Q. Let me suggest another alternative to your suggestions for treating the piece of steel from the World Trade Center, described in the September issue. First, I agree with your cleaning procedure. After that, consider coating the relic with one of the three parylenes. The stuff might be only a few microns thick, but it resists attack by heat, chemicals and abrasion.
I first found out about parylenes in the 1970s working for a computer manufacturer that used parylenes as conformal coatings. The DoD, NASA, museums, and medical equipment and toy manufactures, among others, all use parylenes because of their superiority in performance when compared with both epoxies and polyurethanes. They are better in penetration and uniform coating thickness on all surfaces, including contorted passage walls under 0.01 microns; coverage around and behind corners; adhesion to various substances; and effectiveness starting at submicron thicknesses. They can be applied as thick as any paint with no occurrence of pin holes, no volatiles, high electrical breakdown strength, less moisture diffusion, less gas diffusion, high chemical resistance, UV resistance, optical clarity, abrasion resistance, bio compatibility and the ability to stabilize delicate objects.
There are perhaps hundreds of parylene coaters around the country, but since the process takes place in a vacuum chamber, one would need to find a contractor with a vacuum chamber large enough to accommodate the artifact to be coated. The vacuum requirements for the various parylenes polymerization/deposition processes are about 0.1 atmospheres, not much of a vacuum by today’s standards. While most of the parylene coaters can handle objects about the size of a briefcase, some can do objects larger than a refrigerator. C.S.
A. Thanks for the input. Parylene would be an excellent choice for coating the I-beam. The problem would be finding a coater able to handle it, as it is much larger and heavier than a refrigerator.