Dry Ice Blasting: Yorktown Guns Addition

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This week we’re taking a detour from your usual Turret updates for some Dry Ice Blasting! After quite a bit of research we figured out the best settings for Dry Ice Blasting on cast iron (previously we’ve only treated wrought iron with this method) and our first application is for the treatment of a pair of British guns from The Revolutionary War.  These guns were part of the armament on transport vessels supporting General Lord Cornwallis’s British army during the Yorktown Campaign. The guns were sunk when Cornwallis ordered the transport vessels to be sunk as obstructions, to prevent the nearby French fleet from coming to the aid of General George Washington’s troops.

York Town Gun before Dry Ice Blasting
York Town Gun before Dry Ice Blasting

The guns were raised from the York River in 1934 through a joint effort by The Mariners’ Museum, National Park Service, and Newport News Shipyard, and they’ve lived happily on and off display at both Yorktown and The Mariners’ Museum. But as you can see, they need a little TLC before they can be displayed again.

When they were last treated, a protective coating of paint was applied to the guns, which worked for a number of years to prevent corrosion, but has recently started to peel off of the surface and corrosion has formed where the paint failed. The old paint now has to be removed because it can trap salts within the iron. I’m sure many of you remember from previous posts that salts are the bane of any object (and conservator’s) existence, and will cause metals to corrode.  Removing the paint will allow the salts to flow freely out of the guns during desalination.

We applied a solvent to the paint to soften it, and then used Dry Ice Blasting to quickly remove it.

Laurie Dry Ice Blasting
Laurie Dry Ice Blasting

The blasting treatment was so much fun and worked even better than I’d imagined.  In only a matter of hours I was able to remove the paint and active corrosion from the surface. You can really see the difference!

A comparison of before and after the Dry Ice Blasting
A comparison of before and after the Dry Ice Blasting

Now that I’ve had all my fun Dry Ice Blasting this week, the guns are ready for Electrolytic Reduction and Desalination.  You may see them again in a month or two for another round of Dry Ice Blasting, so stay tuned!

All done!
All done!

7 thoughts on “Dry Ice Blasting: Yorktown Guns Addition”

    1. Haha good point! I put a small camera down the barrel of both cannons to see the corrosion on the inside–and I saw that fortunately they are not loaded! What a relief for me.
      Thank you for your interest and support!

  1. Hi: I came upon your site somewhat by accident but I may have useful information. I worked with metals around salt water here in SF Bay and found that sometimes blasting with particulate of any form sometimes ‘peens’ salt (or chloride) laden cavities (microscopic to be sure) closed, only to have these cavities erupt later to undo our work. We achieved best, longest lasting coating application by preparation with very high pressure water (45,000psi) blasting using de-min water so as not to introduce any chlorides into the surface, then using a solution of “Chlor-Rid” to wash the surface. This is a commercially available product that chemically joins and flushes out those salts still remaining after the water blasting. This product was approved by our environmental groups here for use above the SF Bay water. Coating commences immediately the surface is dry of course as oxide bloom starts immediately in normal atmosphere. Well, this is what is working for us here on the west coast, good luck in your good works!
    Regards
    Tom Alex.

    1. Hi Tom, thanks for you input.
      We’ve tried a number of concretion, corrosion and chloride removal methods in the past at the Mariners’ Museum, and the dry ice blasting method is proving to work very well for us. Not only does dry ice blasting remove significant corrosion which can trap chlorides in the object, but it does not damage the surface of the object, even on a microscopic level. Also, these cannons are currently going through desalination, a long-term process to remove chlorides. Over the next few months I will be monitoring the number of chlorides being removed from the cannons, and once consistently low readings are achieved, then the object will be dried and coated.
      Thank you so much for your interest and good luck with your work in SF!

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