RetroLink™
Aluminum anode retrofit string for shallow-water structures

In 2009, RetroLinks were used to retrofit the cathodic protection on over 120 structures in the Gulf of Mexico.

RetroLink is a cost-effective cathodic-protection retrofit system consisting of 3 to 15 aluminum anodes cast directly onto a heavy-duty wire rope. The RetroLink attaches mechanically and electrically above the water line, allowing the string to hang in the seawater with at least two anodes dragging in the mud. The installation is almost always diver-less and performed from a small vessel. RetroLink can be used for any structure in less than 85 feet of water.

Dependable - In addition to being easy to install, the RetroLink system is incredibly robust. RetroLink is consistently able to resist category 2 hurricanes and often remains in service after category 4 storms. Two operators doing post-hurricane inspections in 2009 found that 95% of their RetroLinks were still working after hurricanes Gustav, Ike, Humberto, Rita, and Katrina. The RetroLink is exceptionally reliable cathodic protection with minimal installation expenditures for offshore, inshore or marine structures.

Extremely versatile - The RetroLink is designed to hang from a support that is welded or bolted to the structure. When the string is attached, it hangs with the anodes submerged. With two anodes trailing on the bottom, sea movements are attenuated and the string won’t wrap around the structure. The RetroLink can be hung from any horizontal or vertical member and can be attached subsea if necessary.

Adjustable in the field - The wire-rope core provides electrical conductivity through the anode system as well as sound mechanical support. The strings have up to fifteen anode segments, which may be cut to length (often in the field) and deployed to provide cathodic protection exactly where it’s needed. If additional anode material is laid in the mud, the system life can be extended to almost ten years. Links can be stored on the boat and cut to length and installed as necessary, especially during post-hurricane inspections.

Applications

Shallow-water offshore structures

Many offshore structures sitting in less than 85 feet of water can have the CP replaced very cost-effectively using the RetroLink system. No diving is required. The system can be installed quickly with a small topside crew and can provide five to seven years of protection. RetroLinks have been used on everything from single-pile caissons (pictured) to shallow-water four-pile structures.

Offshore wind turbines

Foundation piles may be placed up to a year before the transition structure is installed. During this period, RetroLinks can provide protection for the existing portion of the structure. They can be recovered and redeployed during periods of grid power interruption.

Docks, harbors and wharves

RetroLink systems are reliable and easy to maintain using small under-dock access vessels and equipment commonly found around such installations. A simple design guide enables the facility owner to apply adequate levels of cathodic protection following a simple field verification procedure. In the past, links have been installed to provide cathodic protection to multiple bridge pilings, both reinforced concrete and steel.

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Key design points

Modular design

The modular concept allows for a simple design. Depending on the salinity of your water, select zinc or aluminum anode material. Zinc anodes are recommended if water is less than 12‰ of full strength seawater (4.2 ppt Cl). For all other applications, aluminum RetroLinks are recommended.

Leader assembly

For above-water suspension, use PVC-coated wire rope for corrosion resistance. The modular design allows hang elevations to be easily adjusted in the field.

Weld-on or clamp-on support

The weld-on topside suspension assembly can be affixed to horizontal or vertical members. The isolator can have links for protecting offshore risers. Links can be attached subsea using a modified hang-off. A new clamp-on support is also available, complete with I-Clips to prevent crevice corrosion.

Hurricane-resistant

As of January 2009, Deepwater recorded 668 RetroLinks installed on 112 structures in the Gulf of Mexico. Since Hurricane Gustav, twelve of these structures have been inspected for CP readings. Eleven are still protected; one is low.

Quality control

Deepwater draws anodes from two local affiliate foundry locations, allowing us to strictly regulate QA/QC for all the aluminum and zinc anodes we use in our systems.