Dear Mr. Dorris,
They used the dry ice stripping method experimentally for depainting aircraft. Boeing will R & D new, potentially viable stripping methods. They are obviously interested in maintaining the life cycle of their aircraft and giving their customers the best methods for maintaining the aircraft in use. They also want to reduce, as much as humanly possible, the liability for potential problems might arise from any maintenance procedure (i.e.-depainting, NDT, refurb, etc.).
They have in the past issued approvals for dry stripping using Plastic Media Blasting. An aircraft could be stripped once using Type II. Later, they issued another approval for five strip cycles using Type V. Currently their main stripping media focus is on using Wheat Starch. Because of the increasing use of composite materials in the aircraft industry, they are continuously searching for the best "mouse trap."
Wheat Starch is a low aggression material which has shown excellent results for stripping soft aluminum and composites. The reason I can speak of this knowledgeably is because we are currently working with their military and commercial facilities in WA and KS on this program. We are one of only two manufacturers of wheat starch abrasives in the world.
Boeing, being a very conservative company, will test to death various maintenance methods before they will sign off on one. They, as stated earlier, want to reduce their liability to zero for any operations which could effect the performance of their aircraft. That is probably one reason the 707 mentioned in your inquiry is for museum display.
My knowledge of dry ice media is not limited to the aerospace industry. It is also used in the rubber and plastics molding industry for mold cleaning. What I know of this from customers comments and being around the operation is that the process is loud, expensive and cumbersome. Not only will you have to buy equipment to run the process for making the dry ice pellets, but you have to buy dry ice and will probably have to invest in some sort of chiller using Liquid Nitrogen to keep the dry ice from dissipating(Liquid Nitrogen - LN2 - is not cheap). I have seen a stagnant dry ice operation at Robins AF base. That is where I realized additional capital investment in the LN2 auxiliary equipment.
If you have any questions for me, I am available at 800 340 7523
Matt Callahan
MPC Industries, Inc./ Patent Plastics, Inc.
Knoxville, TN
