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Posted by Wayne on August 17, 2001 at 09:02:00:

In Reply to: Re: Using "a degreaser like 409 or Simple Green" posted by Jeff B on August 16, 2001 at 20:53:33:

This is strictly non-diving-realated, but here goes.

In VP-PAW and VP-GTAW type of welding of aluminum for spacecraft fuel and oxidizer tanks, we worry about porosity int he welds. The porosity comes from hydrogen being forced out of solution at solidification from a 20 fold decrease in soluability at the temerature where solidification takes place. To prevent these bubbles we try hard to exclude oils because the high temp plasma will break down the oils and the hydrogen is absorbed into the liquid aluminum.

We ran a bunch of cleaning experiments to see what did the best job of removing all troublesome stuff. We did everythign imaginable from solvents, soaps, detergents, scraping, wire brushing, staring at it really hard, etc. We found that nothing available back then did a better job than Simple Green. But there were problems there also. Mostly it had to do with adequate rinsing. We used HOT D.I. water to get good results.

Do we make flight hardware with Simple Green? No. At the present tiem I am a total fan of the stuff from Today & Beyond in Ashland Ohio. Works better than everything else we have tried and does not cause selective corrosion problems, and it does not etch the surface. I have used their stuff on aluminum, titanium, nickel-based superalloys, and a few steels. Amazing cleaners.

Hope that clear it up a bit. The couopons done with S.G. were used for fatigue samples and never flown.


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