Probe anodes in cored holes - Potted-up zinc anode approximately 45
mm diameter by 40 or 60 mm long. Installed on 330 mm to 650 mm
spacing in 50 mm diameter cored holes (other shapes and sizes are now
becoming available).
4.2.2 The merits and limitations of galvanic cathodic protection
The principle advantage of galvanic cathodic protection is its simplicity, with
no power required.
1
In principle this could lead to cost savings on a range of projects.
2
Its strength is also its weakness. The simplicity means there is no
way of controlling it and there is no automatic flow of information
