Continuous Corrosion Rate Monitoring of Electrical Resistance Probes and Improved Data Accessibility Are Realized Through the CorTalk RMU1-ER


Maintaining an excellent standard of safety and extending asset lifetimes often comes down to having the right data. From strict quality assurance and quality control practices during manufacturing and installation, to monitoring and inspection during operation, knowing the condition of your assets at any given time means getting the most out of them and reducing the chance of unanticipated shutdowns.

Corrosion is one of the most common culprits responsible for early deterioration of pipelines, storage tanks, vessels, reinforced concrete structures, and other metallic infrastructure, but it can be difficult to accurately monitor the extent of damage. Electrical resistance (ER) probes offer a solution; they can portray an accurate reflection of the corrosion impacting your infrastructure providing the integrity information you need to plan maintenance activities. Capable of highly precise measurement, some ER probes are even able to detect changes in element thickness as small as 1 nanometer, meaning you can carefully monitor critical applications where even small amounts of corrosion need to be addressed.


Despite the obvious benefits of ER probes, there are a number of common issues that can arise, largely stemming from the fact that data is manually collected from the vast majority of existing ER probes. Manual collection & review of data is a task often performed alongside other local corrosion field work, such as the periodic (generally annual or biannual) cathodic protection (CP) survey, in order to minimize the labour cost associated with task of manual collection of ER probe data. Taking the data only during an annual survey means that a potentially rich source of data that could provide information around corrosion rates and their seasonal variation is not available to corrosion engineers. The return on the investment in installing the technology could be increased with remote monitoring.  Another common issue is increased opportunities for data quality issues as a result of manual data collection & transfer.

The Solution Brings New Challenges

When it comes to corrosion during operation, knowing an asset’s structural integrity allows you to make informed decisions about its operating parameters and its repair & replacement schedule. The most common methods for monitoring asset integrity as it relates to corrosion are inspections, such as ultrasonic thickness (UT) testing or in-line inspections, and corrosion assessments, such as cathodic protection surveys.

While inspections often give the best picture of remaining wall thickness and any corrosion hot-spots, they are time-consuming and costly. Depending on the inspection technique and the asset being assessed, aboveground storage tank bottoms for example, the equipment may also need to be taken out of service and cleaned, resulting in production losses and other miscellaneous costs.

CP surveys are typically less intrusive than inspections, but they often cannot accurately assess certain areas, such as tank internals or bimetallic systems. CP surveys are also not a good method for assessing the extent of corrosion damage on infrastructure, and can ultimately only judge whether an asset is meeting standard protection criteria at the time of the survey. Additionally, unless a remote monitoring system is also installed, CP survey data cannot accurately reflect changes in protection levels resulting from seasonal dynamics, operational effects such as increased operating temperatures, the addition of or depletion of an inhibitor, or other sources. CP surveys are also capable of assessing the potential for AC interference on a structure or a shorted casing, but as manual surveys are only done periodically, they may not detect problems until after extensive damage occurs.

While there are other corrosion assessment techniques besides CP surveys, such as soil corrosivity testing which can give an idea of the corrosive conditions affecting your assets, inspections are the only way to accurately assess the integrity status of your infrastructure. After inspections, the next most representative technique is corrosion rate monitoring. Corrosion rate monitoring uses probe elements or coupons of the same material as the asset in question, exposed to the same corrosive environment, to simulate the corrosion occurring on the structure. This is most commonly done using ER probes, which can accurately measure the degradation of the probe element throughout their entire service life, giving you a clear picture of the corrosion affecting your equipment.

ER probe measurements can be obtained by manual instantaneous readings, manual download of logged data, or regular transmission of data to the owner/operator via a remote monitoring unit (RMU). Of these three methods, only the RMU provides up-to-date, readily accessible data that can be used to inform owners/operators when there is a spike in corrosion activity.

Instantaneous measurements only give an average of all corrosion which has occurred since the ER probes installation or the last time a measurement was collected. This is because the total amount of material lost between installation and collection times is compared with the original probe element thickness and the intermittent thickness measurements to give an average corrosion rate for the probe over its installed lifetime or since the last measurement was taken. Any number of seasonal or operational conditions can cause a structure’s corrosion rate to change, and instantaneous readings will only provide the average of these, meaning it is unlikely you will be able to pinpoint which changes have increased the rate of corrosion, making it difficult to form an effective response. Another drawback of manually collecting ER probe data is the time it takes for CP technicians to collect the data; manual collection of both instantaneous and logged data means driving time for technicians to & from the ER probe location(s), additional time for permitting, safety, & site-coordination paperwork, as well as the increased risk exposure to employees for driving to & working on-site instead of working remotely. Finally, manually collecting & reporting instantaneous ER probe data can also easily lead to data quality errors as a result of misreporting values on-site, damage to field data collection sheets, or copy errors when moving often handwritten data into a digital final report format.

Reviewing logged data which consists of measurements recorded at preset intervals (commonly collected daily) gives a better picture of changes in corrosion rate over intermittent data collection. Logged data can potentially be correlated to external influences, such as the flooding of a tank berm for example, which may explain increased corrosion of the tank bottom that, if not addressed, could eventually lead to through-wall corrosion and catastrophic failure. This however, may be difficult to trace back if the data is only collected and reviewed annually or biannually; a common practice to minimize costs associated with manual data collection. The infrequent review of logged data also slows the ability of owners/operators to form an effective corrosion response, such as CP system adjustments or the introduction of an inhibitor, if corrosion rates maintain an accelerated rate. However, you can speed up your response and improve your ability to correlate changes in corrosion rate with external influences by pairing your ER probes with an RMU.

Remotely Monitored ER Probes Expands Potential Applications

Expert knowledge of the corrosion rates affecting your assets can help you coordinate outages and address problem areas, thereby preventing unexpected failures and minimizing production losses. ER probes are one of the most cost-effective methods for accurately monitoring asset integrity, and integrating remote monitoring technology with them is the next step toward advancing your integrity program. To address this, MOBILTEX developed the CorTalk RMU1-ER, giving you 24/7 access to accurate, up-to-date corrosion rate data and email notifications if corrosion rate thresholds are exceeded, all through the web-based CorView Cloud Platform. You may want to consider using ER probes paired with the CorTalk RMU1-ER for any of the following applications:

airlift-into-remote-locationRemote Areas: Remote facilities & vast networks which require extensive travel for manual surveillance are an excellent candidate for RMUs. The RMU1-ER can measure and transmit both ER probe data and AC & DC voltage readings, so you can ensure your remote CP system is functioning as intended and your corrosion rates remain low, all without sending someone to collect readings in-person. Keep an eye on all your assets, regardless of how difficult they are to access, by using an RMU1-ER system so that you can access corrosion rate data from anywhere through CorView.

Critical Infrastructure: For any equipment that is process-critical, either for safety reasons or because an outage means halting production, careful monitoring is essential. Continuous remote monitoring of the corrosion affecting pressurized equipment for example, can mean early detection of excessive losses in wall thickness due to corrosion, thus preventing any catastrophic corrosive failure during service. Manual data collection, which introduces a significant delay in response time over remote monitoring, has the potential to allow irreversible corrosion damage to occur for a much longer time before it is detected.

Difficult-to-Monitor Areas: Areas subject to corrosive atmospheres, inconsistent electrolyte exposure, congestion, competing CP systems, or bimetallic systems can all be difficult to monitor. Depending on the exact conditions, ER probes may provide a reliable solution to all these situations. ER probes can monitor corrosion while submerged or exposed to the atmosphere, meaning you can continue to monitor corrosive forces in areas such as tanks with fluid levels that change significantly. CP surveys can also be subject to significant error when there are numerous sources of electrical interference, be that from nearby foreign structures that are not properly isolated or foreign CP systems. By using an ER probe with the same element material as the structure of concern and tying both into the same CP system you can expect they will experience similar corrosive forces, thus giving you a clearer picture of the corrosion affecting your structures even when CP measurements are unreliable.

AC Interference & Mitigation: Easily overlooked by those who don’t know the signs, early identification & mitigation of AC interference can prevent irreversible corrosion damage and can flag dangerous levels of induced AC voltage on pipelines. NACE standard SP21424-2018 states that ER probes can be used to determine if control of AC corrosion on pipelines is adequate according to NACE SP0169 requirements by ensuring a corrosion rate of less than 0.025 mm/year (1 mil/year). It should also be noted that Linear Polarization Resistance (LPR) probes are not considered suitable for AC interference corrosion rate monitoring. ER probes are the ideal choice for gauging corrosion damage as a result of AC interference, and pairing them with the RMU1-ER, which is also capable of obtaining AC voltage measurements, means you can address AC interference & AC corrosion problems before they pose a safety risk.

Pipeline Casings: If your pipeline network has casings installed, they have the potential to create a hotspot for corrosion on your pipeline. Casings frequently trap water near the pipe, creating a corrosive environment that can accelerate corrosion It is also common for them to short to the pipeline, limiting the effectiveness of local CP. In either case, using ER probes with the RMU1-ER alerts you to increased corrosion or changes in the pipeline’s potential so you can address the problem right away. An additional cost-effective corrosion prevention measure can be the use of a vapour-phase corrosion inhibitor (VpCI) in combination with an ER probe. By suspending the ER probe in the vapour phase portion of a casing filled with VpCI, you can determine if the VpCI is being effective, allowing you to remedy the situation by replenishing the VpCI or completing repairs to the system if needed.

Even if your assets are not affected by one of the situations listed above, the RMU1-ER is a great upgrade for saving you time & money while eliminating safety risks associated with in-person data collection and travel to site. Maintain an understanding of the corrosion affecting your equipment with the RMU1-ER by making all your corrosion rate and CP monitoring data easily accessible in a single, safe online location. CorView prevents data errors or losses and allows for faster responses through email alerts if a corrosion rate threshold is reached, or if AC or DC voltage levels change outside acceptable levels.

Realizing the Cost, Safety, and Operational Benefits

The CorTalk RMU1-ER from MOBILTEX puts corrosion rate data at your fingertips, meaning you can rapidly respond to increased corrosion rates caused by changes in environmental and operating conditions or problems with corrosion prevention systems like decreased cathodic protection levels or inhibitor depletion. This solution also gives you access to your asset protection network anywhere and anytime via the powerful CorView Cloud Platform, giving engineers the ability to view and manage all devices and corrosion monitoring data in a single web-based interface that is accessible with any connected device.

Benefits of the CorTalk RMU1-ER:

  • Delivers significant efficiencies and enhancement to your integrity operations when compared to manual, in-person data collection
  • Highly robust and completely autonomous with a typical battery life of 10 years under normal usage
  • Compatible with a wide range of existing ER probe types and manufacturers, so you can integrate remote monitoring for both new and existing ER probes with ease
  • Capable of remotely ensuring your assets meet the NACE SP0169 corrosion rate criterion of less than 0.025 mm/year (1 mil/year).

Contact a MOBILTEX representative to learn more about how the CorTalk RMU1-ER can elevate your integrity program to the next level.

Originally posted by Marc Bracken on LinkedIn

Smiling CP expert with headset and computer beside him


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