Use of bitumen underseal paint

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Snifflebag

Snifflebag

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Done a quick search, but can't see a consistently positive suggestion for undersealling, and posted this question on my sill thread, but thought it worth getting a wider range of opinions from the Great and Good of LZ!

Obviously Waxoyl provides some protection, but I was wondering about using bitumen paint such as that used on boats for the underneath of my new sills?

Obviously these areas are subjected to all kinds of damp/salt/rock etc abuse, so wanted to give them a reasonable level of protection over and above a thin layer of Waxoyl... views anyone?
 
THe problem I used to find with ordinary bitumen underseal was that it dries out and cracks eventually, allowing water to enter the cracks and rust the metal underneath. The most succesful method I have found if is, starting with the bare metal, and generous coating(s) of a zinc rich primer (having first cleaned up any rust and treated it with a rust converter), then use a compatible undercoat and top coat. Finally, apply a quality underseal which has both good adhesion qualities and remains soft. Waxoyl is one of a number which can work.

The key is regular inspection and re-coating if there are signs of wear, stone damage, or thinning of the underseal.
 
I have found the best protection is a good coating of an oil/grease mixture brushed on. Mix clean engine oil and grease to a soft brushable paste and brush on with a paint brush. It does not wash off, does not crack or chip off, and stays on even if the metal is not completely clean. And if after a time it needs recoating, just brush some more on. Mucky job to put on but in twenty years after I did our Discovery it has never failed an MOT or required welding.
 
Sheffield said:
I have found the best protection is a good coating of an oil/grease mixture brushed on. Mix clean engine oil and grease to a soft brushable paste and brush on with a paint brush. It does not wash off, does not crack or chip off, and stays on even if the metal is not completely clean. And if after a time it needs recoating, just brush some more on. Mucky job to put on but in twenty years after I did our Discovery it has never failed an MOT or required welding.
Click to expand...

park up on tarmac on a hot day could have a case of the drips
 
Sheffield said:
I have found the best protection is a good coating of an oil/grease mixture brushed on. Mix clean engine oil and grease to a soft brushable paste and brush on with a paint brush. It does not wash off, does not crack or chip off, and stays on even if the metal is not completely clean. And if after a time it needs recoating, just brush some more on. Mucky job to put on but in twenty years after I did our Discovery it has never failed an MOT or required welding.
Click to expand...
I use the dirtiest, ****tiest, grimiest used engine oil and just paint it on.

Any left over gets poured into the chassis!

FFS £20+ on new oils plus grease! :eek::eek: Some folks have too much dosh! :D:D
 
bitumen under seal is NOT a paint, it is not waterproof, it retains water, it is there to protect against impacts damage (stone chips e.t.c.), the coating under the bitumen needs to be fully sealed paint capable of stopping water penetration. If used correctly bitumen under seal is a very effective defence against corrosion, me personally I would use a heavy impact paint such as hammerite and then apply the bitumen over the top. It is not a rust inhibitor though and if you get stone chips through both layers then it will rust, you wont find anything though that will stop this, rust is a bastard and will always persevere unless your willing to continually check, clean and apply a coating of some sort...
 
Oldseadog said:
I use the dirtiest, ****tiest, grimiest used engine oil and just paint it on.

Any left over gets poured into the chassis!

FFS £20+ on new oils plus grease! :eek::eek: Some folks have too much dosh! :D:D
Click to expand...

I used to use old engine oil but got fed up of it getting all over my clothes every time I crawled/worked under my vehicle.
 
The problem with used oil is that it contains acids, water and other nasty things. Clean oil is safer and more effective. Mixed with grease to form a paste it stays put, and does not require a completely clean surface if it is to stay on, unlike paint or seals. Once the surplus had dripped off I never had any trouble with it making a mess of where ever the vehicle was parked. Unlike the steering box... It is also possible to re-coat the chassis in the future without having to completely remove the previous coating. The difficulty with paint and underseal, as has been mentioned, is their tendency to allow water to creep behind and become trapped under the coating, where it will cause corrosion faster than if there was no coating at all.
 
So the message so far seems to be get the basics right - good primer onto clean metal, followed by summat...

Don't fancy the old oil stuff to be honest. I spend too long under the vehicle and jet washing it after laning trips ... As a first step I'll paint primer, then Hammerite or vehicle paint and Waxoyl after that. I have all of the bits I need for that so can crack on as I finish.

I had assumed I would have to Waxoyl regularly since the jet washer takes it toll...

Thanks all
 
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Another thing I am looking into is grease for those bolts that get rusty and muddy underneath. I remember my dad telling me he used to use a maritime grease that goes sorta hard on the surface with a sort of whitish look to it. It's very easy to get off the bolt and underneath is in real good nick.

I'll post results when I can be buggered.
 
i pump dirty engine oil in my chassis every year. i block all the drian holes with foam ear plugs then pump in the oil with a garden sprayer.1995 defender never welded
 
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