Help with epoxy question

[slammed57]

Hey all, questions about prepping metal before epoxy. I stripped all the paint off using a strip discs. I have these black areas that look to be in the metal it’s self. I tried a small area with a 50 grit grinder disc to see if I can get to white metal, but it still remains dark or black. If I was to have it media blasted It May look all uniform. So my question if I was to epoxy over this would I have any issues down the road. Or should I have it blasted. The shop down here uses black diamond for its abrasive. or how about using ospho? Your thoughts?

 

[Slofut]

Strip disks tend to soften and smear material on the surface. I would try a da with 80 grit first and see if it changes. (I realize you used a grinder with 50g) Pretty sure you'll see a difference.

 

[slammed57]

Well I tried the 80 grit with the DA and not really much better. I did the other fender today same exact method and it came out beautiful. Iam just trying to understand what’s going on with that other fender

 

[slammed57]

the best I can explain it, is that it resembles mill scale.

 

[texasking]

That fender looks a lot like some of the roofs on these older trucks. Most of the time it is from the paint being very thin or gone and the metal has no protection. Maybe the other fender had been painted at some time and it saved the metal. Blasting is the best option, IMO.

 

[Slofut]

Yea, that's more than just paint residue. I agree with tex, if the da didn't make any difference I wouldn't be happy until it's blasted.

 

[jlcustomz]

If you don't have blaster access, could try a few spots with stiff wirewheel in grinder, then re- da with good sharp paper. May not always look uniform, but at least needs to be clean.

 

[Chris_Hamilton]

Hey all, questions about prepping metal before epoxy. I stripped all the paint off using a strip discs. I have these black areas that look to be in the metal it’s self. I tried a small area with a 50 grit grinder disc to see if I can get to white metal, but it still remains dark or black. If I was to have it media blasted It May look all uniform. So my question if I was to epoxy over this would I have any issues down the road. Or should I have it blasted. The shop down here uses black diamond for its abrasive. or how about using ospho? Your thoughts?

If you can't blast, hard cookie disc on a die grinder/drill will get it off. Sometimes a wire wheel brush on the drill works ok as well. Ones I use are 3M 7460. Come in a bag of 10. Mount them on a mandrel in an air die grinder. They don't work as well in a drill. Extra speed of the die grinder helps. Doesn't hurt the longevity of them either.

 

[slammed57]

I’ll take it down and get it blasted with black diamond. I’ll report back, thanks everyone for your input, I appreciate it

 

[Slofut]

You'll have a great substrate for epoxy

 

[slammed57]

Came out great after blasting. Texas king was on the money, it had thin paint on it. I assume the oxidation gets baked in from the sun and absorbed into the metal. Thanks everyone for all the help. Going to hit it with 80grit DA sander clean it with 710 and get some epoxy on it

 

[texasking]

I've never figured out why it gets so hard to remove, but I know every thing in the tool box and Ospho wouldn't touch it. A knotted wire cup brush on an angle grinder and a 36#, 5" grinding disc just polished it. Blasting it off wasn't easy. That black factory primer gets incredibly hard when exposed to the elements, but there is rust under it, somehow. Looks great.