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Underbody Corrosion - How To Avoid When Living By The Sea?


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#1 markwb

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Posted 31 October 2021 - 11:19 AM

Hi all

I’m very close to buying a 1990 model that has a very solid underbody with no history of welding or issues under there.

My concern is a big one - I live very close to the sea (200 meters or so) and only have a driveway to keep the car over winter.

Looking for advice as to what I can do to prevent the sea air and harsh winter weather from eating this car from underneath. The weather here can get fairly extreme at its worst. I’m very keen to put as much effort in as is necessary.


Edited by markwb, 31 October 2021 - 03:58 PM.


#2 sonikk4

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Posted 31 October 2021 - 03:37 PM

Hi and welcome to TMF.

 

There are a plethora of products out there that can help you BUT like any of them its all down to preparation.

 

My choice would be Dinitrol and their various products. (something we use in Civil Aviation.) Bilt Hamber is another good product. Waxoyl is still good as well. You will hear detractors but its easy to apply.

 

Now to the crux of the matter. If your car has had no welding or is not rusty at all???? then it has lead a very sheltered life or the previous owner was fastidious about maintaining it.

 

Yes they do exist cars like this but knowing from personal experience they are rare to be totally rust free. However i digress, so the best thing to do is get the car on a set of ramps / four poster etc to have a really good look for anything at all. Primarily you are looking at the underfloor in total, heelboard, boot floor etc etc. Look for anything flaking or lifting at all, dont just brush over it. Now if all of this is solid your next job it to properly clean it, get up into all of the nooks and crannies and then dry it off (dont be tempted to apply anything even if it says it can be applied over wet/damp areas.)

 

So baring in mind now that this process is for a car that needs no work other than applying a wax based protection product. Depending on what you purchase you need to make sure its applied to all exposed areas and also right into all of the little corners and areas where muck will accumulate. Be patient and particular in how you do this to get the best protection (no spray and pray application) Once done, clean off any excess. 

 

Now there are areas like the following where your particular product will need to be injected. Inner sills, A and B posts, front bulkhead crossmember, rear valance closeouts, seat crossmember, the rear subframe. You can access all of these areas although the bulkhead crossmember is the the most difficult and will need some lateral thinking on the best approach (front footwells, tucked up under the lower dash rails there is a cutout one each side.)

 

The inner /outer sill can be accessed via the flutes in the outer sill. Be very liberal with your application here to ensure you get the best protection possible. The rear valance closeouts normally have drain holes in them so use these but make sure once done they are clear to allow any moisture to drain out. The A and B posts are best done from inside the car and may need some trim items to be removed. The floor crossmember has a few holes that can be used to pump your product into.

 

The rear subframe. this is notorious for collecting detritus so it really needs to be thoroughly cleaned. Once done liberally apply your product into every gap you can see. The front subframes are normally very easy to access and what you see is what you get. (engine oil from any leaks helps to maintain them)

 

Doors, boot lid and bonnet. The doors will need coating inside, so take off the door cards, carefully remove the plastic liner enough to get access then pump in the product. Do make sure the drain holes are kept clear. Reassemble everything ensuring the plastic membrane is fully sealed on. This is important.

 

The boot lid is easy to do when its opened. The bonnet depending on whether its a roundnose (which your car will be ) or a clubby will need some careful application into the underside bracing.

 

So for a straight fwd on the road car process, then that is pretty much it.

 

So next (yes there is more and it depends on the underside finish) The underside as it currently is. Is it painted?? is it stone chipped?? Is it covered in wax based product??

 

If its painted and i mean by painted onto metal and nothing else then the wax based products are what you need. But obviously you need to ensure there is no bare metal / damaged paint at all.

If its stone  chipped (so a mottled rough looking rubbery finish) a couple of things here to think about. If any of it is flaking at all then that affected area needs to be removed (a wire cup on a grinder will do the job) until its all solid. You can buy spray cans of stone chip to re apply to those affected areas. Apply a topcoat of paint after if has been painted. Now you can apply a light clear coat of a wax based product to all of it for extra protection.

 

If its covered in a dark / black wax based coating, this makes checking anything underneath impossible to really determine its state. But if you are happy there is nothing dubious lurking there, any areas where its missing, thinned down, just apply some more.

 

Quite a lot to think about but its in the cars best interest to make sure there is as much protection as possible. Giving the car regular washes especially underneath paying particular attention to the front inner wings right up under the scuttle corners, the rear subframe and so on.

 

Ideally when at home the car needs to be under cover if possible, but if not you can get external covers to help protect your pride and joy.



#3 markwb

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Posted 31 October 2021 - 04:05 PM

Thanks so much for this, I really appreciate it. I believe the car has led a pretty sheltered life (literally), particularly the past decade where it’s added barely any mileage - though it’s flown through MOTs every year with minimal fuss. 
 

If I do get the car - and it’s likely I will - I’ll pay close attention to your guidance here. It really helpful. Thanks again for taking the time.



#4 Tornado99

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Posted 31 October 2021 - 04:45 PM

I'm using FluidFilm to undercoat my '88. This is a lanolin based protective spray, an improved type of WoolWax. Seen a few online reviews of people using in on modern cars in the rust belts here in North America, driving hard in 4-6 months of heavily salted roads. One guy shows what happens to areas he intentionally left some areas untreated, lots of scaly rust building up within a a year or two. Treated areas, just like new. This stuff creeps into all the seams well. Resists stone chip and spray effects. Cannot flake off b/c it remains as an oil/wax layer, not a paint.
Stay away from paints/rubberized treatments b/c these eventually bubble and flake, trapping moisture leading to rapid metal rot.

I will be re-applying the FluidFilm yearly.

Edited by Tornado99, 31 October 2021 - 04:46 PM.


#5 sonikk4

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Posted 31 October 2021 - 04:55 PM

I'm using FluidFilm to undercoat my '88. This is a lanolin based protective spray, an improved type of WoolWax. Seen a few online reviews of people using in on modern cars in the rust belts here in North America, driving hard in 4-6 months of heavily salted roads. One guy shows what happens to areas he intentionally left some areas untreated, lots of scaly rust building up within a a year or two. Treated areas, just like new. This stuff creeps into all the seams well. Resists stone chip and spray effects. Cannot flake off b/c it remains as an oil/wax layer, not a paint.
Stay away from paints/rubberized treatments b/c these eventually bubble and flake, trapping moisture leading to rapid metal rot.

I will be re-applying the FluidFilm yearly.

 

With regards to your paints / rubberised treatments. This is all down to preparation and of course what the state of the metal was like to start with. Plus when you use Stone Chip, at a minimum there needs to be a coating of epoxy primer underneath it in the event of a chip out of it. Its very resistant to stone chipping and most manufacturers use an equivalent.

 

That can be equally said about ANY product you use.

 

PPPPP. Preparation Prevents Piss Poor Performance.



#6 markwb

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Posted 31 October 2021 - 05:19 PM

Would using a service like this be a good use of money possibly? This place is only a short drive away from where I live. I’d be happy to pay to get things done properly, but only it’s actually going to genuinely make a difference.

 

http://rustproofing.wales/



#7 sonikk4

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Posted 31 October 2021 - 05:58 PM

Light rust removal??? that made me laugh. 

 

With a mini if you see rust generally it starts from the inside out. However if they follow that process they say then its quite comprehensive. However i would be looking for recommendations from previous purchasers as reviews are everything.

 

Back in 1979 i used to work for a company who did just this but it was on brand new cars literally straight from the factory. Every car was steam cleaned to start with, allowed to dry and then we would strip panels and trim off as required. All cavities injected, sealed then the underside coated. Followed by handwash with white spirits to remove any residue then steam cleaned. They then had the option to have a glaze polish applied.

 

I never found out how long it lasted for as cars of that era tended to rust straight out of the box. (think Alfas and Lancias)

 

Ziebart was another popular application which my 74 clubby had applied from new. That stuff was a swine to remove before i restored my shell. It literally stuck the smelly stuff to a blanket.

 

My resto, i have fully epoxy primed the complete underside of the car, seam sealed, Gravitex Stone Chip followed by topcoat (Project Paddy in my signature) Doors injected with Dinotrol along with the inner sills A posts and B posts. Front bulkhead crossmember as well.



#8 markwb

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Posted 31 October 2021 - 06:22 PM

You’re definitely right there - I’d be curious to know what previous customers have to say, I’ll look into that.



#9 Tornado99

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Posted 31 October 2021 - 07:01 PM

 

I'm using FluidFilm to undercoat my '88. This is a lanolin based protective spray, an improved type of WoolWax. Seen a few online reviews of people using in on modern cars in the rust belts here in North America, driving hard in 4-6 months of heavily salted roads. One guy shows what happens to areas he intentionally left some areas untreated, lots of scaly rust building up within a a year or two. Treated areas, just like new. This stuff creeps into all the seams well. Resists stone chip and spray effects. Cannot flake off b/c it remains as an oil/wax layer, not a paint.
Stay away from paints/rubberized treatments b/c these eventually bubble and flake, trapping moisture leading to rapid metal rot.

I will be re-applying the FluidFilm yearly.

 

With regards to your paints / rubberised treatments. This is all down to preparation and of course what the state of the metal was like to start with. Plus when you use Stone Chip, at a minimum there needs to be a coating of epoxy primer underneath it in the event of a chip out of it. Its very resistant to stone chipping and most manufacturers use an equivalent.

 

That can be equally said about ANY product you use.

 

PPPPP. Preparation Prevents Piss Poor Performance.

 

Sure, agree that prep is critical to paint type coatings...but the problem here is this is an underbody or even a cavity situation....there is no way to fully prep such areas and especially so on an older car with all sorts of previous coatings, damage, etc in all the little cracks and crevices. There's no way to get at those areas to perform proper prep work for painting.Yes you can slap/spary on a coat or two but unless the surface is properly prepared, it will flak/peel with a few years, trapping water/salts etc. 



#10 Tornado99

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Posted 31 October 2021 - 07:14 PM

Some of the video reviews, multi-year term real world tests of FluidFilm:

 

 

 

 



#11 Steve220

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Posted 31 October 2021 - 08:15 PM

A close mate of mine lives by the coat in north scotland. We took the subframes off and pumped them full of Bilthamber Dynax S50 (black), and all the places salt could hide with Dynax SC (clear) and Dynax UB. That was 4 years ago and it's still mint underneath.

 

https://bilthamber.c...oduct/dynax-ub/


Edited by Steve220, 31 October 2021 - 08:16 PM.


#12 dyshipfakta

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Posted 03 November 2021 - 08:16 AM

Waxoyl and used engine oil mix is what I have always used. A fella I know uses it on a Ferguson grey from the 30s and it’s never let him down. Obviously very messy so not for the neat freaks but my car although garaged goes out in all weather and rust hasn’t appeared anywhere.

#13 unburntfuelinthemorning

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Posted 13 November 2021 - 09:39 PM

Hi and welcome to TMF.

 

There are a plethora of products out there that can help you BUT like any of them its all down to preparation.

 

My choice would be Dinitrol and their various products. (something we use in Civil Aviation.) Bilt Hamber is another good product. Waxoyl is still good as well. You will hear detractors but its easy to apply.

 

Now to the crux of the matter. If your car has had no welding or is not rusty at all???? then it has lead a very sheltered life or the previous owner was fastidious about maintaining it.

 

Yes they do exist cars like this but knowing from personal experience they are rare to be totally rust free. However i digress, so the best thing to do is get the car on a set of ramps / four poster etc to have a really good look for anything at all. Primarily you are looking at the underfloor in total, heelboard, boot floor etc etc. Look for anything flaking or lifting at all, dont just brush over it. Now if all of this is solid your next job it to properly clean it, get up into all of the nooks and crannies and then dry it off (dont be tempted to apply anything even if it says it can be applied over wet/damp areas.)

 

So baring in mind now that this process is for a car that needs no work other than applying a wax based protection product. Depending on what you purchase you need to make sure its applied to all exposed areas and also right into all of the little corners and areas where muck will accumulate. Be patient and particular in how you do this to get the best protection (no spray and pray application) Once done, clean off any excess. 

 

Now there are areas like the following where your particular product will need to be injected. Inner sills, A and B posts, front bulkhead crossmember, rear valance closeouts, seat crossmember, the rear subframe. You can access all of these areas although the bulkhead crossmember is the the most difficult and will need some lateral thinking on the best approach (front footwells, tucked up under the lower dash rails there is a cutout one each side.)

 

The inner /outer sill can be accessed via the flutes in the outer sill. Be very liberal with your application here to ensure you get the best protection possible. The rear valance closeouts normally have drain holes in them so use these but make sure once done they are clear to allow any moisture to drain out. The A and B posts are best done from inside the car and may need some trim items to be removed. The floor crossmember has a few holes that can be used to pump your product into.

 

The rear subframe. this is notorious for collecting detritus so it really needs to be thoroughly cleaned. Once done liberally apply your product into every gap you can see. The front subframes are normally very easy to access and what you see is what you get. (engine oil from any leaks helps to maintain them)

 

Doors, boot lid and bonnet. The doors will need coating inside, so take off the door cards, carefully remove the plastic liner enough to get access then pump in the product. Do make sure the drain holes are kept clear. Reassemble everything ensuring the plastic membrane is fully sealed on. This is important.

 

The boot lid is easy to do when its opened. The bonnet depending on whether its a roundnose (which your car will be ) or a clubby will need some careful application into the underside bracing.

 

So for a straight fwd on the road car process, then that is pretty much it.

 

So next (yes there is more and it depends on the underside finish) The underside as it currently is. Is it painted?? is it stone chipped?? Is it covered in wax based product??

 

If its painted and i mean by painted onto metal and nothing else then the wax based products are what you need. But obviously you need to ensure there is no bare metal / damaged paint at all.

If its stone  chipped (so a mottled rough looking rubbery finish) a couple of things here to think about. If any of it is flaking at all then that affected area needs to be removed (a wire cup on a grinder will do the job) until its all solid. You can buy spray cans of stone chip to re apply to those affected areas. Apply a topcoat of paint after if has been painted. Now you can apply a light clear coat of a wax based product to all of it for extra protection.

 

If its covered in a dark / black wax based coating, this makes checking anything underneath impossible to really determine its state. But if you are happy there is nothing dubious lurking there, any areas where its missing, thinned down, just apply some more.

 

Quite a lot to think about but its in the cars best interest to make sure there is as much protection as possible. Giving the car regular washes especially underneath paying particular attention to the front inner wings right up under the scuttle corners, the rear subframe and so on.

 

Ideally when at home the car needs to be under cover if possible, but if not you can get external covers to help protect your pride and joy.

Brilliant comprehensive explanation of how to protect against corrosion, nice one!



#14 Compdoc

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Posted 15 November 2021 - 04:50 PM

I can definitely recommend Jotun Jotamastic 87 if you live near the coast.

https://www.ebay.co....tUAAOxyYANTa3jY

It's an epoxy primer that is used on the handrails and other metal parts of large (and small), ships to protect them from salt spray. It's relatively cheap, you can put it on with a roller and its as tough as old boots.
 






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