11" Dahlgren

[Garret]

There's an 11" Dahlgren on Ebay that the seller claims was put in electrolysis for five years yet still lost surface iron.  Does this happen very often?  

http://www.ebay.com/itm/Civil-War-11-inch-Dalgren-Artillery-Shell-Shot-Cannonball-Bolt-Ball-No-Reserve-/190608260119?pt=LH_DefaultDomain_0&hash=item2c61233c17#ht_668wt_1189

[Dave the plumber]

 Garret,       It looks like this shell was initially recovered from salt water and was left to dry out before being run. You need to keep a salt water recovered shell soaking in water until the point you start electrolisis, otherwise it will eventually look like this. I'm sure Pete can give us an official explanation of what occurs ..........
     Also, I never have heard of a shell being run for 5 years. Unless the thing kept ' calving ' through the years. Typically a salt water shell takes about 2 years of low amperage to stabilize it and remove the salts. There is an art to the process that I have not personally tried, and there are a very few guys out there that know what they are doing and can save a relic correctly. Obviously this shell was not handled properly some where down the line.
                             David

[pipedreamer65]

2-3 years max for a salt shell in my opinion.  Larger items like cannon and such may run for years and years.

Well, as far as the condition of the projectile, the law of averages applies.  Some times they just don't turn out well, no matter what you do.  The Dahlgren appears to be a marsh shell to me.  Many times, items that come out of brackish water and mud will lose their skin and chunks of iron that were not good quality iron to begin with.  On the bright side, the relic appears to be pretty stable.  I doubt it will give anyone trouble down the road.  A decent shell for a collector on a small budget.

[alwion]

opps you got here before I got logged in. I've read and read since I got the 4 7" shells from this same fella, and then found my 10" columbiad with some problems( see other post). Talked on the phone to some knowledgable people also. I was VERY concerned about the 4 salt shells I have, and hear what I felt I learned, you others can correct me if i'm wrong
1. shell should be kept in water till electrolisis
2.three plus years isn't always done but not uncommon, but probably can't hurt
3.damage to a projectile is often under the surface of a shell, even before its found. Somewhere I saw
   a cut of a shell showing the damage underneath of a otherwise great looking shell
4. because of the last idea, salt shells are a risk because the disintegration can show up so many years later( see all the sad stories under distressed "10 inch columbiad) even if everything is done properly doesn't , you still may loose the shell down the road. You can't fool mother nature, she had it before you did.
5. coating make little difference, except for the surface rust. If its still rusting inside, it's still going to fall apart

[Pete George]

Dave the Plumber wrote:
> I'm sure Pete can give us an official explanation of what occurs.

  I hope the following explanation will serve to answer Dave's question and Alwion's several questions.

  The problem has to do with the "porosity" of cast-iron.  Unlike other most other metals, cast-iron is extremely porous.  It contains many thousands of micro-bubbles.  Under a microscope, the interior of cast-iron looks (literally) like Swiss Cheese.  Those thousands of micro-bubles allow salt water to intrude deep into the iron, if the iron is exposed to saltwater for a significant number of years.

  When that saltwater-environment iron relic is removed from its burial place, its internal micropores have a lot of saltwater in them.  If the relic is allowed to dry out for several weeks, the internal saltwater begins to evaporate.  As the water evaporates, the dissolved salt in it will transform back into its solid crystal form.  The crystal's growth is physically powerful enough to crack the iron ...much like stone can be cracked by water as it freezes into water-crystals.

  Coating the iron with various substances slows down the water-evaporation, but cannot permanently prevent it, because (apparently) no coating is absolutely 100% air-proof.  Apparently, even the coatings have micro-pores, which permits evaporation to occur, although at a much slower pace than it will without a coating.  Some types of coating are more effective than others.  Paint and lacquer are quite porous.  Insofar as I'm aware, Polyurethane provides the best long-term protection against air-intrusion.

About "the law of averages" mentioned by Pipedreamer:
  I believe the problem is based on how much time the iron was directly exposed to the saltwater.  If an artillery shell strikes forcefully into the saltmarsh (or river-bed) soil, going deep into the soil, it can be fairly effectively protected from the saltwater.

  For example, I've personally examined several Harding shells which impacted directly into a deep thick clay deposit under the ocean's surface off of Charleston SC.  (Note, that peculiar grey clay is not sand, nor silt, but instead has the thick consistency of the infamous North Georgia red clay.)  Apparenty, the clay is so non-porous that it protects the shell's iron body from saltwater intrusion.  The Harding shells which were dug from that under-ocean clay deposit were cleaned only with short term "regular" Electrolysis, and they've held up just fine for over 20 years.

  The 12-pounder Whitworth Bolts recovered from the legendary Modern Greece shipwreck are another example.  Insofar as I'm aware, because they were recovered back in the 1960s and early-1970s, none of those Whitworth Bolts got Electrolysis treatment.  The result was that some of them fell almost entirely to pieces ...and some scaled "significantly" ...and some scaled only a little bit.  The apparent answer to that mystifying conundrum is the same as the previous paragraph -- namely, how much time they were "directly" exposed to the saltwater.  Apparently, some of the Modern Greece Whitworths were not deeply buried in the silted-over shipwreck, and others were very deep in it.

In summary:
  It seems a lot depends on the soil conditions that the iron was buried in.  Some received extensive exposure to saltwater, and some, much less.  Once the relic leaves the hands of its original finder, there is no way for us to be sure about what those soil-conditions were.  So, I think its best to treat freshly-recovered ones as if they ALL require keeping continuously wet, and long-term Electrolysis, and coating with Polyurethane afterward.

Regards,
Pete

[Dave the plumber]

   Pete,   
     thank you very much for your great reply. We all learn so much from you......thank you.

          When purchasing a former salt water shell, or finding one and running it yourself, there is no doubt you are rolling the dice and taking your chances. Even if the most experienced electrolisis runner in the U.S. runs it, there are factors that could come into play.
       Firstly, is the quality of the iron used. And this is especially true when it comes to CS manufactured shells. CS shells had less quality control on the iron than US manufactured shells.
       Secondly, as Pete pointed out, is the enviroment the shell has rested for 100 plus years.
      Thirdly, is how the shell has been kept since being recovered.
      Then comes in factors of amperage used, electrolic medium, anode material and positioning, frequency of water changed and a whole lot more I am sure I am not aware of. That is why I pay someone versed in the process to do my shells. It's too expensive  a learning curve to loose a good shell. And too important for the relics sake to learn as you go.                David