Salt water vs. infrastructure

Photo: Michael Tapp

Salt water is still winning. Unfortunately.

Remember back during the Fukushima crisis, when you heard a lot of talk about why the people trying to save the plant didn't want to use sea water to cool the reactors? There were a number of reasons for that (check out this interview Scientific American's Larry Greeenemeier did with a nuclear engineer), but one factor was the fact that salt water corrodes the heck out of metal. Pump it into a metal reactor unit and that unit won't be usable again.

Now, the corrosive power of salt water is in the news again — and this time it's ripping through New York City's underground network of subways and utility infrastructure. I like the short piece that Gizmodo's Patrick DiJusto put together, explaining why salt water in your subway is even worse than plain, old regular water:

When two different types of metal (or metal with two different components) are placed in water, they become a battery: the metal that is more reactive corrodes first, losing electrons and forming positive ions, which then go into water, while the less reactive metal becomes a cathode, absorbing those ions. This process happens much more vigorously when the water is electrically conductive, and salt water contains enough sodium and chloride ions to be 40 times more conductive than fresh water. (The chloride ion also easily penetrates the surface films of most metals, speeding corrosion even further.) Other dissolved metals in sea water, like magnesium or potassium, can cause spots of concentrated local corrosion.

Read the full piece at Gizmodo

Via Tom Levenson

Image: Hurricane Sandy Subway Shutdown New York, a Creative Commons Attribution Non-Commercial (2.0) image from 59949757@N06's photostream


  1. Sounds like an excellent opportunity to invest in rebuilding infrastructures all over the easter seaboard. Imagine the JOBS and GROWTH that could be spurred.

    1. Broken Window Fallacy

      “It’s a tempting argument, really. After all, every time something catastrophic happens, whether it’s a house fire, an earthquake, or a devastating storm, there is indeed economic activity created. Most immediately, the companies involved in recovery and debris removal benefit, often at highly inflated prices given the supply and demand issues involved, as do the people that work for them. However, as I’ve noted before, this is a rather short-sighted argument that ignores the costs that are incurred when a massive disaster like Sandy occurs, not to mention lost opportunity costs of the investments and purchases that would have been made if businesses, homeowners, and the government had not been forced to divert funds because of the destruction that Sandy unleashed on the United States”

      1.  Ah, but it’s not as simple as it might seem on the face of it. Under the entirety of Manhattan island, lay a subterranean layer-cake of aging utilities dating back to as late as the 1880’s. There is a huge workforce of utility contractors and subcontractors that have to be specially trained to know how to patch/fix such old tech in a spaghetti mess of haphazard lines. Training costs money. Disruptions to service cost money. And obsolete equipment abandoned in place underground doesn’t exactly cost money, but it does add to the difficulty of fixing what does work.

        Now, where your counter-argument falls down is this. Saltwater has gotten into all sorts of underground and under grade equipment in NYC. You can spend money to rip it out and replace it with new or re-certified infrastructure/equipment now, and spend MUCH less on maintenance from here on out. (You could also replace what just acts faulty and spend a little more on maintenance.) Or you could do what your “broken window” argument makes you seem like you are advocating, which is do nothing now and wait for it all to fail. And fail it will.

  2. Fun electrochemistry for kids and curious adults: Two coins of different metal, not touching, in a shallow plate of water with a dash of salt. Wait days. Try foreign coins, different salts.

  3. My suggestion would be to drain it and flush it with fresh water (river water would do) several times.  It’s not like anything is going to get any MORE wet than it already has and they’re going to go around and wash most of the stuff off with water anyway.

    1. Did you  miss the part about the irreversible chemical reactions leading to degradation of the entire system?

      We’re going to have to rebuild a bunch of it.  And Chris Christie is going to need to accept federal rail money this time.

  4. Salt water isn’t the same as sea water.  Sea water is way nastier.

    Many companies list different material resistance properties for the two.

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