Issue with milscale will spi epoxy stick?

cllong1

Active Member
So far everything was going perfect stripping paint down to metal. Today I was stripping my hood and realize it was a problem once I started sanding. The Hood was covered with all this crude that is the right side. So, I sanded one side so you could see a comparison. I went through about 12 80# discs and still couldnt remove all the mil scale. I noticed that every time i put new sand disc it would get a little cleaner. My question is is this mil scale and have I removed enough for the epoxy to stick or do I need to keep sanding? I can tell you that I cannot get it clean bare metal like other parts of the car, so just any suggestions to prep the hood for epoxy. I added some pics for you to see what I'm talking about. It just doesnt seems like at least 50 percent of this stuff off. Please advice..... Thanks
 

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texasking

Active Member
Short of blasting it (which is very risky on a hood), that hood is a perfect candidate to try some Ospho. It may take more than one application, and lots of scrubbing with a red scotchbrite, but it should work. Just read on here (or call Barry) about the neutralization process after Ospho before epoxy.
 

Chris_Hamilton

Trying to be the best me, I can be
You can get it at farm supply stores as well it's called milkstone remover. Places like Home Depot and Lowes sell Klean Strip brand. Think they call it concrete etcher. What you are looking for is Phosphoric Acid. I've gotten the Ospho brand at Ace Hardware in the past.
 

cllong1

Active Member

Chris_Hamilton

Trying to be the best me, I can be
Get a decent empty spray bottle. Liberally apply the product. Allow it to sit for awhile, then you can apply some more and use a red scotchbrite pad to scrub and help remove any rust. When you are ready to neutralize it, simply re-wet the surface with Ospho let it sit a few minutes. Keep the panel wet with the product. If you see any black cruddy buildup you can use the scotchbrite to help remove it. Keep it wet don't let it dry and while it's wet rinse well with water. From the tap is fine. You may see some staining and orange tint. That is OK. Something llike that hood after I rinsed it and it dried, I would go back over it quickly with 80 grit on the DA. If you do sand it, blow it off, wipe down with 700, then epoxy.
Main thing to remember is that you re-wet the panel (if the acid dried) then rinse.
 

texasking

Active Member
That's the one I use. I put it in a spray bottle. Use a mask, gloves, and eye protection! Spray it on nice and wet, work it in with a red scotchbrite keeping it wet. If there are deeper pits, you can use a wire brush or a little blasting media with the scothbrite to help get in the pits. I usually wipe the excess off with a dry rag just to make it smoother, but it is not crucial. Just let it dry overnight to do it's thing, and repeat. The metal should look a lot cleaner when you respray it. Neutralize it as the fast-typing Chris says above:)
 

cllong1

Active Member
Texasking asked me to do a search on the forum and I found barry's guide to "How to neutralize Ospho" dated May 15 2015. Here he lays it word for word, and I had seen Fireman's Ospho torture video but it never made sense until after I read this and you guys explained to me very well. So I'll be back when the Ospho comes in.
 
Texasking asked me to do a search on the forum and I found barry's guide to "How to neutralize Ospho" dated May 15 2015. Here he lays it word for word, and I had seen Fireman's Ospho torture video but it never made sense until after I read this and you guys explained to me very well. So I'll be back when the Ospho comes in.
Neutralizing is just common sense. The more you apply, the more white powder ends up on the parts you treated. You rinse it off, and the powder haze keeps returning. You just keep rinsing until all the haze is gone. If the ospho does not haze anymore, it has been neutralized.
If you just use wet rags you really can see the surface getting the rainbow blue haze or an iron phosphate instead of dousing it with water. It takes a little longer, but at least you are not dumping water into surfaces that might not have been treated.
Wear a respirator if you have problems with fumes.
 
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