OFFSHORE & MARINE
Corrosion Protection for Marine Environments
The HMS Samarang, a 28-gun teak Atholl-class frigate, received the first known application of cathodic protection in 1824, when Sir Humphry Davy fitted iron and zinc plates to her copper hull to stop the copper sheathing from corroding in seawater. The fix worked almost too well: the now-protected copper stopped releasing the copper ions that had been keeping barnacles and weed off the hull, and biofouling became the new problem. Two centuries later, the same electrochemistry protects a much larger scope of assets, platforms, pipelines, hulls, moorings, and desalination intakes, across every stage of exposure from the tidal zone down to the seabed. What changed is the standards, the alloys, and the scale: modern offshore CP systems are engineered to governing codes like DNV-RP-B401, built for multi-decade service without a diver ever touching an anode. From shoreline to deep sea, the anode strategy still comes down to the same variables Davy was working with: what alloy, how much current, and how long it needs to last.
Splash Zone Exposure & Alloy Selection
American Carbon anodes run on jetties, piers, offshore platforms, subsea pipelines, floating storage units, and desalination intakes along the North American coast, and each asset type sets its own exposure profile. The one most specifications underestimate is the splash zone: tidal pilings and jacket legs that cycle between wet and dry corrode faster than sections that stay fully submerged, because wet-dry cycling reintroduces atmospheric oxygen to the metal surface every tide, and oxygen availability drives the corrosion rate. Galvanic CP current only moves through an electrolyte, so a splash-zone structure is protected only while seawater is actually in contact with it, the dry portion of every cycle gets no current, which is why splash zones typically pair CP with a coating or corrosion allowance rather than relying on anodes alone.
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Below the splash zone, seawater resistivity sets the alloy choice. Seawater runs roughly 20-30 ohm-cm, versus soil, which is commonly in the thousands of ohm-cm. That low resistivity lets aluminum and zinc anodes push high current at low driving voltage, which is why BADGERCOAST Galvanic Anodes in zinc or aluminum are the offshore default rather than magnesium, magnesium's higher driving voltage has nothing to overcome in a conductive electrolyte and just burns the anode down faster than the design life calls for.
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Offshore systems built to DNV-RP-B401 are typically sized for 20-25 years without a diver replacing an anode, so on jacket structures and larger platforms where galvanic current alone can't carry the load, ACC pairs BADGERCAST High Silicon Cast Iron Anodes with an impressed current system engineered to that same design life.