MATCOR Sea-Bottom™ Marine Anode Sled

Marine environments can be some of the harshest environments on the planet for corrosion of steel structures. Indeed, the earliest application of cathodic protection can be traced back to Sir Humphrey Davy and the British Navy’s investigation into corrosion on copper sheathed wooden vessels. This video demonstrates MATCOR’s impressed current sled anodes that are successfully being used to protect steel piles for jetties, docks and other similar steel structures in marine environments.
The MATCOR sled anode consists of two or more Mixed Metal Oxide tubular anodes housed in durable Schedule 40 PVC pipes with concrete end caps. Manufactured at MATCOR’s ISO 2001:2015 certified facility in Chalfont, Pennsylvania in the USA these anodes have been used to protect marine piling structures from Florida to Alaska to Indonesia. These anodes are available in a wide range of configurations and outputs and ship ready to install without any field fabrication required.
This trade show model illustrates how the sled anode impressed current system operates. The structure being protected in this model is fabricated from coated steel tubes not much different than many marine piling support structures. Here we have a working model using a quarter inch MMO coated titanium rod anode protected inside a PVC housing with holes to allow the anode to be in contact with the seawater electrolyte. The sled anode lead cable is connected to the positive terminal of a small DC power supply. The steel structure is connected to the negative terminal of the power supply. A copper-copper sulfate reference electrode is strapped to one of the piles for testing the pile potential.
With the power supply off, we can measure the native potential with no current applied to the structure. With the system completely off, the native potential is negative 770millivolts. After energizing the power supply and adjusting the output to approximately 2 amps, we can measure the ON potential of the structure, which in this is negative 1840 millivolts. Interrupting the power supply yields an instant Off potential of negative 1200 millivolts. This is the polarized potential of the structure and meets both the 850millivolt OFF criteria and the 100 millivolt polarization criteria.
MATCOR has successfully installed many cathodic protection systems to protect steel piles for jetties and other Marine Structures. Take this Jetty structure in Indonesia.
This jetty is constructed with four interior rows of concrete piles and an exterior row of 247 bare metallic piles. They are driven into the seabed to a depth of 15m with 6m in the water, and they are covered with a concrete cap. Initially the jetty owner was looking to install galvanic aluminum anodes to protect the steel piles. Lets run some numbers.
Using industry accepted standards, our engineers calculated the total current required to initially polarize the structure and also the current required to maintain polarization. Based on that we were able to calculate the total mass and quantity of anodes required for the desired 30 year service life. A total of 374 aluminum anodes each weighing 200 kg would be required to be installed. Each of these anodes would need to be welded to the structure using professional divers trained in underwater welding.
MATCOR suggested an alternate approach using the Sled Anode Impressed Current system. The use of sled anodes significantly simplified the installation reducing costs and offering a much safer installation.
Each of the 6 anodes are shipped with integral cables and an orange floating marker buoy. The anodes have lifting pads cast in the concrete to allow for future removal of the anodes for any dredging operations that might be required.
Each anode was rated for 175 amps continuous service for 30 years; however, the actual operating output required to meet NACE Criteria was less than 120 amps each, assuring an even longer anode life.
The actual installation took only 3 days. You can see the sled anode being lowered by an onshore crane. The anodes will be located at approximately 8m depth.
The six sled anodes on this project were connected in pairs to one of three oil cooled Transformer/Rectifier units installed on the Jetty. These rectifiers are rated for 45 Volts and 375 Amps of DC Current Output. Once commissioned and given several weeks to sufficiently polarize the jetty structure, a MATCOR NACE CP 3 certified engineer visited the site to perform testing to confirm the proper operation of the cathodic protection system. The results taken from multiple test points along the length of the jetty using a portable reference electrode confirmed that the jetty was meeting the NACE standard with an off potential reading exceeding negative 850 millivolts.
For more information, visit matcor.com/sledanode

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How much percent is the system loaded? What is the current consumption per section after 72 hours?