Best spray can undercoat, suggestions

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Best spray can undercoat, suggestions

Postby celigts » Wed Apr 18, 2012 1:50 am

So I'm desperately going to try and repair the underneath of my car. Past owners must have driven the car in winters before me cuz there is rust all over an bolts are snapping as easily as I drink my beer ;)

So planning on sand blasting the underside of the car in sections and recovering it with por15 then a type of rock liner but in a spray can cuz I can't afford a compressor or the place to do it. So spray can it is.

So any suggestions would be awesome :)
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Re: Best spray can undercoat, suggestions

Postby l0ch0w » Wed Apr 18, 2012 2:02 am

there are plenty of "rhino liner" knock off spray products out there :) From what i understand, most are essentially the same, its all about how well you prep the surface prior to application.
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Best spray can undercoat, suggestions

Postby celigts » Wed Apr 18, 2012 2:05 am

Yea there are. Some paint on and some cans.

How should the surface be prepped for the best finish result?

Also what should I avoid spraying? Atleast avoid with the rock liner.
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Re: Best spray can undercoat, suggestions

Postby bridge47 » Wed Apr 18, 2012 4:23 am

You could try this.

http://www.por15.com/RUBBERIZED-UNDER-C ... info/RUCS/

Perhaps it is the same stuff that's down at NAPA, but there you go.

Will you be using the 'silver' por15 product? The one with metal filler that is good for sandblasted surfaces?
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Best spray can undercoat, suggestions

Postby celigts » Wed Apr 18, 2012 7:18 am

Honestly I'll be going into this knowing nothing and having just heard of por15 lol. So I'll see how it goes
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Re: Best spray can undercoat, suggestions

Postby phattyduck » Wed Apr 18, 2012 4:42 pm

Make sure your 'base' coat is a hard/epoxy type product (POR15, or others). You can then use a rubberized cover coat over that if you want, but it may wear out/crack over time (I've rubbed/worn off the undercoating on the frame rails and wheel wells of my WRX a few times - I have to re-do it every few years).

I bet you can find tons of info on a place like the autogeek forums or similar. Some more general place where people are crazy about detailing/looks of their cars, even the underside.

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Re: Best spray can undercoat, suggestions

Postby Sifu » Thu Apr 19, 2012 3:27 am

There are homemade recipes with roof tar (cheap), oil, kerosene and sand that you can spray. I used to have a recipe somewhere but I can't find it since I've redid my PC system.

Yes these will wear out over time but I know the rubber spray cans will wear out much sooner and it's a pain to remove. A tar mixture will need to be reapplied but the way I look at it getting under the car and checking everything is good measure anyways. My MR2 had previous spray can liner and removing that stuff was a PITA (wire brush, sanding disks, sanding by hand the wheel arches with the suspension still on... Not fun). Flakes off and damn what a mess. The hard to reach stuff I just said fugg it and put POR15 over it; I hope it doesn't come back to haunt me.

I'll probably put a tar undercoat on top of the POR15 to help repel water, dirt, dead animals, etc. but if you can I'd say no to the spray can stuff. As I don't know what kind was used I can't fully say it's the wrong route but seeing it flake off I know it didn't work and it can make things worse (trapping water, salt, dead animal matter in pockets).
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Re: Best spray can undercoat, suggestions

Postby l0ch0w » Thu Apr 19, 2012 4:03 am

^ i believe the Brits and the Aussies call that a bitumen coating :)
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Re: Best spray can undercoat, suggestions

Postby Street_Chally73 » Fri Apr 20, 2012 8:11 am

I've used 3M's Professional Grade Rubberized Undercoating on several vehicles now & I would have to say it has held up very well considering the cost (~$10-$12/can at Napa Auto Parts) and it covers well (just don't apply it too heavy between coats or it will run/drip). It certainly won't be as hard to the touch if you were to use a designated bedliner coating, but it will replicate the factory undercoating quite well in that it will stay flexible, absorb some of the road noise from the floor pans, and it won't flake/chip off easily. I would probably every now & then keep an eye on the areas that receive the most contact with road debris on a daily basis (mainly the wheel well openings), but other than that the stuff will last & should protect the underbody from any rust.

I know you're not going to like this part, but realistically the only way to get the existing undercoating off prior to blasting the rusted area(s) is by using a combination of chemical or mechanical work to remove the majority of it. Sandblasting, while very useful for cleaning rusted metal, does not work well when attempting to remove any tar or gooey material (it actually just makes it worse if you ask me 'cause it makes it even more gooey & consequently harder to remove). What you'll end up having to do is either remove it chemically with something that can eat away at the undercoating's bond to the metal OR you'll have to do it mechanically.

I haven't really used the chemical approach to it before, but I can say that the mechanical way is very effective. Unfortunately, it really is time-consuming & somewhat tedious in hard-to-reach areas that your tool of choice can't effectively hit. When I did my Challenger's underbody in preparation for repairs & paint, I used a combination of a wire wheel cup on a 4 1/2" angle grinder (make sure you have PLENTY of layers on to cover your body & safety goggles & even a face shield are a MUST!!!), otherwise you'll end up with a ton of metal splinters all over your body as they continue to break off the cup at very high speeds.

The other tool was very handy, though I certainly wouldn't have had access to it if I didn't personally know the shop owner ($$$$). It's Snap-On's "Crud Thug", which was a pneumatic tool that has fiberglass(??) flapper discs on the end of a super light, glorified die-grinder looking tool (very little hand fatigue!!). That thing worked amazingly well getting into any of the small crevices I missed from the night before with the wire wheel cup, but just know that it is quite an expensive tool (especially if you're only going to use the thing once or twice).
Actually found it on their website (it's gone up some, lol):
http://buy1.snapon.com/catalog/item.asp ... ir=catalog
:shock:

I wouldn't even attempt to sandblast the underbody until you have the majority of the undercoating removed or else it will just turn into a gooey mess that's even harder to clean off than before (ask me how I know, lol). :twisted:

Since you plan on spot blasting the underbody, I would probably look at getting a quality product down as your base (POR-15 or an Eastwood base coating, such as chassis black, etc.), allow ample time for it to cure properly (whatever the manufacturer's recommendations are depending on which one you use), and then top-coat it with some 3M rubberized undercoating & it should stay clean & rust-free for many years. 8)

Good luck with it! :D
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Re: Best spray can undercoat, suggestions

Postby l0ch0w » Fri Apr 20, 2012 4:16 pm

The asphalt bitumen coating on the bottom is pretty much the longest lasting stuff you can put on underneath there... Its time consuming and messy to do, but its also by far the cheapest solution to re-doing the undercoat on your car. Plus you dont have to take off the old stuff...

BTW, fastest and cleanest way to remove that undercoating is with a dry ice blaster...
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Re: Best spray can undercoat, suggestions

Postby phattyduck » Fri Apr 20, 2012 4:46 pm

Street_Chally73 wrote:The other tool was very handy, though I certainly wouldn't have had access to it if I didn't personally know the shop owner ($$$$). It's Snap-On's "Crud Thug", which was a pneumatic tool that has fiberglass(??) flapper discs on the end of a super light, glorified die-grinder looking tool (very little hand fatigue!!). That thing worked amazingly well getting into any of the small crevices I missed from the night before with the wire wheel cup, but just know that it is quite an expensive tool (especially if you're only going to use the thing once or twice).
Actually found it on their website (it's gone up some, lol):
http://buy1.snapon.com/catalog/item.asp ... ir=catalog
:shock:

Good luck with it! :D
I'm going to second the Crud Thug - A shop-owner friend of mine has one and swears by it. He told me about it without me asking! Too bad its out of reach for a 'normal' person, really.

-Charlie
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Best spray can undercoat, suggestions

Postby celigts » Fri Apr 20, 2012 6:25 pm

Yea at that price it's not worth it to me ! Picking up some por15 today! And some final wipe so I can prep for primer. Probably won't e painting the car this year. If I do it'll be spray can lol!
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Re: Best spray can undercoat, suggestions

Postby Hotrodhendrix » Mon May 07, 2012 2:09 pm

I used Rhino liner in my engine bay. Had it in the VR4 and alltrac. No issues. but it does have a much more bumpy finish than most.
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Best spray can undercoat, suggestions

Postby celigts » Mon May 07, 2012 3:24 pm

Hotrodhendrix wrote:I used Rhino liner in my engine bay. Had it in the VR4 and alltrac. No issues. but it does have a much more bumpy finish than most.
~James


In the engine bay!
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Re: Best spray can undercoat, suggestions

Postby ZeroDrift » Mon May 07, 2012 3:51 pm

Best way to remove tar and similar materials is by making them super cold. The adhesion decreases and the material comes off in very large pieces. Dry ice works well for this if you can figure out how to keep it against the tar.

I've also used a roll-on bed liner product in my engine bay before. It worked out very well as it prevents the paint from chipping during tool impacts. Only advice with this is to prepare the surface as best you can. This goes a long way to promote proper adhesion.
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