unique patented field
system for measuring the rate of corrosion and other parameters of
The U.S.Strategic Highway
Research Program (SHRP) describes the system as giving the corrosion
rate most closely matching the true values.
The system gives important complementary measurements
interpretation of corrosion rate results.
The 'A' sensor measures the corrosion rate and half
The 'B'¯ sensor measures concrete resistivity, ambient
temperature and relative humidity.
Corrosion rate measurement time is 2-5 minutes and up
readings can be stored in the memory for later downloading to a PC.
Weighing only 9 lbs. the system is easy to use,
The Gecor 6™ utilizes the polarization
resistance technique to establish the corrosion rate.
a quantitative measure of the amount of steel oxidizing at the time of
measurement. Up to 100 readings can be stored in memory for later
uploading to a Personal Computer. Relative humidity, temperature,
half-cell potentials and concrete resistivity also can be measured.
Weighing only nine pounds, the system is easy to use, portable and menu
To view videos on the Gecor 6 unit, click on the link below.
Measuring the corrosion of
reinforcement bars polarization technique
Rebar Corrosion and its effects:
Corrosion of reinforcement concrete
affects the safety and durability of concrete structures in the
steel cross section is reduced, weakening the structure.
2. The concrete
is cracked due to the volume increase in rust.
3. The steel to
concrete bond is reduced when cracking and spalling are initiated.
Corrosion is worsened where there is low
concrete cover over the steel, high relative humidity and increased
A true measure of the corrosion rate is
possible using the polarization resistance technique. It has been well
established in the laboratory by Stern and Geary that corrosion current
is linearly related to polarization resistance.
Over a period of four years Gecor 6™ was
developed by several research organizations. The polarization resistance
is measured with a central reference electrode, surrounded by an
external counter electrode. A unique guard ring and external electrode
system confines the area of the rebar tested. This makes the Gecor 6™ the only
field method for determining polarization resistance that is verifiable
with proven laboratory techniques.
Gecor 6™ gives
the corrosion rate (Icorr) which is a
quantitative measurement of the amount of steel turning into oxide at
the time of measurement. The current can be converted into metal section
loss by Faradayā€™s Equation.
Corrosion rate values measured by Gecor 6™ give
precise information on the risk of corrosion and the following broad
criteria have been established:
to 0.5µA/cm2 Low
to 1.0µA/cm2 Moderate
Corrosion rate measurements with Gecor 6™ should
be taken at strategic locations. Other data such as chloride
concentration, carbonation depths or half cell potentials and
resistivity that can also be measured with Gecor 6™, should be
Corrosion rates vary during the life of the structure,
depending on the variations in the concrete
moisture content, the chloride
concentration and the temperature.
Measurements at different intervals should be carried out in
order to get average Icorr
Corrosion potentials can be
taken, and interpreted to give a probability of corrosion. However,
these half cell potential values do not give precise information on the
risk of corrosion. A direct relationship between corrosion rate and
corrosion potential has not been established.
Concrete resistivity of the area
around the sensor is defined from the formula:
RESISTIVITY = 2 x R x D
Where R is the
resistance of a pulse between the sensor electrode and
the rebar network, and D is the electrode
diameter of sensor B.
Concrete resistivity measured by Gecor 6™ is
useful in the interpretation of corrosion rate because it is related to
the moisture content.
>100 to 200k cm Very low
corrosion rate even with high chloride concentration or carbonation.
50-100k cm Low corrosion rate
10-50k cm Moderate to
high corrosion rate where steel is active
<10k cm Resistivity
is not the controlling parameter of the corrosion rate
Since the rate of oxidation is
directly related to the amount of heat energy available, temperature
has a direct effect on corrosion rate. Relative humidity decreases with
increasing temperature, and
resistivity increases with increasing temperature.
Relative humidity influences
the amount of moisture in the pores of the concrete to sustain the
corrosion reaction as well as water run
12 x 8 x
6.5 inches (30 x 20 x 16cm)
9 Lbs. (4kg)
4 'D'¯ type alkaline (24 hours operation)
2 line 16 character display
up to 100 corrosion rate readings
100ft (30m) cable for sensor to meter connection
RS-232 interface cable
for downloading to PC
Constant for Stern and
Geary Equation: 26mV
diameter x .8'¯ (18 x 2cm)
2 Lbs. (0.9kg)
copper/copper sulphate central
2 copper/copper sulphate
confinement sensor electrodes
3 copper sulphate solution
2 concentric stainless steel
1 sponge pad
The meter with 'A' sensor will measure
rate (Stern & Geary law).
Concrete Polarization Resistance
and location of reading
diameter x 1.4 (26 x 3.5cm)
0.6 Lbs. (0.3kg)
copper/copper sulphate reference
1 copper sulphate solution
1 stainless steel counter electrode
state temperature probe 10Ā°C to 80Ā°C
Capacitance relative humidity probe 3 to 95%
The meter with "B"¯ sensor will measure