Automotive

Repainting car bumper due to chips - how much sanding?

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  • Nov 15th, 2020 2:35 pm
[OP]
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Dec 31, 2007
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Richmond Hill

Repainting car bumper due to chips - how much sanding?

Edit - updated with results later in thread...

***

I sanded the worst spots where the chips were the largest.

Do I need to sand the entire bumper down to bare metal? Or enough to get adhesion with primer, even if there are still chips that can be felt, and those would be filled in by the primer?

Just wondering how much more sanding I need to do... Smiling Face With Open Mouth And Smiling Eyes

Not looking to do a showroom job, just good enough to not be noticeable after repainting is done.
Last edited by enwhyRFD on Nov 8th, 2020 3:39 pm, edited 1 time in total.
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enwhyRFD wrote: I sanded the worst spots where the chips were the largest.

Do I need to sand the entire bumper down to bare metal? Or enough to get adhesion with primer, even if there are still chips that can be felt, and those would be filled in by the primer?

Just wondering how much more sanding I need to do... Smiling Face With Open Mouth And Smiling Eyes

Not looking to do a showroom job, just good enough to not be noticeable after repainting is done.
Unless you're car is form the early 90's or earlier, it's highly unlikely you'll find a metal bumper under the paint, if you do see metal you just put a hole in your bumper and sanded to the rebar.
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Oct 25, 2020
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Filler putty would the simplest fix. Then sanding smooth.

What vehicle are you working on and are you planning to paint the entire bumper with a rattle can or paint gun?
[OP]
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BeaverLiquor wrote: Unless you're car is form the early 90's or earlier, it's highly unlikely you'll find a metal bumper under the paint, if you do see metal you just put a hole in your bumper and sanded to the rebar.
My mistake. Looks gray. But feels plastic.
[OP]
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MyGoToUserName wrote: Filler putty would the simplest fix. Then sanding smooth.

What vehicle are you working on and are you planning to paint the entire bumper with a rattle can or paint gun?
2010 Honda fit. Can. No gun.

The front edge of the hood has a 3" inch rust spot that i want to fix, so might as well do the bumper at the same time.

Also just so many chips and pits to fill so was hoping to avoid manually filling and sanding one pit at a time...
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Oct 25, 2020
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enwhyRFD wrote: 2010 Honda fit. Can. No gun.

The front edge of the hood has a 3" inch rust spot that i want to fix, so might as well do the bumper at the same time.

Also just so many chips and pits to fill so was hoping to avoid manually filling and sanding one pit at a time...
The bumper is plastic then.
It will be far more efficient to fill the damage and sand smoothly than it would to sand every stone chip down. A putty knife will do most of the work for you.

You can fill every spot at the same time, sand it smooth and move onto primer. Final sand then paint/clear.

Just be aware painting a large area like that with most rattle cans will end with a blotchy mess. Rattle can clear generally doesn't spray evenly. For a 3 inch spot you'll be fine.

2K clear being the exception, cans cost roughly double your typical 1k clear cans cost, but spray pattern is more even and because they include a hardener activator you end up with a more durable and UV resistant finish. Once activated the can is good for roughly 2 days.
It is worth researching if you want more info on 2k clear.
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It's a 10 year old bucket of bolts with plastic bumpers. Drive it until it pukes. Fix your hood issue and rip it.
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enwhyRFD wrote: 2010 Honda fit. Can. No gun.

The front edge of the hood has a 3" inch rust spot that i want to fix, so might as well do the bumper at the same time.

Also just so many chips and pits to fill so was hoping to avoid manually filling and sanding one pit at a time...
If you can feel the pits with your finger primer isn’t going to fill it. Doesn’t take much to putty and sand and those. Then primer the area. It will annoy you later if you don’t take the extra step knowing it wouldn’t have taken much effort.
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MyGoToUserName wrote: The bumper is plastic then.
It will be far more efficient to fill the damage and sand smoothly than it would to sand every stone chip down. A putty knife will do most of the work for you.

You can fill every spot at the same time, sand it smooth and move onto primer. Final sand then paint/clear.

Just be aware painting a large area like that with most rattle cans will end with a blotchy mess. Rattle can clear generally doesn't spray evenly. For a 3 inch spot you'll be fine.

2K clear being the exception, cans cost roughly double your typical 1k clear cans cost, but spray pattern is more even and because they include a hardener activator you end up with a more durable and UV resistant finish. Once activated the can is good for roughly 2 days.
It is worth researching if you want more info on 2k clear.
2k clear is a great product but you must use ***proper fresh air mask and ventilation techniques. A plain old N95 isn’t going to cut it. It’s highly toxic. Personally the health risks are too high for me.
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cartfan123 wrote:
2k clear is a great product but you must use ***proper fresh air mask and ventilation techniques. A plain old N95 isn’t going to cut it. It’s highly toxic. Personally the health risks are too high for me.
There are trade offs but for painting high impact areas(especially an entire bumper) I'd never bother with 1k.

I've done wheels, headlights, front lips with 1k and the finish doesn't hold up to debris etc.
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Ummm a home respray with a rattle can is going to look like SHIT. Leave the bumper alone.
[OP]
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Update on my first diy paint and rust fix job (not as good as chris fix obviously :D, but happy with overall results)
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Oct 21, 2006
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great job op, how much did the project cost?
[OP]
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2 spray cans mixed at carquest $35 each (not sure if this is a decent price, but didn't really have a choice.)

2 cans of primer $10 each
2 cans of clear coat $ 10 each
Bondo filler $20
Bondo glaze putting $10 i think
Putty knives $5?
Some sandpaper.

$150ish
[OP]
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Jigsaw wrote: great job op, how much did the project cost?
Thanks! Learned a lot on this project.
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Did you sand by hand?
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Any close up pics?
[OP]
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rngun wrote: Did you sand by hand?
Yes. I had left over sandpaper from a body kit so just used that. 60>220>800(dry+wet)

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