There is a risk in blasting any mechanical component, my friend has a blasting business and has guys bringing in motorbike engines and gearboxes regularly. The owners try methods of keeping the media out but nothing works, it gets in, the seals fitted are to stop internal fluids coming out not external fluids under pressure getting in, my mate makes them sign a disclaimer and often talks them out of doing it.
Soda blasting is the least abrasive and in theory it leaves no residual media as it vaporises on contact, you will still have to degrease it first or the media will simply bounce off grease or be absorbed.
In the past for cleaning alloy components I have used a product called ALTRANS, its made by DEB, its an acid solution and smaller items can be soaked in it or larger items can be cleaned in a similar manner to using Gunk. It tends to clean to a dull natural finish, if you wants a white/silver finish only blasting will achieve this.
Alternatively get it steam cleaned at high temperature and paint it with an aluminium paint, sometimes a painted finish is better because a raw casting that's been blasted absorbs dirt and grease and is hard to clean.
Ultimately the best finish is to strip the part down, blast it to a raw finish and then seal it with a clear satin lacquer, that is how I have done my own concours projects in the past.
Cheers, Paul
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