Over the Top: Seattle Times describes change in ocean pH from 8.10 to 8.05 as ‘corrosive’

The Seattle Times reports:

U.S. Sen. Maria Cantwell, D-Wash., has taken the lead in Washington, D.C., securing federal support to help Washington’s shellfish industry monitor and adapt to the corrosive seawater conditions and making sure the nation’s top marine scientists are thinking about the next steps.

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20 thoughts on “Over the Top: Seattle Times describes change in ocean pH from 8.10 to 8.05 as ‘corrosive’”

  1. Spent 6 years in a private research and development laboratory. GOOD! Sensible question and I’ll they will never answer it.

  2. A day late and a few bucks short, but the more I read about ocean acidification the more I believe this pH thingy sure be confusing. A half century ago when I started taking chemistry courses I learned that pH was based on conductivity through a glass electrode (hydrogen electrode w/calomel or Ag/AgCl reference) and that dissociation constant for pure water kW =[H30+][OH-] = 10^-14, where [x] is the molar concentration. “pH” was -log[H3O+], making the pH of pure water 7. Any pH [OH-] and was defined as acidic. Any pH >7 meant [OH-] > [H3O+] and was defined as basic. The range works for 1M H+ (pH =0) and 1M OH- (pH=14). Although adding acid to a solution can be considered “acidification” decreasing a pH from 8.2 to 8.15 or even 8.05 does not make that solution acidic any more than adding base to increase the pH from 5.0 to 5.1 makes the solution basic.

    The term “corrosivity” gets tossed around a bunch without really answering the question of “corrosive to what?” Sea water corrodes iron (iron, steel, some stainless steel) among other things because of chloride pit corrosion. If the pH is acidic (<7) the corrosion speeds up. CO2 in aqueous solution is corrosive, hence the market for corrosion inhibitors for boilers and the like. Glass isn't particularly sensitive to strong acid solutions. Mild steel tanks can be used to store 92% sulfuric acid solutions for decades without any serious corrosion, however, they will develop really big holes in them in just a few hours with 30% sulfuric acid in them.

    This whole ocean acidification thing seems to be a blatant misuse of terminology for the purpose of keeping up the AGW skeer, particularly since shell fish seem to survive over a moderately wide range of pH.

    What do I know? I went into organic chemistry where you only have to worry about carbon and hydrogen occaisionaly contaminaed with oxygen and other elements and very seldem was it soluble in water.

  3. Fascinating. I was there once and even had a swim, but did not notice the wreck.

    I suppose now we have a fine example of rust-reinforced concrete.

  4. Perhaps there are no ceramic boats, but they have made sailboats out of Gunnite, a portland cement product.

  5. Once again we turn to Bing Crosby: “…aaacceentuate the positive, eeeliminate the negative…” and you get a pH of 1. Which really is corrosive.

  6. Of course you guys are totally right about the optimal pH. It’s just that in practice, there is such a lot of other factors besides pH. True that water promotes rusting. In some cases, it does so directly. In many others, if not an overwhelming majority, it does so by creating living conditions for iron bacteria.


    The Titanic is a glorious enough research subject and no doubt there are swarms of researchers poking at it as we speak, but if you cared to have a good look at an old rusty car, you’d find iron eaters in it. Water promotes the reaction and it also promotes life, which promotes the reaction even faster. That is why red lead is such a great marine paint (I hope I can say “lead” aloud while the EPA is on shutdown): it is electronegative as well as toxic.

    As far as comfort goes, there is an optimal range but no threshold. There is an extensive discussion of freshwater pH here:


    … with one of the papers quoted claiming: “With few exceptions, pH values between 6.5 and 9.0 are satisfactory, on a long-term basis, for fish and other freshwater aquatic life.”

    But that’s what you’d call usual, customary, and reasonable. For life in general, it can be said there is no uncomfortable pH. There are some interesting extremes:

    http://goo.gl/3Mbcwp (note pH optima in Table 1)


  7. Gene,
    Sea water has many forms of life which live comfortably. Indeed the largest forms of life are in the sea.
    A pH of 8.10 or 8.05 or 8.00 is comfortable for the majority of life on earth.
    Raising the pH towards 14 is increasingly toxic
    It is not sensible to say a lower pH is more corrosive when the pH is more than 7.00
    It is correct to say that an increasing Ph above 7.00 is more corrosive
    Geoff is right to be concerned about scientific ignorance
    Metal rusting is caused by oxygen. Water promotes the reaction.

  8. Howdy Gene
    Dan and I, our throats burned dry…oops, wrong Dan.
    Dan and I are still right about the fact that a pH of 8.05 is less corrosive (less alkali) than a pH of 8.10. Of course you’re right that there are many other components in salt, fresh or even distilled water that are hard on metals.
    Re ceramic ships: I remember the ferro-cement boat hulls of the 1970s. The construction was simple; create a framework of chicken wire, then fill the matrix with cement, rather like stucco on a house but finished smooth instead of rough. Dunno what became of that idea.
    There were a couple of hippies around 1974 who built a boat from a water tank 20ft wide and 40ft tall. Rocked like crazy, according to the reports I read at the time. Last I heard they planned to sail it across the Pacific, but I never heard of them again…

  9. Dan and Geoff: while your theory of the effect of pH on corrosion may be valid in the case of a simple buffer that is not itself corrosive (if such exists), sea water has so much stuff in it (including life) that it will always be too corrosive for comfort, at any pH. There will always be more than enough stuff to react with metals and plastics, and we have not yet figured out ways of building seaworthy vessels with ceramics.

    Heck, even fresh water has enough stuff in it to ruin one’s day. Not to mention distilled water’s ability to dissolve metals (not exactly corrosion in the dictionary sense, but the effect is just as awful).

    In other words, keep your valuables out of water.

  10. What a howler!
    Anybody who has studied basic chemistry knows that water has a pH of 7.0 and is not corrosive. Acids and alkalies have pH above or below the neutral point. The further above or below pH 7.0, the more corrosive the liquid.
    So pH dropping from 8.10 to 8.05 makes the liquid LESS corrosive.
    Equally pH moving from 6.05 to 6.10 would be less corrosive.

    Also worth noting is that sea water has a pH of 8.10.
    Fresh water has a pH around 7.00
    Rain has a pH ranges around 5.00 to 5.60

    Life, including shellfish, exist happily in sea and fresh water and rain is not toxic.
    (Toxic rain contains sulphuric and nitric acids and is polluted.)

  11. Hm. pH is neutral at 7 and becomes more corrosive as you move away, 6.5 being more corrosive than 7 and 8.5 being more corrosive than 8. So a change from 8.1 to 8.05 (I also doubt the measurement, but ad arguendo) would be less corrosive. Is science really this dead?

  12. What instrument are they using to measure this change. I bet it is not repeatable, and varies randomly.

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