Grit Blasting

[Seano]

This is an issue that has been raised at work, we quite often need to fab double footplates for some clients wheelchairs, now these are cast aluminum and are painted, they also have rubber matting stuck to the foot pad.

Now we remove all the glue left after removing the rubber using 'MEK' then a few people tend to grit blast theirs before butt welding, my argument is that the blasting media we use cold iron grit (because we also need to remove powder coat also) my thinking is that because of the pressure used there has got to be some iron contamination left behind in the aluminum casting after blasting, a more learned view would be appreciated to put this matter to bed once and for all....

 

[Paul.]

Chilled iron grit will contaminate the surface, leave a grit blasted component out in the rain for a few hours and see what happens to it, I specify glass bead for any aluminium or stainless work, it gives a much finer finish with no contamination, there are probably other media just as suitable, but not iron based

 

[Seano]

Ahhhhhhhhhhhh, the voice of sensibility, I'm glad to see someone else knows what they are talking about....

 

[troppo]

I would advise using someone that knows how to use the media properly too.
We had truck come in with warranty paint faults, the boss got the cheapest blaster he could find to come in and Soda blast the body to strip it (the body was constructed fron an aluminium extrusion), after blasting we vinegar wiped the body as you should but paint just wont stick. One of our paint reps came in and knew straight away what was wrong (old school paint guy) the blaster didnt know how to use soda and had the pressure way too high, turned out he was using about 2.5 times the right pressure and so had embedded soda in the aluminium to the point where it would almost need to be soaked to make it paintable. Blasting media all have their own specialty needs

 

[brightspark]

if your wanting re usable media try using guyson turbonox stainless steel bead they do it in 5 diffrent grades .for use on non ferrous metals and doesnt leave any surface corosion other than that use aluminium oxide if its getting coated . if not finish off with glass beads

 

[guiness]

when i blast alloys
i use cold iron grit then place wheels into dish washer to remove any grit behind