Can someone tell me whats this is from?
 

What is this from, and how do i prevent it? I sandblasted my cab, cleaned it, and epoxyied the cab. The cab sits in the garage. I did some metal work after that, and about 3/4 months later i notice this.
http://img.photobucket.com/albums/v6...d/DSC00364.jpg

That area is the left kickpanel. Thats where the floor meets the kickpanel. Only thing i can think is that its metal shavings that have rusted... I obviously cant paint over that right???

How do i prevent this? I thought epoxy didnt rust... There was NO moisture at all except for regular air moisture in a garage...

Re: Can someone tell me whats this is from?
 

Well if you did any grinding the flakes can embed in paint or even glass and start to rust....also are you sure you coated the corners well enough

Re: Can someone tell me whats this is from?
 

My guess would be it sat too long after sandblasting before it got primer on it or if you primed it right away maybe you didnt get that area covered good with primer and humidity set in to cause the rust on the raw metal.

Re: Can someone tell me whats this is from?
 

how did you clean the cab after blasting?

Re: Can someone tell me whats this is from?
 

Is that old sealant or new?

Re: Can someone tell me whats this is from?
 

If your metalwork involved grinding, the grinding disc heats up the metal fragments which become hot, flying particles. The hot particles then come in contact with the epoxy primer and some are hot enough to melt their way through the primer and come in contact with the metal base. Some are just loose metal particles that rust.
If it were me, I would just scuff it and shoot it when ready. As long as you don't leave it exposed to the elements, it will be ok till you do so.
Always take the time to blow off surfaces once you grind anywhere around them.

Re: Can someone tell me whats this is from?
 

***Ram-Man Re: My guess would be it sat too long after sandblasting before it got primer on it or if you primed it right away maybe you didnt get that area covered good with primer and humidity set in to cause the rust on the raw metal. ***

It did sit for quite a while inside the garage. THere wasnt any rust really but there was some light browning in that area. I just cleaned that up and coated over it.... It was only in one section of the cab. Is that where i messed up???

I was sure i had at least a thin coat on it. Its always in the garage.

wax.grease remover, air. Just whateve rit took to get rid of the dirt.

Its new epoxy. DP

So overall consensus is, grind, or wire wheel the affected area and then recoat?

Re: Can someone tell me whats this is from?
 

Thats fairly common in a crowded shop. Like stated above. We had a client refuse delivery on a S/Stl heat exchanger cause they said it was rusting and would not let it be unloaded. All it was grinding residue that rusted off another piece of equipment made from carbon steel that was close by before it was shipped. it was easy to take off but they should not have shipped it that way. Thats what it looks like to me from the pics.

Re: Can someone tell me whats this is from?
 

i find that when blasting with sand it is necessary to clean and scuff with something like rolac wheels or at the very least a scotchbrite pad to remove imbedded blasting media particles from the metal// wiping down with solvent soaked rags is not enough

Re: Can someone tell me whats this is from?
 

Ya, i didnt roloc it down.. I just cleaned it. ALSO, there was some browning in that section.

Im just going to wire wheel it down, grind it, clean it with some acid, rinse it off, then reepoxy over that particular area... Any other suggestions?

Re: Can someone tell me whats this is from?
 

I was referring to the seam sealer. My bad. You need to remove the seam sealer, get behind it, coat it good, and put new seam sealer there.

Re: Can someone tell me whats this is from?
 

Ya, thats old sealant in that area...

Im going to redo that area, no biggie.. I need to spray the cab, so i will just redo those sections and respray it...