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borna godaz

manufacturer of cathodic protection anodes

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Reference Electrodes

Friday, 08 March 2019 00:00
  • Reference electrodes

The potential of underground pipelines and buried installations in soil or immersed in water is measured relative to reference electrodes (hallfcells). Reference electrodes are divided into three main categories depend on application such as: oil, gas and petrochemica and marine:

v Copper / Copper sulfate reference electrode (portable & permanent) for using in soils including Cl-

v Zinc / Zinc sulfate reference electrode (portable & permanent) for using in soils including Cl-

v Silver / Silver chloride reference electrode (portable & permanent) for using in marine environments

v Zinc Reference electrode for using in marine environment

The potential difference of different reference electrodes relation to hydrogen standard electrode at 25 ° C is as follows According to BS 7361:

 

Electrodepotential (V)
Cu/CuSO4+0.32
Ag/AgCl/KCl saturated+0.2
Ag/AgCl/Seawater+0.25
Calomel/KCl saturated+0.25
Zn/Seawater-0.78

 

  • Copper / Copper sulfate reference electrodes

Cu/CuSO4 BORNA Godaz reference electrodes are produced in two procedures, portable & permanent. The portable type Equipped with Probe is suitable for many applications, while the permanent type is used on the floor of the tanks and in proximity of smart trans-rectifiers.
Dimensions of reference electrode might be chosen according to application, while surface area of ​​this electrode in contact with the CuSO4 solution must be large enough in order to prevent polarization problems during the electrochemical tests. The copper electrode must be selected from high purity copper (99.9%). Afterward, Cu/CuSO4 electrode submergs in saturated copper sulfate solution in order to remove and cleaning of all oxides and greases. It is essential that the saturated state of the solution be maintained by adding extra solid copper sulfate. The electrical connection of the portable reference electrodes to the environment is created only by the porous layer of the electrode head. So the moisture of electrode is maintained by diffusion of copper sulfate solution.

 

 

Cu CuSO4 portable rederence electrode bornagodaz.jpg

 Cu/CuSO4 portable rederence electrode

 

 

Also, The electrical connection of permanent electrodes to environment is created by the entire porous clay body. So, the moisture of around electrode is maintained due to the presence of backfill which is usually containing 75% gibson, 20% bentonite and 5% sodium sulfate). Design of these reference electrodes can be observed according to below figures:

 

 

Permanent Cu CuSO4 reference electrodes suurounded with backfill.jpg

  Permanent Cu/CuSO4 reference electrodes suurounded with coke breeze

 

  • Zn/ZnSO4 Reference electrode

Utilization of Cu/CuSO4 electrodes in soils containing chloride ion is not possible, Since Zn/ZnSO4 reference electrodes are used instead of Cu/CuSO4 electrodes. These electrodes are structurally similar to Cu/CuSO4 reference electrodes completely. The main difference is immersion of zinc electrode in a saturated zinc sulfate solution with high purity.

 

  • Ag/AgCl Reference electrode

BORNA Godaz silver / silver chloride reference electrode has been founded by a silver elctrode which its surface is coated with silver chloride by thermal or electrolytic processes. The most important feature of this electrode is high degree of stability. This electrode is directly used in seawater or brackish river waters. Also, this electrode is used In other applications, such as steel in concrete structures.
these electrodes are placed in a container for mechanical protection due to application of them in seawater environment. Therfore, the holes are created on these compartments in order to establish of contact with the electrolyte. These electrodes should be immersed in seawater for several hours before usage. Also, end of electrode cable are insulated to prevent short circuits. It should be noted that These electrodes must be kept in a potassium chloride saturated solution when they are not used.

 


Ag AgCl Reference electrode.jpg

  • Zinc reference electrodes

Perhaps using a metal reference electrode does not seem logical with aim of measuring potential differences in direct contact with electrolyte around the structure, While Zinc reference electrode is suitable for many applications specially in sea water. This reference electrode is more economical than Ag/AgCl reference electrode. So it can be used instead of Ag/AgCl electrode unless a high degree of stability is required.
high purity zinc ingot (at least 99.9% Zinc with 0.0014% iron as maximum content) is used in manufacture of zinc reference electrodes. KYNAR cable (HMWPE/PVDF) is used as a resistant material to chloride and sulfate ion for connection with a cross-section of 10 mm2 or 16 mm2. Also, this cable is welded to steel core inside the electrode. The connection point between the copper cable and steel rod is coated with epoxy resin. It should be noted that accuracy of the potential measurement by using Ag/AgCl electrode in sea water is about ± 5 mV while it is about ± 30 mV by using Zinc reference electrode in sea water
.

 

Zinc reference electrodes bornagodaz.jpg

The following documents show typical datasheets of Portable and Permanent Reference Electrodes made in BORNA Godaz company.  Also, Other informations such as Potential measurement reports according to NACE RP0196 and BS 7361 Standards have shown here.

 

Technical Documents of BornaGodaz Reference Electrodes (Portable and Permanent HalfCells):

Datasheet Sample of BornaGodaz Permanent CuCuSO4 Reference Electrode According to BS7361 Standard

Datasheet Sample of BornaGodaz Portable Cu-CuSO4 Reference Electrode According to BS7361 Standard

Datasheet Sample of BornaGodaz Permanent Zn-ZnSO4 Reference Electrode According to BS7361 Standard

Datasheet Sample of BornaGodaz Portable Zinc Reference Electrode According to US-Military 18001J Standard

Datasheet sample of BornaGodaz Portable Ag-AgCl Reference Electrode According to BS 7361 Standard

Potential Test Report of BornaGodaz Permanent Cu-CuSO4 Reference Electrode - Approved by Corrosion Laboratory of Metallurgical Research Center

Potential Test Report of BornaGodaz Portable Cu-CuSO4 Reference Electrode - Approved by Corrosion Laboratory of Tarbiat Modares University

Potential Test Report of BornaGodaz Permanent Zn-ZnSO4 Reference Electrode - Approved by Corrosion Laboratory of Tarbiat Modares University

BornaGodaz Reference Electrode Catalogue (Permanent and Portable HalfCells)

Contact us

02156233930-02156233929
02156232587-02156236590
02156230236
 [email protected]
Tehran Province, Shamsabad Industrial City, Golbarg Number 2

   

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Bornagodaz

BORNA Godaz Company was established on the path of development of BORNA Electronic activities in the field of cathodic protection in 2004. ...

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