How to Fix a couple of spots sprayed with epoxy primer

R

ross52

Hi,

I sprayed my engine department with SPI epoxy in June 2020. I applied bondo to a spot on the frame rail (within the window), but haven't done anything else to it since. Then, I completely forgot to apply bondo to another spot on the shock tower, which is now well outside the window, then I ground the epoxy off the spot. (SEE PHOTOS) I want to finish these two spots and then spot prime them with epoxy. How do I do this and get acceptable results? Thank you

19BE35B1-BD78-423A-A502-78233DF91D33.jpeg92F314A6-AD57-40BD-9B54-D1F25946E0AE.jpeg2F9CE7E8-F145-46A7-AE07-266B71DD459E.jpegE374502B-BED5-4226-8D15-0056C2C0624A.jpeg
 
Say I do that, and after I'm done with the bondo, how do I blend some epoxy primer over the repair?
 
ross52 said:
Say I do that, and after I'm done with the bondo, how do I blend some epoxy primer over the repair?
Click to expand...

I think the only way it will work and look right is taping it at a line or seam and spraying an area. If you just spot it in the middle of the panel you will see the overspray haze line around it. So you have to find an area that has a good place to tape and not have it show. From there you will want to mask off anything you dont want overspray on.

One more thing to consider is the mapping of epoxy over filler. You will need probably a couple coats of epoxy over your filler once you are done with any sanding on it. From there you will want to sand/scuff with 320-400 or maroon scotchbrite making sure not to break through, and once your entire area to spray is scuffed evenly you can put on your final coats. You can spot in over your filler to save product as overspray haze will be scuffed off, but the final appearance coat needs to be put on at once.
 
sprint_9 said:
I think the only way it will work and look right is taping it at a line or seam and spraying an area. If you just spot it in the middle of the panel you will see the overspray haze line around it. So you have to find an area that has a good place to tape and not have it show. From there you will want to mask off anything you dont want overspray on.

One more thing to consider is the mapping of epoxy over filler. You will need probably a couple coats of epoxy over your filler once you are done with any sanding on it. From there you will want to sand/scuff with 320-400 or maroon scotchbrite making sure not to break through, and once your entire area to spray is scuffed evenly you can put on your final coats. You can spot in over your filler to save product as overspray haze will be scuffed off, but the final appearance coat needs to be put on at once.
Click to expand...

Hi sprint,

I agree with you regarding taping off at the seems. I was just hoping It could be spot repaired like you could with the old lacquer. What is "mapping of epoxy over filler"? Does it always happen and is there a way to prevent it? Is the final appearance coat, just one coat? How long after scuffing the first coats do I have have to put on the final coat?
Thank you for yo ur help with this.
 
Mapping refers to being able to see the outline and different surface of filler when top coated. The filler will absorb because its porous and has a different texture, this can show up in the above coats when using only epoxy as a finish coat. I cant say for sure if it always happens, maybe different fillers don't do it, but in my experience when using filler and then using the next coats of epoxy as your finish coat the outline could be seen. To prevent maybe using a finishing glaze over filler would work, I always just spotted with epoxy and got back to a uniform surface with it. I usually tried to do any final scuffing and cleaning as close to when I was going to top coat as possible to avoid any contamination. Any final appearance coat I always did 2 coats for the best durability.

Here is a pretty crappy picture of what it looks like.
20171018_122707.jpg
 
sprint_9 said:
Mapping refers to being able to see the outline and different surface of filler when top coated. The filler will absorb because its porous and has a different texture, this can show up in the above coats when using only epoxy as a finish coat. I cant say for sure if it always happens, maybe different fillers don't do it, but in my experience when using filler and then using the next coats of epoxy as your finish coat the outline could be seen. To prevent maybe using a finishing glaze over filler would work, I always just spotted with epoxy and got back to a uniform surface with it. I usually tried to do any final scuffing and cleaning as close to when I was going to top coat as possible to avoid any contamination. Any final appearance coat I always did 2 coats for the best durability.

Here is a pretty crappy picture of what it looks like.
View attachment 13261
Click to expand...

Hi sprint,

thank you for your advice.

Can you explain as specifically as possible what you meant by the comment below? Please include your definition of "spotting" the timing of these spot repairs in relationship to when you noticed the mapping and if there was any additional prep work etc, prior to the spotting etc.

"I always just spotted with epoxy and got back to a uniform surface with it"
 
Spotting is a spot repair over an affected area, so over your filler. Prep is the same as any other time as is anything else related to flash times, etc. Your just spraying a spot, which is fine to cover and seal as any overspray will be scuffed off when you prep for your finish coats.
 
sprint_9 said:
Spotting is a spot repair over an affected area, so over your filler. Prep is the same as any other time as is anything else related to flash times, etc. Your just spraying a spot, which is fine to cover and seal as any overspray will be scuffed off when you prep for your finish coats.
Click to expand...

sprint,

I think I understand, but to be sure let me say it back to you. First, mask everything you don't want overspray on, next, spot with two coats over finished bondo, next scuff the entire area and apply two finish coats of epoxy. One question, How long after I spot over the bondo, can I scuff it and apply the final coats?
 
Hi Ross,

The instructions below I copied and pasted right from the SPI Tech manual (It is on the home page of the web site - click "Products" then click "how to use" and it will open in another page. If you haven't seen it yet, print it up - I keep a copy in a 3 ring binder right in my garage, as I am new to the autobody world. It gives the basic do's and don't of each product.

Epoxy:

"Wet and Dry Sanding: If you need to sand a large area of epoxy, the epoxy will dry sand best after 12-16 hours. Wet sanding with moderate pressure can be done after about 4 hours depending on the amount of epoxy applied, air temperature and substrate temperatures."
 
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