What is one of the Museum’s constant companions with its collection of old parts? Corrosion! It is obvious that in collecting/storing/restoring/displaying artifacts of significance to the Museum there will be many objects that are not in their original pristine condition. So what are some of the trade secrets when the Museum receives a donation that has lain on a hillside, or in a barn or backyard for many a day? First, there is the general cleanup of exterior deposits of dirt, droppings and debris. Once down to the bare metal the item is examined to identify the material and determine the appropriate cleanup process.

Light aluminum alloys, typical of aircraft structures, are fragile and need to be cleaned up with care. Strong corrosive substances such as paint strippers are to be avoided. Techniques, such as blasting with glass beads, is usually sufficient to remove paint and light corrosion.

For heavy-duty steel structures (rare on aircraft) a course of sand blasting may be the right thing to do. For lightweight aircraft structure this would do far more damage than good. An alternate process for ferrous metals (iron-based materials) is an interesting technique borrowed from the car restoration community. This is a molasses-bath process that removes the rust without damaging the underlying structure. As it is an immersion process, all interior parts of the metal are exposed to the cleaning action, not just the visible exterior as with some cleaning methods.

Molasses for cleaning? A molasses mixture of about 10:1 water-molasses is used. The water and molasses mixture when left exposed to air ferments and produces, amongst other things, Acetic Acid. This reacts with the oxygen in the rust and when the iron oxide (rust) is all reduced, the process stops. The steel or iron is not affected, but the surface of the metal is now virtually in original condition and subject to immediate attack by oxygen in the air and will begin to rust, so must be protected. The benefit of using molasses is that it dissolves that rock-hard rust that even wire brushes can’t touch and carborundum cloth can’t reach.