Australian built and U.S. owned warship corroding from salt water.

[Rodney Mills]

I think this might be of interest to 'Olde Salts", small pun intended Cheers, Rodney

Brand New” Aluminum Ship: Foiled by Seawater

By Mark Thompson | @MarkThompson_DC | July 5, 2011 | +

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USS Freedom (top) and USS Independence / Navy photos
101104-N-0000X-002 WASHINGTON (Nov. 4, 2010) A composite photograph of the littoral combat ships USS Freedom (LCS 1), top, and USS Independence (LCS 2) provided by Naval Surface Forces, U.S. Pacific Fleet shows the two ships underway. (U.S. Navy photo illustration/Released)


You can’t make this stuff up: the Navy concedes the first vessel in its latest fleet of warships — the 18-month old USS Independence (not to be confused with the late aircraft carrier sporting the same name) — is suffering from “aggressive” corrosion. Both the Navy and the ship-builder say it’s no big deal, and to be expected when steel and aluminum components slosh around together in salt water. Like in an ocean, for example.
The Navy, eager to keep its fleet numbers up, is now buying two competing versions of these so-called Littoral Combat Ships. The planned $37.4 billion buy of 55 of the corvette-like (3,000-ton, 75 crew) vessels emphasizes coastal warfare instead of the blue-ocean mayhem their bigger brothers and sisters — frigates, destroyers, cruisers and aircraft carriers — are built to fight. Unfortunately, the first LCS built by (Australian-owned) Austal Ltd. in Mobile, Ala., is an aluminum-hulled trimaran that has been corroding into the sea. “I’m surprised it happened so early,” naval scholar Norm Polmar told Bloomberg News. “This ship is brand new.”
The Navy says the problem is manageable, and, besides that, Austal says, it’s the Navy’s fault (it also issued a painful-to-read statement suggesting it’s nothing new). Both agree such teething problems aren’t unusual in a new class of vessels. But the salt-water rot could give foes of aluminum vessels a weapon. “It gives fodder to people who for so long have said that buying an aluminum ship would be problematic for the Navy,” Jay Korman, of the Washington D.C.-based Avascent Group, told the Mobile Press-Register, the shipyard’s hometown paper. “It’s a perception issue as much as structural issue.”
Of course, it may be tough for Austal’s competitor — a Lockheed-Martin led (but Italian-owned) team building a steel-hulled LCS in a Wisconsin yard — to brag: its first ship, the USS Freedom, suffered a major crack in its hull during sea trials earlier this year. Maybe when they fix these ships the Navy can rechristen them: the USS Independence From Corrosion and the USS Freedom From Cracking.



Read more: U.S. Navy’s “Brand New” Aluminum Ship: Foiled by Seawater | U.S. | TIME.com

[john sutton]

this problem could be caused by electolysis which is the result of electical action attacking the least noble metal which in the above case would be the aluminium.
Its a common problem in marinas in this part of the world caused by leaking electrical currents-Usually results in wasting of bronze skin fittings and propellers.john sutton

[vic mcclymont]

Why not fit sacrificial annodes? that would solve the problem

[Ivan Cloherty]

Why not fit sacrificial annodes? that would solve the problem

Guess they already thought of that Vic, but unfortunately it doesn't work on aluminium. Served on a ship with steel midship house structure with an aluminium bridge structure to aid stability on increased cargo capacity, only problem was that the aluminium (in those days 60's) could not be welded to steel, so had to be riveted with steel rivets, which wore the holes in the aluminium bridge housing as the vessel worked in rough seas, also set up a corrosion around the holes making the whole navigation bridge suspect, not a nice feeling when heaving around in a heavy sea, wondering if you were going to part company with the rest of the ship. Tried using aluminium rivets but the steel in the housing snapped them as the vessel worked in rough seas. Also thought they had learnt something from the Falklands conflict when the aluminium bridge structures on the frigates (again for stability purposes) just melted in the heat of the fires when they were hit by exocets, so the RN said they would reconsider use of aluminium in any UK warships. Whether or not a decision was made to exclude it on all vunerable structures was ever enacted I do not know, perhaps one of our NAVY shipmates may know.

[Peter F Chard]

Just a thought and seeing that these vessels have been built in the US -- did they use the correct grade of aluminium ?? It is critical that a marine grade is used. Also, the anodic protection has to be absolutely right or the hull will corrode, and it is essential that copper based antifoul paints are NOT used anywhere on the hull. Cheers Peter in NZ.

[Tony Morcom]

You wouldn't believe it possible in 2012. They never had these problems in the 1800s when ships were still made of wood. And they call this progress

[happy daze john in oz]

Very true Tony, but they did have a breed of worm that slowly ate away the wood. Same problem different era??

[happy daze john in oz]

Interesting that now mnay of the newer cruise ships have the superstructure made of an ali/steel compound but though it makes the total weight less it still corodes.

[Tony Wilding]

The SS United States has a corrosion problem with her superstructure at main deck level, a major problem for preserving her, *Steel rusts, Aluminium * breaks down, Wood rots and *GRP suffers from Osmosis if the Gel Coat is damaged and underwater, *i think Sea Water can be more harmful than fresh, *something called Electrolosis *is created, *especially between different metals, *steel ships in fresh water last for years with little corrosion, *lots of the Swiss, German and Italian *Lake Paddle Steamers are almost 100 years old., * the RN found Aluminium *no suitable because of its low melting point, *have no idea of the lifespan of a modern Cruise liner *with the amount of it used in there construction.

[j.sabourn]

Why build with steel anyway. Why not plastic or cement. There must be special forms of this nowadays. Doesnt matter if a ship is made of steel this is no protection from the sophisticated weaponry, one hit and theyre gone in any case. Minehunters are not built with steel. Cheers John Sabourn