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#1 |
Registered User
Join Date: Apr 2015
Location: Chicago Illinois
Posts: 31
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Is undercoating good or bad ?
I was planning on coating all my patch panels with 3m undercoating where it won't be getting welded, like my cab mounts, and rockers on the inside where it won't get welded. I Thought this would be good to prevent future rusting out of these troubled areas, however I was talking to a mechanic at work and he said undercoating causes more rust because the moisture can get trapped underneath and expedite rusting. Looking to see if anybody has had good or bad issues with undercoating ?
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#2 |
Registered User
Join Date: Oct 2008
Location: Marianna Arkansas
Posts: 7,269
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Re: Is undercoating good or bad ?
I think your guy has it wrong the undercoating prevents the moisture getting next to the metal. But with that being said if you put it on and weld close to it it can/will melt away from that area. If you leave a big portion untreated so not to get burned what would be the use in some if not all? My ideas I will submit is to use weld through primer then you want extend it out past the areas to be welded then undercoat the parts away from the heat. Or treat the entire panel with weld through. Any way you go is a better than what they had as in nothing.
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#3 |
Registered User
![]() Join Date: Jun 2012
Location: springfield mo
Posts: 3,075
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Re: Is undercoating good or bad ?
Just get an oil leak like I got, it'll undercoat everything for you! Haha
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United States Marine Corps 2000-2011 Iraq and Afghanistan veteran Just living life now and enjoying it and my wife, daughter and son ![]() |
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#4 |
Senior Member
![]() Join Date: Oct 2009
Location: Godley, TX
Posts: 17,963
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Re: Is undercoating good or bad ?
If you've got it rust free and are gonna park it inside - I'd skip the uc. If you're gonna drive it in salt, might consider it, otherwise no. Might want to look for another mechanic... JUST kidding. Actually, maybe he's onto something - several of these trucks I've seen that had uc, I noticed when I peeled it's dry, rotted, mess off that there was rust underneath. Hmm. Ok, give that man a raise. Bottom line, I wouldn't undercoat it anyway.
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#5 |
Registered User
Join Date: Aug 2015
Location: agawam ma
Posts: 32
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Re: Is undercoating good or bad ?
3M undercoat will cost a lot , its not cheap, what I use is non fibered roof tar mixed with a little gasoline, it is a real petroleum product ,the gasoline aides in drying, you can handle it in about a hour, dries like paint, spray out of a body shutz gun, a gallon at home depot is around 16 bucks an goes a real long way
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#6 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,216
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Re: Is undercoating good or bad ?
I think black satan paint looks a lot better. If the metal has surface rust, spray it with Rustoleum Rusty metal primer.
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#7 |
Registered User
Join Date: Apr 2015
Location: Chicago Illinois
Posts: 31
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Re: Is undercoating good or bad ?
I was mainly planning to do it on the inside of the cab mounts/ supports since I have access and am putting new ones. They seem to rust out on the bottom and sides from debri so I thought it might be a rust deterrent.
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#8 |
Registered User
Join Date: Aug 2014
Location: kentucky
Posts: 111
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Re: Is undercoating good or bad ?
Undercoat has been used for years and worked very well. However it gets dirty and hard to clean. If you like the look and can handle the dirty look after awhile I say go for it.
If you're stripping it , painting the bottom of the cab and doing a detailed job , why cover it up ? I painted the bottom of my 67 red but my 71 I just sealed and painted it flat black. |
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#9 |
Registered User
Join Date: Mar 2012
Location: Evanston
Posts: 304
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Re: Is undercoating good or bad ?
Good undercoating is fine but expect it to become dirt colored. I prefer por15 and I use 3m aerosol undercoating for the places you just can't reach like the insides of cab corners ect. It is possible for the undercoating to cause problems. I have a utility bed that was undercoated and the whole bottom is rusted away. When you peel the undercoating back it's full of dirt and rust. But who knows how it was prepped before hand
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My Patinia'd 69 69-http://67-72chevytrucks.com/vboard/showthread.php?t=517537 My RHD 68 http://67-72chevytrucks.com/vboard/s...d.php?t=594928 |
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#10 |
Registered User
Join Date: Feb 2012
Location: Salado, Texas
Posts: 1,418
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Re: Is undercoating good or bad ?
The only parts on my one owner short step that weren't rotted away were under coated. If you get your parts nice and clean hit then with some primer weld everything up and a second coat of primer and then undercoat. Make sure you get every area covered and covered well. Where you see problems is where a section doesn't get covered and then the rot starts. Undercoating is a must if you're going to drive it.
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Just trying to figure this out... 1970 SWB Step-Side http://67-72chevytrucks.com/vboard/s...d.php?t=552980 1970 LWB http://67-72chevytrucks.com/vboard/s...d.php?t=584499 1970 SWB One Owner Step Side 6.0 LY6/6L90 http://67-72chevytrucks.com/vboard/s...d.php?t=617630 Junkyard's 1971 short wide http://67-72chevytrucks.com/vboard/s...86#post7531186 |
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#11 |
Registered User
Join Date: Dec 2009
Location: bisbee, arizona
Posts: 1,529
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Re: Is undercoating good or bad ?
under coating was good...even 43 years ago in AZ. so it cant be bad for the next 43 years either.
inside the cab... On a hot day? things could get kinda messy |
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#12 |
Registered User
Join Date: Aug 2012
Location: Topeka Kansas
Posts: 2,655
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Re: Is undercoating good or bad ?
Buy a small can of POR-15 and coat liberally and it likely won't ever rust again.
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#13 |
Registered User
Join Date: Jan 2009
Location: San Antonio, Texas
Posts: 1,374
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Re: Is undercoating good or bad ?
I will say that the areas under the bed which had good covering of the original undercoat, the metal under it was very clean. It was a bear getting the stuff off, but it convinced me of the value. Unfortunately, the application of the factory undercoat was "haphazard" at best.
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1972 C10 LWB, 350/350 Deconstruction began 5/2009, mostly completed restoration, 5/2017 |
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#14 | |
Registered User
Join Date: Jun 2011
Location: Osceola, Ia
Posts: 2,017
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Re: Is undercoating good or bad ?
Quote:
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Shawn 68 chevy K/20 05 chevy 3/4 4x4 71 short step-sold ![]() 71 chevy Beauville van My build. http://67-72chevytrucks.com/vboard/s...d.php?t=633039 |
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#15 |
Registered User
Join Date: Apr 2015
Location: Chicago Illinois
Posts: 31
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Re: Is undercoating good or bad ?
I'm planning to use raptor liner for the entire bottom of the cab as well as the floor inside, I love the look and I've heard great things. I think I'm gonna go for it and use the 3m aerosol can to coat the inside of my cab supports, cowl ( while I have it open for repair), and any other areas I won't be able to get with the rapor liner
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#16 |
Registered User
Join Date: Jul 2015
Location: North East PA
Posts: 682
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Re: Is undercoating good or bad ?
I would use short strain fiberglass( cat hair) on your floor patch seams as a base this will fill and seal all your small gaps and pin holes then prime and top coat with your choice
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#17 |
Registered User
Join Date: Sep 2013
Location: Pleasant Ridge, MI
Posts: 285
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Re: Is undercoating good or bad ?
I can only say what some others above have said about undercoating: it preserved the heck out of my truck. The original undercoating (either factory or Ziebart back in October 1970 when the truck was purchased) did one hell of a job keeping my truck clean. It is a slight pain to use a heat gun and mineral spirits to clean it up, but once it is clean, man the results are surprising. I mean over 45 years later and metal and paint are pristine. Unbelievable.
Phil http://67-72chevytrucks.com/vboard/s...d.php?t=657946 |
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