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Sand before undercoating?

hpva

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I plan on applying rubberized undercoating to the pinch weld of my 2023 Gladiator. Should I sand the paint on the pinch weld first before applying the undercoating or spray it right over the painted surface?
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Hootbro

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Quite honestly, the paint is giving its best protection there. Rubber Undercoatings have a bad habit of cracking and letting in the elements and causing rust jacking under the coating that will go years undetected and then it is too late. Scuffing the paint is just going to accelerate that.

I would recommend a yearly application of fluid film rather than rubber undercoating
 

chorky

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Fluid film is great but really messy. Another option that I opted for is amsoil HD metal protect. It dries like a wax. Not as good as the fluid film but also not messy


and dont forget 3m cavity wax for inside the frame.
 

LouisvEarlleJT

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I plan on applying rubberized undercoating to the pinch weld of my 2023 Gladiator. Should I sand the paint on the pinch weld first before applying the undercoating or spray it right over the painted surface?
That plan will end up with more rust down the road.

Idk what your typical vehicle use is, but I live in an area that uses salt like it’s free. -A regular (every couple weeks) trip to a self-serve car wash will keep rust at bay. Keeps all the crud sprayed out underneath and in the crevices.

Then, come spring, you spend ~30 mins with a wire brush and a spray can of gloss black underneath to touch up any chips/scratches on the frame.
 
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hpva

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That plan will end up with more rust down the road.

Idk what your typical vehicle use is, but I live in an area that uses salt like it’s free. -A regular (every couple weeks) trip to a self-serve car wash will keep rust at bay. Keeps all the crud sprayed out underneath and in the crevices.

Then, come spring, you spend ~30 mins with a wire brush and a spray can of gloss black underneath to touch up any chips/scratches on the frame.
My truck is white and the reason I was going to spray the pinch weld with black undercoating is because I installed power running boards and the pinch weld sticks out like a sore thumb.If the pinch weld is black it will blend in with the running boards.I was thinking if I used blank paint it would get chipped from the tires kicking up debris from the road whereas stones and debris would bounce off of the rubberized undercoating and be less likely to chip.
 

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BearFootSam

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Rubberized undercoating is widely considered to facilitate rust when water inevitably gets underneath and stays there protected by your undercoating.
Fluid film is a mess but you can really just spray it over whatever underneath the truck after a blast off at the car wash (dry of course). It's not a paint so it doesn't crack or flake, it flows when warm so tends to be self healing.

Once you put a good coat of wax on the paint and spray the undercarriage with fluid film, all you need to do during the winter is use the spot free rinse option at the DIY car wash over few weeks over the winter and everything will be good.
 

LouisvEarlleJT

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My truck is white and the reason I was going to spray the pinch weld with black undercoating is because I installed power running boards and the pinch weld sticks out like a sore thumb.If the pinch weld is black it will blend in with the running boards.I was thinking if I used blank paint it would get chipped from the tires kicking up debris from the road whereas stones and debris would bounce off of the rubberized undercoating and be less likely to chip.
If you have running boards then those will keep the rocks at bay. Black paint will ensure that it blends like you want and also that it doesn’t turn into a rusty mess.

Plus undercoating does weird things when exposed to UV/sunlight.
 

Gvsukids

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My truck is white and the reason I was going to spray the pinch weld with black undercoating is because I installed power running boards and the pinch weld sticks out like a sore thumb.If the pinch weld is black it will blend in with the running boards.I was thinking if I used blank paint it would get chipped from the tires kicking up debris from the road whereas stones and debris would bounce off of the rubberized undercoating and be less likely to chip.
If you have running boards then those will keep the rocks at bay. Black paint will ensure that it blends like you want and also that it doesn’t turn into a rusty mess.
Mud flaps help too. Otherwise don't drive the truck.
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