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Under Coating, good? Bad? Pictures!


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Well these pictures are from a year ago right after installing my lift and before the fancy trussed 8.8 and driveshaft, I thought Ide share. I grinded every single little piece of rust off the underside and inside the fenders ( using a brass wheel on the gas tank) and the wiped the whole thing down with Acetone to get rid of anydust. Took proabily a total of 12 hours of hell and crap falling in my mouth and I was done and probabily spent another hour jnder the MJ admiring it! 42c08aba21b20554d043f8e7e537c42b.jpg222a376f1415e71c5d2d036dc2ef02d0.jpg So what are your guys oppinionanin undercoating? Any stories to tell? Pictures to share? :)

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I wouldn't put undercoating on bare cleaned metal. It should be painted first. Some people say undercoating will hold moisture but I've really only seen this in the salt belt where rust has creeped under the coating through damaged areas or seams. In the south I've seen no problems at all with using it for protection and sound deadening.

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After I media blasted the chassis of the my truck, I coated it in POR 15 followed by the POR 15 chassis coat. I had planned on leaving it as is but discovered a new POR 15 undercoating product. I applied the undercoating to the underside of floor boards in hopes it will dampen road noise.

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I wouldn't put undercoating on bare cleaned metal. It should be painted first. Some people say undercoating will hold moisture but I've really only seen this in the salt belt where rust has creeped under the coating through damaged areas or seams. In the south I've seen no problems at all with using it for protection and sound deadening.

I used a grey primer first, will that help?
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I think an enamel like rustoleum would be better as it is more water resistant than a lacquer primer. Primer is only meant to be a base for a resilient topcoat and not as a finish coat itself. I don't consider a rubberized undercoating as a resilient topcoat due to its softness. The undercoating should only used as an additional layer of protection.

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I live up in the rust belt of ohio, don't know about your location but up here I would avoid undercoating. There was a healthy coat of undercoating on my last XJ. I really thought the undercarriage looked good until I deciding to test it one day and found that although the undercoat appeared to be in good shape salt and moisture must have got underneath it and rotted out the entire floor. I believe that the salt and moisture creeps underneath unnoticeable cracks and gouges in the undercoat and becomes a trapped breeding ground for rust. I think this is a major problem here especially due to their new implementation of salt brine. This occurred even though I was washing the truck and undercarriage weekly. If you live in a salt area I would avoid undercoating as it hides your view of the actual metal.

 

I would suggest a coating of por15 and then a chassis coat of your preference, if you really want to coat the undercarriage in something to avoid further corrosion I recommend Fluid Film. It doesn't harden up like undercoating and it does wash off over time, but I have only applied it once this winter to the MJ and when I put the MJ up in the air and look at the underneath it still looks beautiful and you can watch the water and salt bead right off the surface.

 

If you don't live in an area prone to accelerated rusting I would think some por 15 and a quality too coat would be enough.

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I live up in the rust belt of ohio, don't know about your location but up here I would avoid undercoating. There was a healthy coat of undercoating on my last XJ. I really thought the undercarriage looked good until I deciding to test it one day and found that although the undercoat appeared to be in good shape salt and moisture must have got underneath it and rotted out the entire floor. I believe that the salt and moisture creeps underneath unnoticeable cracks and gouges in the undercoat and becomes a trapped breeding ground for rust. I think this is a major problem here especially due to their new implementation of salt brine. This occurred even though I was washing the truck and undercarriage weekly. If you live in a salt area I would avoid undercoating as it hides your view of the actual metal.

 

I would suggest a coating of por15 and then a chassis coat of your preference, if you really want to coat the undercarriage in something to avoid further corrosion I recommend Fluid Film. It doesn't harden up like undercoating and it does wash off over time, but I have only applied it once this winter to the MJ and when I put the MJ up in the air and look at the underneath it still looks beautiful and you can watch the water and salt bead right off the surface.

 

If you don't live in an area prone to accelerated rusting I would think some por 15 and a quality too coat would be enough.

I think an enamel like rustoleum would be better as it is more water resistant than a lacquer primer. Primer is only meant to be a base for a resilient topcoat and not as a finish coat itself. I don't consider a rubberized undercoating as a resilient topcoat due to its softness. The undercoating should only used as an additional layer of protection.

I might be in deep crap then cause I live in Missouri! Well I guess next time the floor boards rust out in the next 20 years ill go back and POR 15 it and do it the right way!
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