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4.2 Profometer Corrosion Operation
4.2.1. Preliminary Operations
Prepare the electrode(s)
Rod Electrode -
Before filling, remove the cap with the wooden plug and
soak it in water for about an hour to allow the wood to saturate and swell.
Wheel Electrode -
The wooden plug is not intended to be removed. Im-
merse the wheel in water well before you intend to use it to allow water to
soak into the plug. The felt hoops and the felt hoop connector should be
saturated with water before measuring.
Copper Sulphate (Rod and Wheel) -
Prepare the saturated solution by
mixing 40 units by weight of copper sulphate with 100 units by weight of
distilled water. In order to ensure that the solution remains saturated, add
an additional teaspoonful of copper sulphate crystals into the electrode.
The electrode should be filled as completely as possible with a minimum
of air in the compartment. This ensures that the solution is in contact with
the wooden plug even when measuring in an upwards direction.
NOTE! When handling copper sulphate be careful to take
note of the safety instructions on the packaging.
Selecting the correct grid and marking the surface
One method is to use a relatively large grid for a first estimate, e.g. 0.50
x 0.50 m up to a max of 1.0 x 1.0 m using the coarse grid. (See “4.2.2.
Corrosion Settings”).
Suspect areas can be further investigated using a finer grid (e.g. 0.15 x
0.15 m), to identify the extent of the surface that will require corrective
maintenance.
Vertical elements usually require a smaller grid (e.g. 0.15 x 0.15 m). The
same applies to slender elements, for which the grid will be defined by
the geometry, (e.g. steps, beams and joints etc.).
For large horizontal surfaces (parking decks, bridge decks etc.) a grid of
0.25 x 0.25 m to 0.5 x 0.5m is typically sufficient.
It is recommended to mark out a grid on the surface corresponding to
the grid you wish to use. For small areas where point measurements
will be made with the Rod Electrode this can be done by using a tape
or by drawing the grid on the element. For large areas such as parking
and bridge decks the wheel electrode is preferable. The integrated path
measurement ensures the correct grid in the direction of measurement.
To ensure the correct grid between parallel measurement paths marks
can be drawn on the surface. Please note the 4-Wheel Electrode ensures
a stable parallel grid and requires less marks to be drawn on the surface.
Choosing the appropriate electrode
Depending on the surface under test, it is necessary to choose which
type of electrode will be employed. For small areas or areas that are dif-
ficult to access, the small and light Rod Electrode will typically be used.
For more accessible horizontal, vertical or overhead surfaces, it is much
faster to use the 1-Wheel Electrode. For large horizontal surfaces the
4-Wheel Electrode is recommended for the reason of the significantly
faster automatic measurement in a pre-defined grid.
Connect to the reinforcement
The ground cable must be connected to the reinforcement of the surface
to be measured. This is usually done by chiseling or drilling to the reinforce-
ment. In some cases it may be possible to use existing building elements
that are connected to the reinforcement (e.g. water pipes, earth points). The
connection to the reinforcement should be made with the least possible re-
sistance. To this end it may be beneficial to grind the reinforcement (e.g us-
ing an angle grinder) and to connect the cable with welding tongs. A secure
connection can be also obtained by drilling a 25 mm hole into the concrete
above the rebar, then drill a 4 mm hole into the rebar and insert a self tapping
screw with attached lead into the hole in the steel. The connection should be
tested for continuity. This requires at least one other point of the reinforce-
ment to be exposed and to check the resistance between the two with an
Ohmmeter. The connections should be situated as far as possible in oppos-
ing corner areas of the surface under test. The measured resistance should
not be more than 1
Ω
above the resistance of the cable used.
