Re:Hawaii First to Harness Deep-Ocean Temperatures for Power
by sandworm101 on Friday September 04, 2015 @10:15PM
(#10173650)
Corrosion is an immense problem with salt water in large systems. Eliminating dissimilar metals across so many parts is tricky. Even then, unless you're going to plate everything in gold, corrosion will happen. The far easier solution is a heat exchanger between the saltwater and some other working fluid (ie radiator fluid) inside the system. I'm a bit surprised that the hawaii rig is pumping in actual sea water rather than dropping a radiator into the depths. That intake pipe will corrode eventually.
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Re:Hawaii First to Harness Deep-Ocean Temperatures for Power
by dredmorbius on Saturday September 05, 2015 @04:12AM
(#10174277)
Indeed, it is. I think I was vaguely aware of them previously, but I ran across a reference to sacrificial (galvanic) anodes a ways back. Fascinating.
https://en.wikipedia.org/wiki/Galvanic_anode
A galvanic anode is the main component of a galvanic cathodic protection (CP) system used to protect buried or submerged metal structures from corrosion.
They are made from a metal alloy with a more "active" voltage (more negative reduction potential / more positive electrochemical potential) than the metal of the structure. The difference in potential between the two metals means that the galvanic anode corrodes, so that the anode material is consumed in preference to the structure.
Essentially, the galvanic anode is "sacrificed" as corrosion attacks it rather than other bits of your mostly-metal structure in salt water.