A cost effective corrosion detection and monitoring solution

What is it? BonPEC is a state of the art Pulsed Eddy Current technology innovation designed and engineered by BonPhysics BV.

It is a non-intrusive electromagnetic technique based on Pulsed Eddy Current which allows detection, measurement and monitoring of corrosion in low alloyed carbon steel pipes and vessels through their insulations, coatings, paints, concrete fireproofing or marine growth. The technology does not require direct contact, cleaning or special and specific preparation of the surface of the object to be examined, therefore no costly and unnecessary insulation removal is required to perform the PEC examination with a considerable cost saving for the client.

PEC is the efficient and cost effective solution for the examination of insulated and corroded components and parts in the on- and offshore industry and in the energy sector.

Corrosion Under Insulation (CUI), Corrosion Under Fireproofing (CUF) and Flow Accelerated Corrosion (FAC) as well as Well Integrity are typical PEC successful applications, solutions and benefits. PEC performance is effective also for semi-contact measurements carried out with dirty, rough, cold and high temperature objects.

The working principle

BonPEC is based on Pulsed Eddy Current (PEC). It measures the decay time of the pulsed eddy current induced in the object under examination. This pulsed eddy current is induced in the material by means of a DC current circulating through the sending coil circuitry of the BonPEC probes. This DC current generates a magnetic field that takes a while before getting uniform and stable. The magnetic field lines generated are closed lines and move through the insulation and the ferromagnetic object under examination. At the moment the current is cut off, the sending coil stops generating the magnetic field. During this transient, pulsed eddy current is induced in the ferromagnetic object under examination. This eddy current migrates and decays through the object wall and rapidly extinguish when it reaches the opposite object side. Eddy current is a circulating current and it generates during its decay a variable magnetic field. Its field lines move through the sensor. BonPEC measures the resulting decay of the magnetic field versus time which is a function of the object thickness and of its material electromagnetic properties.

Schematic representation of the pulsed eddy currents migration through a carbon steel object.

The figure above represents schematically the decay of the induced pulsed eddy current through a carbon steel object wall. The  pulsed eddy current measured signal is presented in a double logarithmic graph: the horizontal axis represents the time in milliseconds (ms) and the vertical one the measured signal amplitude (µT). Characteristic of this signal is the presence of a bending point that indicates the induced eddy current decay time.

At this time the eddy current reached the far surface of the object and rapidly disappears (signal drop after bending point). This time is called TAU (τ) and it is a function of the material magnetic permeability (µ), of the material electrical conductivity (σ) and of the square of the object average thickness (d) in the footprint area, and it is given as τ = µσd2 (see figure above).

Reference measurement

BonPEC needs no reference blocks for the examination set up and calibration. The reference block is the object under examination. Before starting the object examination, a reference measurement is needed. The reference measurement will give per definition an average wall thickness (AWT) of 100% and its signal will be compared with all other measurements. The reference measurement shall be taken on a good object part and/or on the thicker location in an area free of appendances and uniform in thickness. When possible, the reference measurement shall not be adjoining cell measurements with a variance larger than 2% of the reference thickness, the edge of a grid, intrados of an elbow or blank cells where obstructions are present. The reference measurement shall not be taken on sheeting overlap or near obstacles.

At the end of the survey, during its evaluation, the reference shall be verified and if a thicker and more uniform area with good signals will be identified, then the reference location will be replaced with the best signal within this area.

Accuracy and reproducibility

The measurement accuracy in normal operating conditions is +/- 5% of the reference value under the condition that the AWT reduction of the measurement is not less than 50% of reference value (100% and thicker area of the object) and that its lift-off variation does not exceed +/- 50% of the reference value lift-off.

The reproducibility of the tool at a single location is about 2% under the same condition of AWT and lift-off variation mentioned above. Field experience in a monitoring situation showed that keeping track of the exact measurement locations is of major importance; as paint can be washed away and the insulation or sheeting material is not necessarily fixed to a location on the pipe.


BonPEC is a screening tool and a qualitative inspection technique: it gives real time information about the status of the insulated object in order to discriminate the areas of interest on which to perform a deeper survey.

No direct contact and special surface cleaning is required to operate BonPEC. This non-contact characteristic makes it possible to detect corrosion on high temperature surfaces without many probe adaptations. A simple thermal shield protects the probe from extreme temperatures allowing measurements up to +500 ºC. Above this temperature the reduction of the magnetic permeability in the object reduces the reliability of the pulsed eddy current signal.

There is no need to remove insulation or coating, which reduces cost and increases the inspection speed. Coupling the signal to the object is not critical and it allows the technique to be used under uncommon circumstances.

Corrosion and scab

Piping with corrosion scabs

BonPEC is also effective in measurement through corrosion product and scab (figure above). To perform these measurements a dedicated algorithm and an additional lift-off between the probe and the surface of the object under examination has to be applied to reduce their interference. Corrosion products and scab have a magnetic permeability similar to that one of the carbon steel base material of the object under examination but they have a lower electric conductivity. By applying this additional lift-off the pulsed eddy current signal generated in these corrosion products and scabs will get weaker than the response of the pulsed eddy current signal generated in the object based material, allowing the detection of the remnant Average Wall Thickness (AWT).


Depending on the lift off and the average wall thickness of the object to investigate, a choice must be made which probe to use to optimize the reliability of the results. For a large lift off a large probe is needed. Two probes are directly available P0.5 and P1.0, another probe for even larger lift off is under development. The applicable range of each probe depends on the material properties and measurement geometry, most important the lift off and average wall thickness. In the graph below you can see the selection diagram for a carbon steel flat plate:

and for a 2” outer diameter carbon steel pipe:

The corresponding footprint for each probe are shown in the below picture:


The ‘AWT’ represents the Average Wall Thickness footprint and the ‘DWT’ represents the footprint for the Defect Wall Thickness algorithm.

BonPEC probes are designed to minimize false readings, hence they are insensitive to metal objects near the probe, except for the object that is right below it. Because of this focusing the probes are (within boundaries) insensitive to the lift-off, angle mismatch or thickness of the sheeting. These are all important for measurements in the fields that reduce false calls and increase effectiveness of data interpretation as the signal when acquired is robust against these changes.

Typical Applications of PEC

Listed below are all the typical applications for PEC measurement methods, that the method of BonPEC applies to as well.

Corrosion Under Insulation (CUI)

The most common insulated objects in a plant consist of pipes and vessels. It is important to monitor and control the integrity of these parts to assure continuity and avoid un-expected breakdowns.

BonPEC can  be successfully applied for the detection of CUI which is one of the most common degradation mechanism for insulated pipes and vessels in plants.

Corrosion under fireproofing (CUF)

Generally when a Spherical Tank goes out of service for maintenance, most NDT and inspection activities are focused on the Pressure Vessel body. The support legs are also important components and they contribute to the global integrity of the Spherical Tank. Examination of the legs is mainly a visual examination of the outside fireproofing.

BonPEC allows for a good evaluation of the integrity of Spherical Tank Support Legs through its fireproofing. When the support legs are not considered or not good examined, there may be serious consequences for the integrity of the structure that may collapse during a water test prior to its going back to service (see the image). Water is generally heavier than the liquefied gas product stored in this Pressure Vessels types.

Flow Accelerated Corrosion (FAC)

Flow Accelerated Corrosion (FAC), also known as flow-assisted corrosion, is a degradation mechanism in which a normally protective oxide layer on a metal surface dissolves in a fast flowing fluid. The underlying metal corrodes to re-create the oxide, and thus the metal loss continues until eventually the remaining wall thickness is insufficient to contain the internal pressure and rupture occurs.

Many pipe failures caused by FAC have been reported in power plant piping systems. Under certain water chemistry, fluid velocity, and operating conditions, FAC can cause internal wall thinning of condensate and feed water piping, heater drip and drain lines, and other carbon steel piping. In some cases, this thinning has led to catastrophic failures and fatalities.

This image shows the Mihama accident damage in 2004. FAC typically occurs in the temperature range of approximately 80°C to 300°C and is commonly found in economizer tubing, low pressure evaporator tubing, drum internals and feed water systems. In addition, the propensity for forming FAC damage is greater in areas of high turbulence, mostly in elbows and its damage may extend to the straight pipe section up for approximately a length of 1 pipe diameter upstream and 2 pipe diameters downstream.

In-service corrosion monitoring

PEC measurements are generally highly repeatable. This makes it well suited for corrosion monitoring purposes. Corrosion rates can be deduced from wall thickness measurements over a time interval at fixed locations.

For example, PEC corrosion monitoring was recently installed to the test on a refinery furnace outlet operating at 420°C. The asset owner discovered that an inappropriate material had been used in the construction of the elbows of the outlet, which led to unacceptable high corrosion rates. Measurements at two-week intervals confirmed the expected corrosion rates. The high reproducibility of PEC readings at one spot allowed the asset owner to quickly and accurately monitor the degradation of the plant over time.

Inspection of heavily corroded equipment

Another application of PEC is in-service assessment of heavily corroded pipes and vessels. Often, safety considerations do not allow the corrosion products to be removed on stream. In this case, PEC has the crucial advantage that it can be applied without disturbing or even touching the corrosion products.

Offshore risers, caissons and offshore structures

PEC is the cost effective solution to examine the Splash Zone area of raisers, caissons and offshore structures. The Splash Zone is the most aggressive corrosion area, see the graph below and the location in the image at the right.
PEC can easily measure through the riser coating and through the Monel protective metal layer detecting corrosion in the carbon steel section and through the marine growth layer.

Operation is generally performed with rope access and divers. To increase safety and to reduce risks, PEC measurements can be deployed remotely mounted on a riser tool. Different riser tools have been developed with diameters from 15” up to 50” in Australia and in Europe.

Steel Sheet Piling

Steel Sheet piling are commonly present in harbours, channels, sluices and dams to protect this facilities. They are particularly common in The Netherlands where approx. 40% of the territory is below sea level and where waterways and port areas have a very high economically value.

Corrosion and degradation of Steel Sheet Piling is a continuous deterioration process that may lead to serious safety, economical and legal consequences for Port and Waterways Authorities. If not monitored and controlled during their service life, serious degradation can be expected after only 10 years of operation for example due to accelerated degradation processes such as Accelerated Low Water Corrosion (ALWC), a form of corrosion caused by microbial growth that can occur on inshore, tidal, marine, steel piled structures. Its consequences can be expensive, often requiring costly remedial works and unplanned facility downtime. Corrosion rates in excess of 3 mm/year have been observed and if left untreated can results in the integrity of the facility being seriously compromised.

Corrosion degradation of these structures may be also as consequence of high-low tide, fresh and saltwater mixing and it may be more aggressive in the Splash Zone due to the higher concentration of Oxygen. Damages can also be mechanical due to ship movements and impacts.


Visual examination and UT verification are traditionally used for the examination and inspection of Steel Sheet Pilings. PEC is a cost saving alternative solution for screening and monitoring these structures:

  • PEC screening supports the prioritisation of the maintenance actions and, the proper and effective allocation of the available maintenance budget and resources where they are exactly needed.
  • PEC monitoring will gain long-term financial savings in maintenance versus the possibility of a complete replacement or reconstruction, which is very significant.



The Software

The software program designed for BonPEC, facilitates the interpretation of the decay signal for a user defined measurement grid.

The program is based on the way that a typical NDT survey is performed. Initially one needs to know what needs to be investigated, which is represented by client and object parameters. Important parameters are the kind of object (pipe, plate or
bend), the nominal wall thickness, the lift off and the type of cladding used. Based on this information and the experience of the operator, a suitable probe is selected and a suitable scan is defined. After a reference measurement is performed and the complete survey is done, it can be saved. Ater the survey is saved it is possible to export the data in a convenient format for manipulations in other software systems. The program gives tools to inspect, check, evaluate and report the measurement data.

The program can be used in different password protected modes. The simplest mode is ‘Client’, where the measurement results can be accessed and investigated only. The normal mode is ‘Operator Level 1’ mode, which gives all needed functionality to perform a typical NDT survey. The ‘Operator Level 2’ mode enables the adaptation of some of the graphical
features (like colours, fonts and sizes) and the creation of adapted probe settings. Further it enables the possibilities to perform ‘Monitoring measurements’. ‘Operator Level 3’ is for the advanced operators and the ‘Superuser’ mode gives full program control of all algorithm and probe settings. See the following table for further specification of the software belonging to the different modes:

For an example of the userguide belonging to Operator Level 3, click here.

A very important feature of this software program is the possibility of automatic reporting. It is capable of providing you with an automatic generated document of your choice (word or excel). See below for a snapshot of such a report:

The benefits of using this software at a glance:

Software benefits

  1. Fast data collection;
  2. Direct real-time interpretation and results;
  3. Data digitally stored;
  4. User-friendly operation (touchscreen);
  5. Advanced PEC signal presentation feature;
  6. Advanced PEC data analysis and evaluation algorithms (footprint minimum WT value, etc.);
  7. Advanced reporting features (Auto report generation, Graphs, 3D result projection on object model/photo, etc.);
  8. In-service corrosion monitoring;
  9. Interface language user dependent;
  10. Operator level dependent software and training.

To operate BonPEC a dedicated training is mandatory to learn how to operate the equipment and to improve efficiency during a BonPEC examination. The training takes 5 working days and it include a theoretical and practical examination. Training is available in the The Netherlands but it may be also organised at location.

BonPhysics BV delivers equipment, training and support, offering tailor-made solution and advices to all leases. We can therefore develop together new client specific application of the technology design to answer to the specific client’s needs. This may require the design and development of new probes or implementation of new software applications.

License Agreement

The BonPEC equipment and technology is available through a 3 year license agreement that includes updates for hardware and software, business continuity and interesting short renting solutions to answer to the peak shaving of your business and operation excellency. The license agreement offers operation to perform and be up to date with the latest BonPEC development.

BonPhysics BV is continuously looking to new opportunities and different agreement solutions. An hybrid agreement consisting of an hardware sale in combination with a software license is one of the alternative solutions that offer the possibility to investment for the hardware while the software is licensed for the period of 3 years. During this period software updates will be included while any hardware upgrade will be at a market price at that moment in time. At the expiry of the 3 year software license, client will be free to operate the equipment and any BonPEC update and upgrade will be available at market price.

We offer you:

  • More than 25 years’ experience with PEC technologies and applications;
  • Effective Tailor made solution answering to your specific needs;
  • Full assistance and support during license period.
The Team

Riccardo Scottini worked as an application engineer for Incotest, and was the driving force for Sonovation (SONOPEC). Since the beginning of this century, he and Victor have been working together on PEC technologies. He is now pushing the PEC technology development further with BonPEC.

Victor de Haan founded BonPhysics in 1997. He observed a growing need for outsourcing Research and Development activities and in the meanwhile, the company exist for 25 years. Moreover, Victor has been developing PEC technology for more than 20 years.


Reasons for you to join the BonPEC user community

  1. Access to know how and more than 27 years of experience of BonPhysics B.V. – PEC team;
  2. Realtime data transfer and interpretation is possible;
  3. DWT (Defect Wall Thickness) measurement options – minimum wall thickness within footprint of the probe;
  4. CUI through galvanised sheeting is possible;
  5. The capability of in-service corrosion monitoring;
  6. There is an operator level dependent software and training available;
  7. Accessibility and availability of new software and hardware innovation and releases;
  8. Moreover; Hardware and software made by BonPhysics BV enables:
    • Miniaturized electronics;
    • Tailor-Made solutions;
    • Application development in cooperation with you or other clients.
History and Future of Pulsed Eddy Current

The basic pulsed eddy current principle was known for a long time, but ARCO (Atlantic Richfield Company) was the first one who applied it for wall thickness measurements. ARCO named the inspection equipment “TEMP®”, as acronym for “Transient Electro Magnetic Probe”.

ARCO TEMP® equipment (1987)

ARCO was an American chemical company that needed a system for detecting corrosion under insulation. After a development period they applied the system successfully in Alaska for their own purposes. ARCO patented the principle and approached a few NDT-companies who might be interested in this NDT inspection method. The method was proven but needed further development. Shell and RTD were one of the selected companies that received a system for trials.

Shell and RTD worked both to the improvement and innovation of the ARCO-TEMP tool.

Due to the fact that many customers were confused by the name TEMP®, associating it with a temperature measuring technique, RTD decided to change the name TEMP® into RTD-INCOTEST® (an acronym for INsulated COmponent TESTing) while Shell named their equipment PEC which stands for Pulsed Eddy Current. The INCOTEST was developed by RTD during a cooperation with BonPhysics that started in 1997.

In 2015 the PEC technology has been transferred from Shell Global Solution to TR Sonovation.In 2016 TR Sonovation initiated the PEC technology innovation Road Map with SONOPEC which is no longer available.In 2023 BonPhysics supplies the market with BonPEC providing a cost effective system using new sensor technology.

What about the future? We hope to improve the BonPEC technology, so that measurements can be conducted as well in the case of non-magnetic steel (SS, Alu, Cu, etc.). We hope to reduce the footprint by developing more sensitive sensors. Besides, we will work on absolute probes, so that no reference measurement will be needed anymore. Finally, we aim to integrate the hardware in the probe, and update the software in such a way that it will automatically filter and detect defect.

Contact us!

Are you interested in our product or services? Or are there any questions left?

Please, feel free to contact us!

Phone number: ++31 (0)78 676 7023
Email: victor@bonphysics.nl
Address: Laan van Heemstede 38, 3297 AJ, Puttershoek, The Netherlands


What does PEC stand for?

PEC is an acronym for Pulsed Eddy Current.

What is BonPEC?

BonPEC is the cost effective solution for corrosion detection and monitoring of insulated components in the Oil & Gas and Energy sectors.

What type of inspection method belongs to BonPEC?

It belongs to the Eddy Current inspection method.

What is the basic working principle of BonPEC?

BonPEC is based on the Pulsed Eddy Current principle (PEC).

What is Pulsed Eddy Current?

Pulsed Eddy Current is Eddy Current induced by suddenly switching of a constant magnetic field, therefore Eddy Current generated in this “transient”.

What is BonPEC designed for?

It is designed for detection and monitoring of Corrosion Under Insulation (CUI).

What are the primary applications of BonPEC ?

Insulated, fireproofed, coated, or encrusted vessels, columns, storage tanks, spheres, pipe, ship hulls, offshore platforms and wells.

What are the BONPEC primary limitations?

Applicable only on Carbon Steel and Low Alloyed Carbon Steel.
(Depending on the available probe) In presence of coating and/or stainless steel weather proofing cladding nominal wall thickness 2 – 70mm, stand-off/insulation 0 – 250mm, diameters 2” up to flat plates.

When the weather proofing cladding is Aluminium, then the minimal detectable Average Wall thickness is approx. 3 mm at 20ºC and it is function of the temperature.

When the weather proofing cladding is Ferromagnetic, then the general equipment performances and application range are halved (WT < ~35mm, LO < ~100mm).

Can you inspect non-ferrous materials with BonPEC?

No, at present BonPEC is restricted to ferritic material of Carbon Steel and Low Alloyed Carbon Steel. However, development of BonPEC for non-ferrous materials is nearing completion.

Can BonPEC inspect through fireproofing, or refractories and if so is there any limitations?

Yes and the limitations are the same as the primary limitations. A ferritic steel wire mesh will not affect a reading but reinforcement rods will do, therefore a minimum of 4” mesh size or pattern is required.

What are the temperature limitations of the base object material for a BonPEC inspection?

-100ºC to +500ºC

What types of insulation and cladding can BonPEC inspect through?

The insulation type need to be non-magnetic and non-electrical conductive. The weather proofing cladding/sheeting can be Aluminium, Stainless Steel or Galvanised ferrous material, for the latter sheeting type the general performances are halved.

Is there a dead zone for a BonPEC probe?

There is a “dead zone” which depends on the coil minimum time of each probe. The bigger the probe size, the stronger the received signal and the larger its coil minimum time.

What does the coil minimum time affect?

It affects the minimum detectable Average Wall Thickness (AWT).

How much coverage does BonPEC typically have on an elbow, pipe, etc?

This is corrosion mechanism dependent and the grid size may be adjusted for straight pipe to 100% coverage depending on the corrosion characteristics. Elbow’s intrados area is accessible by placing the PEC probe orthogonally to the flow.

Does ice have any effect on BonPEC– cryogenic service?

Ice does not have an effect, as it does not influence the generated magnetic field.

Does BonPEC need external power supply to be operated?

No the BonPEC equipment is powered by Battery Packs.

Is BonPEC intrinsically safe?

No this system is not explosion proof and may have the potential to cause a spark, if a connection or wire is broken.

Can BonPEC tell the difference between a mechanical disturbance and an artefact of corrosion?

Yes the technician has the ability to view the raw signal or data in real time and evaluate the influence of surrounding objects.

Can BONPEC differentiate between internal and external corrosion?

Under Laboratory condition with constant lift-off it is possible to determine whether an indication is internal or external by observing the registered signal amplitude.

In field operation, insulation does not have a constant thickness and therefore it will not be possible to discriminate whether an indication is internal or external.

Does the product inside a pipe affect the BonPEC data?

When non-magnetic and non-electrical conductive it will not affect the data.

Can BonPEC differentiate between internal and external corrosion?

Under Laboratory condition with constant lift-off it is possible to determine whether an indication is internal or external by observing the registered signal amplitude.

In field operation, insulation does not have a constant thickness and therefore it will not be possible to discriminate whether an indication is internal or external.

Is BonPEC sensitive to Stagnant Vs. Moving waters?

Water will not affect BonPEC results as long as it does not penetrate inside connectors and the probes coils. However, vibrations in the object under investigation, need to be prevented as much as possible as it reduces the applicable wall thickness and Liftoff range of BonPEC.

Is the BonPEC technology sensitive to internal and external coatings? Which ones?

The system would see an influence from any magnetic of ferrous coating and the application would be evaluated for prior history or if further testing would be required.

Is BonPEC sensitive to internal lining materials?

When non-magnetic and non-electrical conductive, BonPEC will not be sensitive to internal lining material such as: HDPE, FRP or Non-Ferrous Claddings.

Is a calibration block needed to set up the BonPEC equipment and to perform the inspection?

No calibration block is required to perform the inspection; calibration or reference measurement is performed on the component to be tested or on a sample having the same material parameters as the object to be inspected.

Can BonPEC detect pitting corrosion?

BonPEC is not designed for detection of localized pitting and holes. It is designed for generalized corrosion detection. When pitting is grouped and not localized, then it may give reliable indication.

Can BonPEC inspect welds, preferential weld corrosion?

BonPEC  is not a weld inspection tool.

Does a BonPEC inspection need to be verified by other NDT methods to validate findings?

The principal validation method is UT. BonPEC is a relative inspection method which compares the reference data signal with all other measurements. As a result it gives an Average Wall Thickness variation in the object. During validation of the findings, the Reference location and the larger deviations should be checked over all footprint area. It should be noted that within the footprint, the local Wall thickness could be thinner than the given Average Wall Thickness.

What is the BonPEC Footprint?

The footprint is the magnetized area on the inspected object. The induced Pulsed Eddy Current decay will give the Average Wall Thickness value compared to the Reference.

What is the BonPEC equipment accuracy?

The general BonPEC measurement accuracy is 5 % of the reference value and this will be valid when the local wall reduction will not exceed more than 50% of the reference WT and when the lift-off/insulation variations will be within 50% of the reference lift-off.

What is the BonPEC equipment repeatability?

The general equipment repeatability deviation is ±2%.

What is the BonPEC equipment detectability?

Detectability depends on the indication and footprint size. To be detected an indication must have a surface extension of more than a third of the footprint area and the volume deviation to the reference area must be more than 10%.

Can BonPEC detect lamination?

Lamination is not affecting the reading.

Do weather conditions affect the BonPEC system performance?

The ambient electromagnetic field could be affected during severe storms, and therefore affect the generated magnetic field and the measurement.

Although the system is well sealed it is electronic equipment and in severe weather, shelter may be required for the computer and transmitter/receiver, with further sealing requirements of the sensors even to the point of requiring BonPEC subsea probes.

Does vibration / harmonics from rotating equipment have an effect on BonPEC?

Yes, all moving ferritic objects within the generated magnetic field will affect the reading. Their influence depends on the received signal strength. How stronger the received signal how weaker is the influence of vibration.

What effect does the insulation and cladding have on the BonPEC data/readings?

Insulation and cladding increase the lift off and hence the footprint. Cladding with magnetic properties enlarges the integration or magnetic footprint area.