Waterproof Filler?.

[Keithmac]

Hello all, I'm looking for a filler that is completely waterproof.

I've seen Isopon P40 is?.

I have already bought a load of Big Boy Metal Filler, Big 21 but can't get an answer out of Silverhook if it is fully waterproof or not!.

Don't mind buying some P40 to dress the welds up if that's the best option, or is there better out there?.

Seen a few people use the P40 so seems the best bet?.

 

[ajlelectronics]

Epoxy prime it, then it is fully waterproof. Fill on top with whatever and then prime over the top.

 

[bert]

Epoxy Filler is available but mighty expensive

 

[Agroshield]

Your big boy is just standard two-part polyester filler with aluminium powder as a filler to the filler. So it is the same chemically as P38.

See post #2 here: https://www.mig-welding.co.uk/forum/threads/car-body-filler.69366/

and second post here: https://www.pistonheads.com/gassing/topic.asp?h=0&f=11&t=1471754

P40 is fibreglass (resin) based.

 

[bert]

International make epoxy filler iirc for 500g is £75

 

[Ross365]

I have already bought a load of Big Boy Metal Filler, Big 21 but can't get an answer out of Silverhook if it is fully waterproof or not!.

Absolute fact; all polymers are permeable to water, some more, some less. Water diffuses through polymers. So, how do you want to define "waterproof"? Reason I know this; worked on the development of an anti-tank weapon where there was concern about the lifetime reliability of the initiator system.

 

[Keithmac]

Thanks all, think for me P40 is the way to go then (filler wise).

Will find a use for the Big21 but can't guarantee no rain between application and top coat at the moment so it will suck water up I believe.

Come summer time when it gets a proper coat of paint I can use my fine filler up.

 

[ajlelectronics]

Will find a use for the Big21 but can't guarantee no rain between application and top coat at the moment so it will suck water up I believe.

So epoxy prime it. You can do that 15 mins after flatting the filler. Even by brush will do and will buy you as much time as you wish.

 

[Keithmac]

So epoxy prime it. You can do that 15 mins after flatting the filler. Even by brush will do and will buy you as much time as you wish.

What's best one for home winter use outdoors?. Probably mix and brush on as you say sounds easiest.

 

[ajlelectronics]

What's best one for home winter use outdoors?. Probably mix and brush on as you say sounds easiest.

For brushing, one of the Jotun products would likely be the right choice. @Dcal or @Burdekin are more knowledgable about those, I use Lechler 29107 exclusively but it isn't so brushable.

 

[Keithmac]

Thanks, will have a look further into it, much appreciated.

 

[ukracer]

So epoxy prime it. You can do that 15 mins after flatting the filler. Even by brush will do and will buy you as much time as you wish.

Is epoxy primer 2 part?

 

[ajlelectronics]

Is epoxy primer 2 part?

It is, but non isocyanate.

 

[tom2207]

Hello all, I'm looking for a filler that is completely waterproof.

I've seen Isopon P40 is?.

I have already bought a load of Big Boy Metal Filler, Big 21 but can't get an answer out of Silverhook if it is fully waterproof or not!.

Don't mind buying some P40 to dress the welds up if that's the best option, or is there better out there?.

Seen a few people use the P40 so seems the best bet?.

what exactly are you trying to achieve .... may be better to explain then others can tell you what they do ,,
just a thought.

 

[Melvyn Best]

Body solder is waterproof , don’t know if it would be good for your application?

 

[Keithmac]

I have looked at Lead Loading, looks great but also a fine art!.

I'm just looking a best way to dress and waterproof bodywork welds.

Normal filler being porous won't do the job (maybe with expoxy primer it would though).

I had seen a guy that uses P40 as a first pass on wheel arch repairs etc and he uses it as a water barrier that makes sense.

Working outdoors it's a pain, and sometimes need to go about things a different way.

I have some Lap welds to dress up, just looking at most reliable option really.

Quite disappointed at Silverhook as it was classed as external filler but what can you do..

 

[Burdekin]

Epoxy primer, filler, epoxy primer.

 

[bert]

+1 for epoxy primer, filler work then epoxy primer over the top.

If your looking to leave filler for a whilst before priming over then epoxy filler is your only option.

The marine industry uses a shed load of it

 

[tom2207]

its like painting a steel boat ,,, once a boat is painted the steel does not get wet ,,, the coatings get wet , thats what stops the rust , same on a wheel arch repair ,, the steel will rust if its not covered , so worrying about water proof fillers isnt the issue , work out how to get a protective coat on it when your not working at it , both steel and filler alike ,,, guide coat of paint or what ever ,,, then it will get sanded back at the paint stage ,,
dont overthink it.

 

[Keithmac]

its like painting a steel boat ,,, once a boat is painted the steel does not get wet ,,, the coatings get wet , thats what stops the rust , same on a wheel arch repair ,, the steel will rust if its not covered , so worrying about water proof fillers isnt the issue , work out how to get a protective coat on it when your not working at it , both steel and filler alike ,,, guide coat of paint or what ever ,,, then it will get sanded back at the paint stage ,,
dont overthink it.

I've been using weld though Zinc Primer so far (which isn't ideal), just don't like the idea of having porous filler but as you say probably overthinking it.

Jotun 87 seems to be the way forward, will be brushing it on for time being.