Thursday, August 18, 2011

Answer: What is this thing in the middle of the street?

So... what IS an "anode" anyway?

If you do something like:

[ define:anode

you'll see it's got something to do with an electrochemical system.  In particular, an anode is an electrode through which electric current flows into a polarized electrical device.  Great.  What's that got to do with an anode in the middle of my street?

I decided the simplest strategy was to do the obvious search:

[ anode in street

 which in turn led me to read an article on "Design Information and Guide for Corrosion Control of Steel Used for Underground Installations."  It's not a catchy title, but it gave me a big clue: the article discusses something called "cathodic protection of underground metal" by using a "sacrificial anode."

After poking around on various version of anode queries for a while (including [ anode in street ] [ anode in pavement ] [ street anode ] and others, none of which seemed useful) I switched strategies to a connected term -- to wit, "cathodic protection."

The query:

[ cathodic protection

took me to the Wikipedia article on Cathodic Protection, which nicely summarizes the situation.  A "cathode" is the other part of the structure to be protected from corrosion.  The anode is "sacrificial" in that it gets consumed in the process.  So... what needs protecting underground?

Reading farther down in the Wikipedia article answers the question--"Pipelines are routinely protected by a coating supplemented with cathodic protection."  Which are " anode, or array of anodes buried in the ground...and can be installed in a vertical hole and backfilled with conductive coke (a material that improves the performance and life of the anodes)"

Now we're getting somewhere!

We just have to confirm that this picture is actually of a sacrificial anode used in a cathodic protection system to maintain underground pipes.

The only other thing we know from the picture is that word "Christy."  Sounds like a manufacturer.  So I do the search:

anode cathodic protection christy

The first result takes me to the website of the Far West Corrosion Company with a page all about the Christy labeled Traffic Valve Box, 8-1/2" I.D. x 12... with a diagram that exactly matches my picture.  It's the right size, it's got the Christy brand mark, and it's labeled with "ANODE."

Found it.  By doing a little reading of web pages about "Cathodic protection anodes" on the Far West website, I learned a great deal about why you need cathodic protection for any metal pipes that are buried soil that's even slightly salty (which is nearly everywhere).

Moral of the story:  Sometimes a search term is just too generic to be useful.  In this case, "anode" is a great term, but it's hard to figure out the solution to this puzzle without learning that the key concept is "cathodic protection."  Once you know that, the rest of the search process is pretty straightforward.

When searching for a difficult term, consider looking around to find another term (not quite a synonym) that will get you to what you're seeking.

Searching, ever more sophisticatedly, onward!


  1. Dear Dan!
    You wrote: «Crazy: 90 Percent of People Don't Know How to Use CTRL+F»

    Deal is that search dialog in Chrome closes unintentionally, without user intervention.

    So «90 Percent of People» just don't want this mess on the keyboard to try call it again and again.

    If user call it with «CTRL+F» it must be visible (with browser restart, with surfing to other pages etc etc etc) until user close it with mouse click.

    Just fix.

  2. I believe is the far end of a lighting protection device. The metallic bar in the roof "attract" the lighting bolt, the electrical charge, that is conducted to the ground through a metallic cable. The connection between the cable and the ground is called anode, sometimes it demands a preparation of the ground around it and different types of metal to help the electric charge disperse and prevent damage to the building or any effect in the surface.

  3. A little Submarine Sacrificial Anode story.
    I just saw this old post. When I was in the Navy on submarines one of my jobs while we were in dry dock or repair was replacing the zinc sacrificial anodes in systems and on the hull. They get used up (they corrode instead of the ship) and must be replaced every so often. One of the problems we had is that the shipyard would carefully paint over the zincs with thick hull paint and thus making them useless. We would have to go chip off the paint from the zincs. Fun times hanging over the side of a submarine in dry dock with a chipping hammer 50 feet off the floor of the dock. Cussing the painters the entire time, but that is what sailors do, chip paint and complain, even on a nuclear submarine.