Outgassing? How long

[estevahn]

What up guys

I was just wondering when you outgas an aluminum truck rim for example, when you take it out of the oven is there a time limit on how long the part can sit out before you coat it?

Will the aluminum take in gases again?

Any info about this will be helpful. Thanks again, Jeff

[pdeinc]

The 'gases' that you drive out during pre-heating are typically volatile components of various contaminants like oils. I think it is also important to clean the surfaces after a preheating, especially parts like valve covers that have been in contact with oil for some time. The pre-heating drives these vapors out of the casting pores where they can condense on the surfaces.

In theory, as the part cools, no more contaminants are introduced into the metal as long as the expelled ones are cleaned away. You do have to be careful about cleaning a hot part as the cleaning solution will tend to dry on the surface and leave a film. Use a very mild soap solution followed by a thorough rinsing with clean water.

For some used castings that have been in contact with oils and such, it may pay to allow the part to cool before cleaning the surfaces, and then repeat the pre-heating before coating.

i will out gas and then shoot the part with in 10 minutes the part will still be around 125f and it will allow the powder to seal up little crakcs and pores
good luck