What's the best prep for epoxy pimer after parts have been sandblasted?

[pb4ugo]

As the title says. I'll be painting the dog house of my FJ40 soon. The fenders are new, and the hood will be sanded and they will be epoxy primed. I will be sandblasting the fender aprons and bib. Do I need to clean and prep these sandblasted items b4 spraying epoxy primer? If so what's the best approach and products? Thanks, Ken

 

[Krondor]

Wax and grease remover. Wipe on, and wipe off while still wet with a clean cloth. This will remove any last contaminates before you lay on the epoxy.

 

[RUSH55]

With lint-free cloth. As much as possible, try to move it in a single direction as not to redistribute contaminants. Fold your cloth as you work to continually give you fresh cleaning material to work with and add small amounts of wax/grease remover as needed. Go over each area until the cloth is no longer picking up contaminates - completely clean. Use rubber/latex gloves to keep from transferring oils from your fingers to the cloth.
Get comfortable and familiar with this step and do it between each stage of painting.

 

[Splangy]

Wax and grease remover. Wipe on, and wipe off while still wet with a clean cloth. This will remove any last contaminates before you lay on the epoxy.

no no no.

use the wax and grease remover before blasting (with clean grit) and then just blow the parts clean with clean air. Epoxy immediately.

blaring greasy parts just contaminates the metal and wiping after blasting leaves lint on the surface.

 

[Krondor]

That was verbatim directly from the paint specialists at finish masters. If you blow it off with air, you still have all sorts of contaminates left on by the sand blast. (Stuff you cant see) Good luck with your finish sticking properly without taking that off. By using the wax and grease remover and wiping while wet, it lifts off any remaining contaminates/oils from the sand along with any fingerprints accidentally left.

 

[RUSH55]

What about contaminates in the compressed air?

 

[Splangy]

That was verbatim directly from the paint specialists at finish masters. If you blow it off with air, you still have all sorts of contaminates left on by the sand blast. (Stuff you cant see) Good luck with your finish sticking properly without taking that off. By using the wax and grease remover and wiping while wet, it lifts off any remaining contaminates/oils from the sand along with any fingerprints accidentally left.

Lots of people have this backwards. It’s very common.

This is well documented throughout the protective coatings industry. I’m not making this stuff up. Review SSPC SP-1 and SSPC SP-5 standards.

Any solvents and whiping after blasting should only be done on an as-needed basis to address Specific local concerns. If you blasted with clean air and clean grit, there are no chemical residues left over which solvents would help remove. Clean, dry compressed air will remove blasting dust better than anything else.

furthermore, whiping a blasted surface with a rag will leave lint on the surface. You’ll struggle to remove all of it with compressed air. You likely won’t even realize how much is there until you spray your first coat of primer. Any lint remaining will act like a wick and will facilitate moisture reaching the metal surface.

What about contaminates in the compressed air?

i said to use clean air. You wouldn’t paint with dirty air, would you?

 

[Krondor]

Now if you had ever used that blasting cabinet on greasy/non clean materials. It is contaminated. And you would need to clean the material with a solvent, SSPC-SP1 Aka wax and grease remover after blasting. I doubt most people have a clean enough air system at home to remove all signs of oil from their compressor too.

I’m just giving my advise on what I was told by the professionals at an automotive paint supplier and the method I chose to prep my vehicle for paint.

 

[RUSH55]

Yeah, I’m still gonna clean it beyond just compressed air. Doubtful anyone would go through the trouble of using wax and grease remover or acetone on a rusty patch of metal prior to blasting, grinding, or sanding.

 

[Splangy]

Yeah, I’m still gonna clean it beyond just compressed air. Doubtful anyone would go through the trouble of using wax and grease remover or acetone on a rusty patch of metal prior to blasting, grinding, or sanding.

Doubtful? This is how all quality coating projects are specified. As I stated above, it seems odd to those who aren’t in the paint/coatings business, but this is how it works best.

If you’re just fine sanding the surface and an angular surface profile from blasting isn’t achieved, you can get away with solvent washing and wiping with a rag. However. You still want to always wash a part before blasting or sanding or you risk impregnating the substrate with matwriall which can jeopardize adhesion. If you’re wiping down a properly sandblasted pet with a rag, you’re asking for trouble. I went over this in my post above.

Look, none of this is necessary if you’re painting a steel decoration that will hang on the wall of your climate controlled house. We’re talking about parts that will potentially be exposed to severe conditions and The OP asked about the best way to prep the metal. I provided that answer and I don’t think it was all that unreasonable. In fact, in some cases, it could result in you simply working smarter and not harder.