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Abrasive equivalent to scuffing for paint?

MWC

New Member
#1
I am in the process of doing a color change and am looking for the best approach for scuffing the engine bay. Everywhere I can I have been scuffing with 600 grit, but there are numerous nooks and crannies I want to make sure I scuff as well as I can that are difficult to reach with sand paper. Is there a mild abrasive I could load into a spot blaster that would be effective for this? I don't need to go to bare metal, I just need to make sure I have the best chances for proper adhesion over existing paint.
 
#2
I got talked into using corn cob once. Got a bunch of it that all I think would do would be a scuff, did not want to cut thru too much. Other than that, its just using whatever you can at a much lower pressure.
 
#3
You didn't specifically ask for this, but as an FYI, 3M scuff pads have "equivalent grits" that 3M lists. This is the path that I've gone to scuff up my stuff (not bare metal) prior to shooting it. I haven't had the car out in the elements yet, but haven't had any adhesion problems so far. The scuff pads are much easier to get into the hard spots that a piece of sand paper.

Here's some of the equivalent grits. There are a few different resources combined here, so there may be some conflation of stuff, but it should be close enough. Looks like the light grey or green pads are what you would want. Here's a link to an official 3M brochure.

Again, I know this isn't what you asked for, but maybe an alternative to making a mess with a sand blaster?
Cheers,
Chris
SCOTCHBRITE GRIT CHART
White - 1200-1500 grit
Light Grey - 600-1000 grit.
Green - 600 grit
Maroon - 320-400 grit
Brown - 280-320
Dark Grey 180-220
Tan - 120-150
 
#5
If you are sanding with 600, you are going directly to paint, and I don't think there is a blast media that would be right for that application for a few reasons. What you really want is gray scuff pads and maybe prep paste too, or Comet if you want to be thrifty.cut it into small rectangles, it is pretty good at getting into tight spaces with a little elbow grease.
 

MWC

New Member
#6
If I can get away without blasting that would honestly be better because it's just so messy. I'll have to pick up some 3M pads. I hear red mentioned all of the time here when talking about the 3M scuff pads, but would I be better served with green?

This spot where there's a crevice around some of the factory filler is what got me thinking about a scuff-like media but I can see how I can get in there with scotchbrite if I take my time.
 

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MWC

New Member
#7
For reference, this is the sort of finish I've been going for on the car prior to paint. The plan is to do a sealer coat of reduced epoxy, base, and then clear. There are places where I need to do some very light body work to fix some chips, small dings, etc. and for those I am going to use some un-reduced epoxy before the sealer coat. This is all my first time doing this kind of work and I'm trying to give myself the best chance for success.
 

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#8
If you are using sealer, then in the engine bay you can even use red scuff pads which are more aggressive than gray. The sealer should adequately fill the scratches. Engine bays tend to be oily/greasy, so a prep paste is highly recommended, or a bathroom cleanser like we used to use in the old days.

By the way, those crosshatch scratches look a little rough, what grit are they?
 

MWC

New Member
#9
Right at the beginning I was using 400 and later moved to 600 after spending more time reading through posts on this forum. You can see where I sadly burned through the clear completely in the bottom right corner of the 4th photo. I was thinking I could put a light layer of glazing putty down there to flatten it but I'm not sure if it's really worth it. I can get a better photo later.

If those scratches are a little deep I can definitely go back over it with some 600 to lightly smooth it down. I don't have much of a frame of reference here so pointing that out was helpful, thank you.

Is this the paste you're describing? https://www.amazon.com/3M-06013-Scu...8&qid=1549397091&sr=8-1&keywords=scuff-it+gel
 
#11
My personal opinion is that linear 400 scratches don't always cover with sealer, unless a heavier application is used along with some scuff sanding prior to paint to reduce texture. With a solid color it would not be a concern, but yours looks like a fine silver and those show every prep mistake.
 
#13
if you have a blast media supplier nearby that carries crushed glass, you can get that in a fine grade. its so fine in fact that it feels like baby powder. i dont use it often but i keep a few bags around for doing exactly what you are looking to do. this wont remove paint but it does take the shine right off. a firewall that you would have a couple hours in prepping with a scotchbrite, i can do in about 3 minutes. once its done just clean the surface up, shoot a sealer coat of epoxy primer and go right to paint.
 
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