How Do Sacrificial Anodes Protect a Hull?
The anode is electrically connected to the steel it protects. In seawater the anode material corrodes first, so the hull doesn’t. The right alloy, the right number of anodes and the right distribution determine how well and how long the hull is protected.
Sacrificial anodes are one part of our cathodic protection for ships and offshore structures.
Zinc, Aluminium or Magnesium?
| Anode metal | Water | Typical use |
|---|---|---|
| Aluminium (Al-Zn-In) | Seawater | Ship hulls and offshore structures; today the most widely used alloy in shipping |
| Zinc (MIL-A-18001K) | Seawater | General seawater use and coated structures |
| Magnesium | Fresh and brackish water | Inland and lower-salinity applications |
Aluminium anodes have about three times the electrochemical capacity of zinc, which is why they are now the most widely used alloy for ships and marine structures. Our pre-casting quality control keeps every element within specification. Zinc anodes follow the US MIL-A-18001K specification. Magnesium has a greater electrical potential difference, so it works better than zinc in fresh and brackish water.
Browse our aluminium anodes, zinc anodes and magnesium anodes. Have a product code? Send it with the quantity and delivery date.
Anode Calculations and Arrangement Drawings
Corrosion protection depends on the right anode distribution and location. On request, we provide anode calculations and anode arrangement drawings. For a replacement, send your existing anode plan or product list. For a new or modified arrangement, the vessel dimensions and operating area are enough to start.
All Ned Marine cathodic protection anodes comply with the recommended practice DNV-RP-B401 for cathodic protection design.
Where Are Anodes Fitted?
- Underwater hull
- Ballast tanks
- Sea chests
- Rudders and thruster tunnels
- Offshore structures
Where the hull shape or space doesn’t suit a standard model, we make a custom anode. A drawing or photo of the mounting position helps.
Standard Types or Custom Shapes
Our catalogue covers standard anodes in many weights and sizes, welded or bolted. For repeat orders, send the part number, metal, quantity and delivery port. For custom anodes, send a drawing, dimensions or a photo of the mounting position. We check stock and production time against your docking date.
How Long Do Anodes Last?
Ned Marine anodes last up to five years. Actual life depends on the alloy, the water, the coating condition and the steel area to protect. We also carry out anode inspections, so you know when to replace them. Docking soon? Send the anode plan or the latest inspection findings and we’ll have the right anodes ready.
Sacrificial Anodes or ICCP?
Sacrificial anodes are the most common choice and the lower investment. Impressed Current Cathodic Protection (ICCP) uses an external current, regulates itself on real-time measurements and can last 20 to 25 years with minimal maintenance. We supply, install and maintain bespoke ICCP systems as well.
Anti-fouling anodes are a separate product: they prevent marine growth such as barnacles and algae. See our anti-fouling anodes.
Ned Marine Supplies Anodes for these Markets
We supply anodes for workboats, cruise ships, port facilities, container ships, car carriers, PSVs, OSVs, FPSOs and offshore energy vessels: shipping, offshore oil and gas, offshore wind, inland navigation and river cruise, shipbuilding and ship repair, dredging, defence, fishing and superyachts.
Anode Quotes: Information needed
- Replacement: product code or photo, metal, mounting type, quantity, delivery port and date
- Custom anode: drawing or dimensions, mounting position, metal and quantity
- Anode calculation: vessel or structure type and size, operating water, existing plan if available, docking date
You don’t need a complete anode plan to ask. We’ll fill in the gaps with you.
Request a quote or an anode calculation: +31 180 420 055 | info@nedmarine.com | Contact form
One Partner on Board
Combine your anode replacement with ROV hull inspections, ultrasonic thickness measurements and NDT and pilot ladders during the same docking. One supplier, one point of contact. ISO 9001 and SCC (VCA) certified.
