Media Blasting, how clean is clean?

7

72gs455

I set up a media blasting booth (old fishhouse) in my garage to get into all the nooks and crannies. I need to know haw far I need to go with the blaster. I am down to bare metal, some areas are discolored from surface rust, you cant feel any difference in clean areas and dark areas. I dont want to go though all this work if the rust is going to pop back up. I am epoxy primering with SPI , before doing any body work.
I posted this on another site to get their reaction as well.
Thanks,
Jerry
 
The other site will prolly tell you to coat it with POR 15 ROLOL.

Shine will have the correct answer.
 
Obviously, the perfect situation is to have no corrosion left on metal that is to be primered. Discoloration indicates corrosion is still present. I would suggest that leaving slight amounts of corrosion might be acceptable for a floor pan or maybe even a door jamb, but on the exterior of the vehicle, where lots of time will be spent ensuring a flawless finish, it may not be a worthwhile gamble to leave something that can cause a hard to repair problem later.

The short answer is it needs to come off.
 
This is my opinion:
The stained metal is rusted metal that needs to be blasted clean.
If it is too thin when done then it will need to be cut out and a patch welded in.
Yes, there are short cuts and "treatments" but if you want to do it right . . . the rust has got to go.

The more knowledgeable are welcome to correct me as always.
 
the discolored surface will be no problem once sealed with epoxy . depending on the media your using you may not be able to get it all. after i wash a car i get a coat of flash rust on it. i just scuff it down and epoxy it. once over with 80 grit should get you clean . surface rust takes years to do any damage setting outside. it is the areas covered by dirt , carpet or por15 that will eat through the metal. anything more than slight surface rust has to come off. you can not cover scale with anything. that is creating a rust hotel .
 
Here is a discolored section:
P1010011-1.jpg


Spent just a few more minutes blasting, then DA with 80 followed by 180:
P1010010-1.jpg
 
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