It generally goes without saying that we have a lot of metal artifacts to treat here at the Monitor Center. The term ‘ironclad’ does not exactly lend itself to images of wood or rope, but our collection of organic objects is not insubstantial. Thursdays have been devoted to survey of the organic objects in the walk-in refrigerator for the last couple of months, with a few breaks for other activities. This week we were doing something a little different, but still organic related. Some of you may recall that awhile ago one of the gun carriages was dissembled. The wooden sides still need to have their long iron bolts removed, an activity we hope to undertake soon, but for now those beautiful oak pieces are living in tanks with water, a corrosion inhibitor, and a biocide. The corrosion inhibitor helps to keep the iron bolts from corroding away until we can remove them, and the biocide prevents new ecosystems from growing in the lab. In addition to the corrosion inhibitor we are also using galvanic protection to prevent the iron bolts from corroding. The bolts are hooked up to magnesium blocks with electrical wire. Magnesium is less “noble” than iron in a galvanic series, which means that when it is connected to iron, magnesium will corrode faster than if it were unconnected. The other side of this is that the iron will corrode more slowly than if it were unconnected. So the magnesium will corrode into nothingness and the iron stays reasonably intact. The catch is that you periodically have to put in new magnesium blocks, an item we sometimes have difficultly tracking down. If anyone out there knows of a good source for magnesium blocks, please leave a comment or drop us an email.
So, as some of you may have gathered, Thursday was spent changing the solutions in these tanks and wiring in new magnesium blocks. Be sure to check back to the blog soon as we are testing dry ice blasting as a cleaning method this week. Hopefully there will be excellent results to share around this time next week.