GMC published bulletin archive. Original bulletin wording is preserved below; illustrations are for context.

Backfill compatibility

GMC Electrical, Inc. does not and will not bag our “Staperm” Reference Electrodes in gypsum, bentonite, and sodium sulfate. The reason is all three (3) of these items will contaminate the reference electrodes causing the potential stability to be compromised. Agricultural gypsum used in anode backfill is not pure and has a high level of iron which will contaminate the reference electrode. Bentonite used for anode backfill has a high level of aluminum which also contaminate the reference electrodes. Sodium sulfate will contaminate the cupric sulfate when used in reference electrodes.

GMC’s published backfill approach

GMC Electrical, Inc. bags all our “Staperm” Reference Electrodes in a non-polarizing backfill consisting of a pure analytical grade calcium sulfate type plaster which does not contain any chemical elements which will contaminate the reference electrode. This backfill will allow a reference electrode to maintain a potential of excess of 30 years. GMC Electrical, Inc. has been manufacturing reference electrodes of these types since 1984.

Thank you for using GMC “Staperm” Reference Electrodes.

GMC published bulletin archive. Original bulletin wording is preserved below; illustrations are for context.

Marine growth

1. Heavy sea growth on electrodes (not being cleaned by divers).

Salinity changes

2. Seawater salinity change (lower than normal seawater salinity) due to fresh water intrusion i.e. rivers and estuaries.

Monitoring circuit connections

3. Reference electrodes connected to monitoring system or SCATA System without opening reference electrode circuit completely. High impedance circuits will cause electrode to load up over time and damage the electrode.

*NOTE: Monitoring units must completely open the electrode lead circuit by way of electronic switch or relay or electrode damage will occur over time.

Chemical contamination

4. Chemical contamination of electrode from contaminated seawater due to contaminated environment.

Water circulation

5. Electrodes being placed in reference chute without enough holes or slotting for proper fresh seawater circulation and water in chute becomes stagnant with built up contaminates.

GMC published bulletin archive. Original bulletin wording is preserved below; illustrations are for context.

Understand the installation environment

Historically corrosion testing, corrosion surveys, cathodic protection design surveys included soil analysis testing, for corrosive soils which included PH, Sulphates, Chlorides, Fe and many other contaminants. These analysis tests are not only for the determination of the corrosivity of the soil but also can be utilized for the determination of the type and location for proper placement of reference electrode. Reference electrodes are delicate instruments and should be treated as such. Reference electrodes should be installed in proper soils to mitigate contamination and possible failure from contamination. Any soil / electrode issues can be avoided if proper corrosion soil analysis practices are followed.

GMC’s published recommendation

GMC Electrical, Inc. recommends that in areas where permanent electrodes are to be installed, that a simple soil analysis performed to determine the proper type of electrode to be used and the proper location.

GMC published bulletin archive. Original bulletin wording is preserved below; illustrations are for context.

Background

When monitoring systems first came on the scene for monitoring pipeline corrosion and cathodic protection potentials problem soon started to develop regarding the failure of the permanent reference electrodes. The blame of the failures was put upon the electrode manufacturer. This was not an isolated failure event all electrode manufacturers were experiencing these same failures.

Research and development

In the late 1990-2000 GMC Electrical, Inc. was involved with a company in designing their new monitoring units for the corrosion industry. This company designed and built their unit based on GMC’s design parameter’s regarding the electrode sensing circuit, through testing, research and development. GMC Electrical, Inc. determined that the major factor in the failure of the permanent electrodes in the past with monitoring systems was due to the loading of the electrode, allowing the electrode to be driven as a cathode in a dissimilar corrosion cell circuit; this allowed the metallic electrode element inside to polarize. The existing monitoring systems at the time did not open the sensing circuit after the readings were taken. Even with the extremely high impedance of these circuits it still allowed the electrode to be under a load, polarize and fail with time.

Sensing circuit design

The electrode sensing circuits were designed for new monitoring units to allow for complete disconnecting (open circuit) of the electrode test leads after reading was taken.

Published requirements and warranty statement

GMC Electrical, Inc. must emphasize the importance of the proper sensing circuits utilized in any monitoring system whether web-based of SCATA type; they must have a circuit that completely opens the reference circuit after reading are taken. If monitoring units attempt to only utilize high impedance circuits in the reference circuit any electrode of any manufacture will eventually fail, due to electrode loading over time. It must be noted that if monitoring systems are utilized that do not have reference circuits that completely open the test circuit while the unit is at rest or asleep GMC Electrical, Inc. cannot warrant the electrode and any and all warrantees are null and void.