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Wheat starch vs. sponge blasting

May 20, 2011

We are looking at 2 current options for removal of paint and other soft coatings such as silicone and polysulfide sealants from largish (2-3 square meters) areas of relatively soft materials or easily damaged materials such as aluminium or carbon/glass fibre.

Current advice is to use either wheat starch or sponge media blasting. I've heard very different opinions on both processes and would just like to use the experience from the people on here if possible.
Ideally I'm looking if anyone has any practical experience of either process. Particularly in terms of times and media consumption.

If anyone has any other ideas I'm also willing to listen to those however due to the product being worked we cannot use many chemical processes or chemical/slovent based paint strippers.

Ciaron Murphy
Process Engineer - South Wales, UK

Never heard of sponge blasting. Wheat starch might work; however, I'd look into a cryogenic system.

AF Kenton
retired business owner - Hatboro, Pennsylvania
May 24, 2011

I have heard that walnut shell media ⇦ this on eBay or Amazon [affil links] or pecan shells were used for that exact purpose. Media size/ distance /air pressure can be adjusted as required.

James Watts
- Navarre, Florida
May 24, 2011

May 25, 2011

Hi Ciaron,

My experiences with the removal of paints, varnishes and sealants from aluminium or other light metals (including magnesium) are such that I have always used chemical means to remove them. Any of the standard Aerospace paint strippers based on methylene chloride will do the job on the paints for you, you may need a very light blast with something like walnut shell to remove residuals. For the removal of sealants I have tended to use a Chemetall product called Ardrox 6345, very good on even fully cured polysulfide sealants, not so good on the silicones, but with persistence will work. For fresh sealant you could consider using Elixair Skywipes (make sure it is the non-lanolin version).

Carbon/glass composites are a very different animal as you well know, the solvent option really isn't there for that. Here it has been good 'ole mechanical removal for sealants (with scrapers and a steady hand!) and blasting with walnut shell for paints. Labour intensive and long winded. I'm sure others will have better ideas, but that is always the way I have done it.

Brian Terry
Aerospace - Yeovil, Somerset, UK

May 26, 2011

Thanks for the suggestions and effort put in.

I'll add the following link to sponge medias for anyone who has an interest.

www.spongejet.com/

Caron Murphy
Aerospace - South Wales, United Kingdom

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