Castle Electrodes have been manufacturing and supplying reference electrodes to the worldwide construction and corrosion industry since 1994 and are recognised as the leading supplier in this market sector.

Using high quality materials the reference electrodes are individually manufactured for clients. Over the years a variety of standard electrodes have been developed to meet the needs of customers. The company is also able to manufacture units to comply with specific project requirements.

Electrodes are supplied to customers from all over the world including North America, New Zealand, Taiwan, Saudi Arabia, Poland, United Arab Emirates, Australia, Japan, Europe and the UK. A prompt and competitive service is provided on a worldwide basis.

A supply quotation will be provided within 24 hours of receiving an enquiry and the goods will be dispatched within 3 weeks of order receipt.

Silver/silver chloride electrodes

A range of silver/silver chloride electrodes are supplied. These reference electrodes are true electrodes in the thermodynamic sense and are designed to be used for monitoring steel potentials in reinforced concrete, steel framed buildings and buried steel. The reference potentials for these electrodes are established in accordance with the Nernst equation and as such are affected only by chloride ion concentration and temperature at the element surface.

One of the common problems with silver/silver chloride electrodes used in reinforced concrete is that they have a tendency to dry out due to seasonal changes in the climate. This phenomenon has been eliminated by using a moisture retaining chloride mortar which ensures that the electrode continues to function in abnormally dry conditions which is a unique characteristic found only in these electrodes.

There are currently four standard reference electrodes in the range. They are the LD10, LD15, LD25 and the LD135. The difference between the units is the size, the amount of silver and the area of the measurement interfaces. The most popular units are the LD10, LD15 and LD25 which are used for reinforced concrete and steel framed buildings. The LD135 electrode is much larger and is commonly used for buried installations with a conductive backfill.

After manufacturing the electrodes are calibrated against a saturated calomel standard reference electrode in laboratory conditions and a calibration certificate is issued with each batch of electrodes. Prior to installation it is recommended that a functional check is undertaken by the installer to check that the electrode potentials are stable. Due to the sensitivity of the measurements it is not possible to repeat the calibration procedure on site with any degree of accuracy. It is essential that the installation procedures for the electrodes are adhered to unless otherwise agreed.

The electrodes are made to order so any reasonable cable specification can be met. The standard stock cables are a 2.5mm² copper stranded cable using blue XLPE/PVC sheathing or a 1.5mm² blue high performance cable. If there is any delay in manufacturing it is usually due to an unusual cable specification requirement. Alternatively the electrodes can be supplied without cable but with a spade connector on the silver wire for cable attachment and resin encapsulation on site.

Graphite Electrodes

These are not thermodynamically true reference electrodes and are commonly known as pseudo electrodes. They are not suitable for measuring either absolute potentials or relative potentials over a period of weeks or months. They are designed for the rugged construction environment and have a measurement area of 4000mm² which ensures good contact with concrete.

The reference potential is primarily due to the oxygen reduction reaction and is determined by the amount of oxygen reaching the surface. Also the potential value is affected by the hydroxyl ion concentration in the vicinity of the electrode.

Click here to download Graphite Electrode data sheet.

Seawater Electrodes

Silver/Silver chloride reference electrodes have been used for many years to provide reliable potential monitoring of steel in contact with seawater.

They are often used to monitor catholic protection systems for salt-seawater pipelines and steel structures such as jetties and sheet piling. In seawater the cells assume a potential which is dependent on the chloride ion concentration.

The company supplies a range of electrodes for both permanent and portable use.

The permanent cells are provided in three body sizes.

LD10W 80mm long x 10mm diameter

LD15W 75mm long x 15mm diameter

LD25W 75mm long x 24 mm diameter

The portable unit LD200W is a much larger weighted unit which can be lowered into the seawater to measure steel potentials during monitoring visits.

Combined Potential & Current Measurements

This is a unique CP monitoring unit for buried steel.

This permanent monitoring unit enables the measurement of the steel potential and current flow to an operating CP system. The LD250 is used for buried steel such as storage tank bases and pipelines. A combined unit to measure both absolute potentials and current flows is a significant advancement in CP monitoring which will enable optimal control of the system.

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