outgassing

[irelandmoss]

I read where people talk about outgassing.

I am new to this and it may sound like
a stupid question, but what is outgassing?

Thanks for any help.
Bill

[uricad]

If you go to my site: www.powderplus.biz, there is a picture of an part that has outgassed. go to photos>bad examples. It was done intentionally to show what happens. Basically the air in the cavities tries to escape during cure, which creates little bubbles in the flowing powder. It's a pain to deal with, so I don't even mess with most porous parts, unless it's for someone I know.

[Harleydad]

As uricad said the pores of cast materials release air and contaminates trapped during the casting process. Out gassing the part before applying powder helps to combat this. Out gassing is basically heating up the part to release this stuff. I usually out gas at about 50 degrees above the cure temp of the powder for about an hour.
1. clean and degease
2. media blast
3. outgas
4 clean and degease again
5 powder and cure
Some like to blast after out gassing.

There are a couple other things to help combat this. Out gassing additives that mix in the powder or an out gas forgiving powder (colors are limited here).

[PCT17522]

I agree with Harleydad's process. I would warn against blasting after outgassing, but it's only a theory: If you blast after outgassing, you may open new pores in the metal that haven't been outgassed. I have also run across situations where this process doesn't work 100%, but have not yet been able to explain why or what will work, although I've never tried the OGF additive.

[baz]

if i need to outgas i also go by harleydads process . i do not see the need to blast again . it would be a waste of time since the part has been cleaned after outgasing.

[HardShell]

I recently did some poor quality aluminum castings that had to be outgassed +70 degrees for two hours, anything less and they'd bubble. I also added OGF additive for safe measure cuz I was sick of stripping them.

[FiReBReTHa]

Originally Posted by HardShell

I recently did some poor quality aluminum castings that had to be outgassed +70 degrees for two hours, anything less and they'd bubble. I also added OGF additive for safe measure cuz I was sick of stripping them.

curious how you stripped them.

I had some issue recently and now need to redo for the first time.