XCorr Corrosion sensors

Corrosion, in one form or another, can cause high value assets to deteriorate, shortening their useful lives. Corrosion related repairs and replacements drives up costs. Thus Condition Based Maintenance (CBM) strategies are being explored by many organizations in an effort to reduce inspection costs while minimizing the risk of equipment damage from corrosion. Aginova provides several tools to help in scheduling maintenance.

Coating degradation (CDS)

orrosion Protection Compounds (CPCs) or paints are routinely applied on military assets for prevention of corrosion. When exposed to the elements (water, light and salt) these coatings degrade and therefore have to be reapplied. Typically these are applied at fixed time intervals that can sometimes be too soon or too late. The CDS measures the coating degradation in terms of impedance (measured in ohms) and phase angle.
Therefore CDS can be used to determine the condition of the coating. The photograph above shows a sensor head developed by SwRI® which when coupled with the appropriate electronics measures the coating impedance. The photograph shows a complete packaged solution using CDS, T and RH.
SPECIFICATION
Impedance range* 100 ohms to 10 Mohms.
Phase angle 0 to -90.
Frequency range 100Hz to 105Hz.

Water detection (WLS)

Number of wetness cycles as well as the corrosivity of the environment can be measured using the IDS. The photograph to the left shows a corrosivity sensor where one of the electrodes is copper and the other is an iron-chrome alloy. A DC potential is applied across the two probe leads and a current response measured. The ratio of potential to current is inversely proportional to the corrosion.
When both electrodes are made out of the same material such as copper the sensor detects the presence of moisture and can be used to measure the number of wetness cycles. The sensor can be used to measure corrosivity or detect moisture. The IDS sensor in combination with Temperature and RH gives a better picture of the corrosivity of the environment.

SPECIFICATION
Fixed potential applied and resistance measured.
Resistance range – Two orders of magnitude.

Corrosivity measurement (MAS)

Multi Array Sensor probe is a passive electrochemical sensor where there is no applied voltage. As an immediate benefit, there are no issues associated with sensor control. It is a true corrosion rate monitor able to measure uniform and localized corrosion.
This MAS probe sensor is unique in that it does not rely on electrolyte solution to bridge the gap between the probe elements (although electrolyte must be present at anode and cathode sites). Each element is connected together through a common wire within the electronics package.
In this manner anodic (corrosion) and cathodic sites can develop at the elements as on an actual metal. A typical circuit to measure the low currents is shown in the figure to the left. Note MAS probe is the only sensor in the market that can measure pitting corrosion.

Damage Assessment (DAS)

Damage Assessment Sensor (DAS) is perhaps the simplest of all, and requires the monitoring of a property that is related to the volume of material present. It is similar to an ER probe, a coupon like specimen is utilized, but this specimen is position where the resistance to current passing through the coupon is measured (typically a wire).
As the wire corrodes, it’s conductor cross sectional area decreases, causing the resistance to rise. This elevation in resistance can be tracked over time to yield corrosion rate. ER probes are sensitive to other factors which influence resistance (Temperature), and must therefore be accounted for. Eventually, the wire coupon corrodes through and no current is passed. The damage assessment sensor builds in redundancy to the electrical resistance sensor by simultaneously monitoring a multitude of wires each with a different thickness. As the smaller diameter wires corrode through, a definitive “calibration point” is measured with which to check the crude measure of corrosion rate.
This sensor has been tested in the laboratory. Field trials are planned in Q4 2007. More details will be provided after the field trials.

Ultrasonic Wall Thickness measurement sensor

Aginova is developing a new generation of Wireless Wi-Fi® Ultrasonic Wall Thickness measurement sensors. The sensors can operate on a pipeline at up to 300°C in continuous operation (ambient temperature outside pipe).
It becomes now possible to:

• Continuously monitor thickness of pipes
• Suppress human intervention
• Access unreachable pipelines
• Get a correct picture of the pipelines corrosion state