Featured

January Featured Product Model UT

The environmental conditions beneath an aboveground storage tank make it very difficult to obtain potential measurements. The sand is dry when the electrode is first installed. Cathodic protection currents and/or heat from the product further dries out the sand sharply increasing resistivity. A permanently installed reference electrode can completely dry out in this environment and the absence of moisture in the area will prevent it from rewetting. Consequently, electrodes in such locations may last only a few years. Where potential measurements throughout the life of an AST are desired, a preferred solution is to use our Undertank Reference Electrode (Model UT).

The Undertank Reference Electrode is placed in a slotted pipe installed in the sand pad beneath the tank bottom. When bottom potential measurements are needed, the electrode is slowly pulled through the pipe to produce a potential profile. An alternate design with a threaded coupling rather than an eye-bolt can be used in those cases where it is necessary to push the electrode into the pipe. Between measurements, the electrode can be either left at one end of the slotted pipe or used to develop a potential profile in another tank.

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Featured

November Featured Product Model TE

The potential across a tubesheet under cathodic protection can show large variations from one location to another. Areas with excessively electronegative potentials can cause hydrogen damage to titanium or ferritic stainless steel tubes. Other areas may have potentials insufficiently negative to adequately protect the tubesheet. These potential gradients cannot be detected by a reference electrode mounted on the side wall of the waterbox. EDI’s Model TE Tubesheet Mounted Reference Electrode is designed to mount any place on the face of a tubesheet. They are shipped with a double tube plug which is inserted into the end of a condenser tube and tightened. The electrode’s lead wire terminates in a waterproof connector which plugs into a mating connector on the lead wire which has been affixed to the tube sheet face. This attachment system allows the electrode to be easily removed during scheduled outages. You will find more info here Model TE

December Featured Product Model FE

The Model FE Process Vessel Reference Electrode is designed to operate in environments where ordinary reference electrodes cannot survive. These include elevated temperatures, high pressures and/or contaminated electrolytes. This is a two-piece unit consisting of a bridge which is permanently installed at each location where potential measurements are desired and a separate reference electrode. Because the reference electrode is a separate piece, it is isolated it from the aggressive environment which substantially increases its service life. The reference electrode can also be removed for calibration or service without affecting the integrity of the vessel.

For intermittent readings, the reference electrode is simply pressed into the bridge. In this case, a single reference can be used with several bridges. When continuous readings are required, the reference electrode is threaded into the bridge. Reference elements available with this product are gelled copper/copper sulfate or gelled silver/silver chloride. You will find more data here Model FE

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EDI CEO, Jim Diamond will be guest speaker

Jim Dimond, President of Electrochemical Devices, Inc., will address the Western New York corrosion committee on Thursday December 13th at 10 AM. The meeting will be held at:

Leisure’s Restaurant
6001 Big Tree Road
Lakeville, NY 14480
WebSite: http://www.leisuresrestaurant.com/

Title: Coupon Technology – An Overview

Jim will address the reason for using, where to use, and where to not use Cathodic Protection Coupons. He will discuss installation procedures as well as proper interpretation of data collected from Cathodic Protection Coupons. He will explain advantages of the Concentric Coupon with emphasis on the elimination of an IR component even where there are local current sources. He will explain interrupting CP current with a magnetic switch.

Prior to becoming President of EDI, Jim was president of Dimondale Co. Inc. which designs and manufactures cathodic protection products. Previously, he oversaw reference electrode manufacturing for Harco, Inc. He has over 40 years’ experience in cathodic protection including product design, manufacturing, and field engineering.

Electrochemical Devices, Inc. (EDI) was founded in 1986 and specializes in the design and manufacture of a variety of products for monitoring and controlling corrosion, including cathodic protection coupons. They provide the concentric coupon and a magnetically operated switch to connect the coupon and structure.

TN 1 How to measure tube sheet potentials

The potential across a tubesheet under cathodic  protection can show large variations from one location to another. Different waterboxes of the same apparent design can produce different potential distributions. Areas with excessively electronegative potentials can cause hydrogen damage to titanium or ferritic stainless steel tubes. Other areas may have potentials insufficiently negative to adequately protect the copper alloy tubesheet. These potential gradients cannot be detected by a reference electrode mounted on the side wall of the waterbox.

EDI’s Model TE Tubesheet Mounted Reference Electrode is designed to mount any place on the face of a tubesheet. They are shipped with a double tube plug which is inserted into the end of a condenser tube and tightened. Tube plugs are available for common tube sizes between 5/8 inch and 1-1/4 inch. The electrode’s lead wire terminates in a waterproof connector which plugs into a mating connector on the Model TW wire which has been affixed to the tube sheet face.  This attachment system allows the electrode to be easily removed during scheduled outages.  For additional information, visit EDI website.

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October Featured Product Model CM

Our Model CM reference electrode can be used in all types of concrete structures. When this electrode is used in seawater applications, where the chloride level of the pore water is expected to remain nearly constant, it functions as a reference electrode providing stable reproducible potential readings. When used in other structures in which the chloride level can vary slowly over time, Model CM provides short term stability suitable for depolarization measurements. Its small size makes it suitable for embedding in the grouted annular space behind piling wraps.
You will find more data here Model CM

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NACE Corrosion Technology Week

EDI will be represented at NACE Corrosion Technology Week (16 SEP-20 SEP 2018) by John Olson. It will be held at the Royal Sonesta Hotel in the Galleria section of Houston, TX.

If you have questions for John about corrosion control monitoring or the use of monitoring products that the company offers, he will be at most of the STG 05 and STG 35 meetings that week.

If you are unable to attend NACE Corrosion Technology Week, visit our website for information about EDI products. Contact information is at the bottom of our homepage.

September Featured Product Model UC

Our Model UC concentric coupon is designed to make potential measurements that are substantially free of IR-drop error without either interrupting current or disconnecting the coupon.  The potential measuring port is located in the center of the coupon, well away from IR drop fields in the environment. Concentric coupons are preferred for locations where interrupting currents or disconnecting the coupon to make measurements is not practical. They are particularly well suited for use with remote monitoring units.

EDI’s concentric CP coupon is typically installed at the base of a test station since access through a soil tube is needed for making potential measurements. This product may also be ordered with a contained packaged zinc reference electrode which eliminates the need for access through a soil tube and a 1 sq. cm. coupon for measuring AC current density.

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TN 21 Maintaining Liquid Filled References

Portable, liquid filled, reference electrodes must be cleaned and refilled regularly.  The copper sulfate solution contains dissolved oxygen.  Oxygen gradually reacts with the copper to form copper oxide which shifts the potential of the reference.  The more copper oxide the greater the shift.  Potential shifts of up to 10 mV in a week’s time are possible.  This problem can be prevented by cleaning and refilling the reference electrode regularly (preferably weekly but at least monthly).  The newer gelled filled portable reference electrodes do not have this problem since the element and gel have minimal contact with the atmosphere.

Another problem occurs on reference electrodes that have a ceramic tip.  The insulating tip is porous so that the copper sulfate solution will leak through and allow conductance.  If the tip dries out, the holes can become partially plugged with copper sulfate salt which increases the electrical resistance through the reference.  The process is progressive, with the resistance increasing a bit more with each dry-down until, eventually, the tip becomes fully insulating (totally resistive).  Boiling the ceramic tip in distilled water for an hour or two will restore it.  A similar problem to this occurs when the ceramic tip becomes plugged with either dirt or oil.  When this happens, the ceramic tip should be replaced.

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TN 20 Potential Errors in Concrete

A common source of error encountered when making potential measurements in or through concrete is junction potential; this topic has been discussed in Technical Note 19.  There are additional sources of error in concrete potential measurements.  The mobility of all ions in concrete is retarded due to the material’s cellular microstructure.  Consequently, concrete has high electrolyte resistivity so the presence of any internal current flowing through it will be marked by relatively high IR drops.  Sources of these internal currents are often corrosion currents from corrosion of rebars.  The associated IR drops become incorporated into corrosion potential measurements and can result in a several hundred millivolt error.

Errors of the same magnitude have been documented for measurements made through concrete, such as to a structure buried beneath a concrete slab.  In a detailed study on this topic1, potential measurements were made on buried tanks at nine different service stations in the northeast.  When the measurement was made with the reference electrode contacting the concrete slab, the potential was from 20 to 260 mV more negative than when the reference electrode was directly contacting the soil through an access hole.  The rectifier was off during these measurements to eliminate CP currents as a possible error source.  In the same study, potential measurements were made on a pipe located beneath an airport runway.  Measurements made through the concrete near the edge of the runway were about 200 mV more negative than the same measurement made through the grass adjacent to the slab.  Wetting both the concrete and the grass did not significantly change the measured values.  Clearly, measurements of buried structures should never be made through concrete without using a soil contact access port.

  1. B. Husock, “Techniques for Cathodic Protection Testing Over Airfield Pavements,” US Air Force Report CEEDO-TR-78-31, Tyndall AFB, FL, July 1978.

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