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Underseal / bituminous coatings
https://www.ausmini.com/forums/viewtopic.php?f=2&t=90055		 Page 1 of 1
Author:  simonw [ Fri Jul 24, 2015 9:52 pm ]
Post subject:  Underseal / bituminous coatings
A question for the brains trust - why?

I hate the stuff , specially when restoring but it's so popular
Cheap and easy ?

Are there any alternatives for an underbody ?

Has anybody just undercoated and painted their 'bottoms'?

What does it do the dynamat or similar isnt doing inside ?

Some here have reported trouble painting over it and I have a mini in my shed full of dried and cracked black stuff and a floor full of rust ... So ... Why do we do it ?

Throw your 2c in lads
Author:  Bubbacluby [ Fri Jul 24, 2015 10:06 pm ]
Post subject:  Re: Underseal / bituminous coatings
Stones can hit it and it wont chip off and cause bare metal that will rust like will happen with paint.
Author:  peterb [ Sat Jul 25, 2015 9:03 am ]
Post subject:  Re: Underseal / bituminous coatings
I used the rubberised coating used on modern cars and the heat moulded (Bitumin?)mats on inside. I only have standard carpets with no underfelt and its all quite civilised inside. I have noticed 1 or 2 'chips' underneath since putting car back on road but nothing dramatic, probably happened when i drove over that Landcruiser the other day.
Author:  simonw [ Sat Jul 25, 2015 10:26 am ]
Post subject:  Re: Underseal / bituminous coatings
My point too peterb , land cruisers just need to learn their place .
But really, I think rust maintenance is probably easier on a painted surface than a bituminous surface . You can see it and deal with it.
How many times have we little 'suprises' with the black stuff.

Any brand of the moulded mats you used ?
Author:  peterb [ Sat Jul 25, 2015 4:39 pm ]
Post subject:  Re: Underseal / bituminous coatings
I got the stuff from the painter that did the car. Ask at your local paint/panel shop, they should have them. Just cut to size and cook 'em on with heat gun, looks like it came from factory.

Re the Land cruiser, it would have normally cleared but I didn't notice it had a lift kit and roof racks with some mountain bikes on them.
Author:  KLAS [ Sat Jul 25, 2015 4:44 pm ]
Post subject:  Re: Underseal / bituminous coatings
over here many restored cars just got paint covered with some (nearly) clear wax coat. as you mentioned to better see if it starts to rust again.
but most cars used every day get regular underseal if the owner don't want to spend much time under the car.

so it's up to you what you prefer
Author:  iansmini67 [ Sat Jul 25, 2015 8:05 pm ]
Post subject:  Re: Underseal / bituminous coatings
When we did my dads Moke project we used some stuff I got from the local automotive paint supplier but I cant at this time recall what its called. Its an under body sealer/stone guard but must be sprayed through a special gun, which I have. Well worth the investment.
The underfloor was preped to bare metal, treated with a de oxidine pre treatment, then etch primed. The under body sealer was then sprayed on. The finish is superb and leaves a fine ripply surface. Once dry the whole underside was primed in 2K ready for top coat. You can see too that the fine finish still reveals the spot welds of the body.

I did find that after the yellow was applied the black still seemed to show through. This was mainly because of the light coat of the undercoat. Maybe a thicker application would have been better. After several years on the road its held up really well and no rusty stone marks. I will be doing the same treatment on my S project shortly.

Ian

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Author:  simonw [ Sat Jul 25, 2015 10:37 pm ]
Post subject:  Re: Underseal / bituminous coatings
Awesome reply thanks Ian , just what I was looking for !
Author:  mickmini [ Sun Jul 26, 2015 11:21 am ]
Post subject:  Re: Underseal / bituminous coatings
I re-did the underside of my 1966 car in about 2009. What i noticed was that where the bituminous coating was intact, there were no signs at all of rust. The original brown rotodip primer was still intact and i did not remove it.

On the other hand, along the sides behind the wheels where 40+ years of throwing road debris up had worn away the bituminous coating, there was clearly signs of previous surface rust that had been cleaned up and simply re-primed and painted. There were chips and scratches in that paint that had surface rust. These areas i cleaned up, re-primed and recoated the whole underside with the bituminous coating.

My summary conclusion was that the original rotodip primer and coating system is good for more than 40 years of use as long as it is maintained intact.

As an aside, there were also areas immediately behind the engine bay, particularly behind the diff, where there was no bituminuous coating left, having been dissolved by oil leaks over many years. The presence of the leaked oil however kept the rust at bay. Oil leaks are not all bad ;-)
Author:  simonw [ Sun Jul 26, 2015 12:33 pm ]
Post subject:  Re: Underseal / bituminous coatings
Nice rebuild btw ;)
Author:  simonw [ Sun Jul 26, 2015 4:24 pm ]
Post subject:  Re: Underseal / bituminous coatings
Good points you raise Mick ..so I think particular attention needs to be paid to bits /area that are inflicted with most Road gunk - wheel wells , firewalls things like these
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