[Shop-talk] powder coating

[Mike Rambour]

  Cast Iron is really bad at out gassing and causing bubbles, pot metal 
less so but still will do it.

  most metals wont out gas and the real cause of bubbles in most metals 
is improper preparation, something like fish-eyes in paint where oil or 
a oily fingerprint was left on the surface.

  The fix is pretty easy for most items, you pre-heat to cure 
temperature and spray with a solvent to clean the pores, you then 
re-heat to cure temp to dry it all out and powder coat after it cools 
back down.  Not letting the part cool completely and coating it while 
still hot helps quite a bit but requires a bit more finesse to coat it.  
I have had to pre-heat/spray solvent some previously very dirty oily 
cast iron parts 2-3 times to fully stop out gassing, previously painted 
or never got really dirty cast iron just pre-heat one cycle and coat.

   Mike

On 2/11/2014 2:02 PM, Tim wrote:
> Any one ever heard of "gas out" and it causing the powder to bubble or
> pit? I have to assume that the pitting was caused by the sand blaster
> but since this is the first time I have ever had something powder
> coated, I really have no clue.
>
> Thanks
> tim
> _______________________________________________