Underseal

[Pob 1]

Hi all,

 

I know this has been covered in a couple of recent topics, but with conflicting information I'm getting slightly confused.

 

I've removed the rear beam to get it refurbished, so it was perfect time to deal with the surface rust on the underside of the bootfloor. I'm in the process of removing the old underseal and rust with a angle grinder (Not much fun ) I've also got a new panel to replace the left bumper mounting point on the rear wing.

 

What is the best for preventing rust when I've got it down to bare metal? I've spoken to a friend about it and he suggests Stone Guard, but I'm not so sure. I also want to protect the wheel arches, the original rust protect seems in good condition so I was thinking giving it a sand and spray with underseal. I've also been told to use Red oxidised primer, underseal then wax oil...

 

Thanks,

Dan

[Rom 0]

Dont take this as gospel, only my understanding or views

 

Red Oxide is more of a primer, id use it for repair work, weled over rust, fillers etc.

 

Waxoil is more for tubular sections, cavities etc. Inside chassis legs etc where you cant get anything else too.

 

Underseal is general purpose thick protection against damage etc. Its more to give a protective coating, to stop things being damaged / exposed and then rusting. If rust is under it, it will continue to rust.

 

Stone Chip is like underseal, but a bit less heavy duty. Often used on sills, metal valances etc before being painted over.

 

If its under the car id use underseal. Id apply it straight to the painted metal. Or Red Oxide any repairs then underseal. Arches id probably stone chip and paint over (well id use white stone chip as my cars white;) )

Then if you wanted, Waxoil inside any cavities, box sections etc.

 

Thats only what i do / would do. Im no expert !

[toddydal 1]

stone chip or underseal is fine

[Pob 1]

stone chip or underseal is fine

 

 

Thanks for the replies. The boot floor is bare metal in places, would this need priming before I underseal? Rom, you also mentioned that if there is rust it will continue to rust.... Why? I thought moisture/water is the cause of rust to form on metal without this it shouldn't spread anymore? The reason I ask is, removing all rust i.e very small pitted areas is almost impossible. I've got a rust inhibitor would this stop it spreading?

 

Thanks,

Dan

Edited May 8, 2008 by Pob

[toddydal 1]

you should never leave bare metal for very long,you should have acid etch primed it or put some kind of primer sealer on the bare bits 1srt,other wise moisture will attack the bare metal and rust quickly again

Edited May 8, 2008 by toddydal

[RossD 44]

What I have been doing in my project when finding rust, is grinding it down to bare metal, Zinc primer, follwed by several layers of paint from a rattle can, letting that harden for a week or so and then plastering it in underseal.

[Rom 0]

Rom, you also mentioned that if there is rust it will continue to rust.... Why? I thought moisture/water is the cause of rust to form on metal without this it shouldn't spread anymore?

 

In the same way painting over rust wont cure it. It will bubble back through.

 

I meant i wouldnt just apply underseal direct to rust. If its been ground back / repaired / primered or whatever then fine. I think theres a loctite rust treatmeant ive seen a few people using, including smart repair guys etc. As ive said, im no expert Im not so sure anything can eliminate rust once it has set into the metal ? Other then cutting it out and welding in fresh metal. They may help prevent it, but i dont think there is a miracle cure.

 

Maybe some of the bodywork guys will have some better answers

[toddydal 1]

i agree the only way to get shot of bad rust is cut out and replace it, if its just surface rust then you can grind it right back to nice clean bare metal and then treat it with the rust treatment,etch it, prime it and then paint

[Pob 1]

i agree the only way to get shot of bad rust is cut out and replace it, if its just surface rust then you can grind it right back to nice clean bare metal and then treat it with the rust treatment,etch it, prime it and then paint

 

Thanks for the replies. I've spent about 4-5 hrs getting the rust and underseal off with a angle grinder. I degreased the whole boot floor and applied a rust converter to all the floor as its bare metal. I'm going to paint it with Zinc primer, then a couple coats of gloss black (Possibly give it a light sand to key the surface), underseal it and finally wax oil the box sections. That should be ok shouldn't it?

 

Thanks

Dan

[toddydal 1]

yeh that should be ok,it sounds like a messy job getting all the old underseal off but when its done itl be worth it in the end

[Pob 1]

yeh that should be ok,it sounds like a messy job getting all the old underseal off but when its done itl be worth it in the end

 

I need a little more advice about rust protection. I've finished the boot floor, now moved onto the middle section. I removed the exhaust and want to clean up the middle section and deal with the small bits of surface rust. Other than the small blobs of rust the original rust protection is in good condition. What do you recommend I protect the underside with? I intend to wash, degrease and grind the small blobs of rust to bare metal. I'm thinking of using polyurethane sealant over the bits ive ground to the bare metal, and underseal it.

 

Any suggestions?

Thanks,

Dan

[DamirGTI 342]

Well i would most certainly apply some good/quality rust converter on the areas which you've cleaned of the rust , and on the bare metal surfaces also (if you buy bigger package of say 1l , cos it won't do any harm ...) , or you can use zinc/red oxide primer but use them just on the fresh metal where you've stripped the paint of , for areas previously cleaned from the rust you need rust converter if you want proper long lasting effect ..

Then you can apply a few coats of regular primer if you like or you can paint straight over the rust converter when it's finished with chemical reaction cos the rust converters are like primers , they have good paint adhesion (use some durable color , Hammerite is best me thinks or plain 1pack synthetic oil based paint , or for the faster drying cellulose/nitro paint .. apply a thick coat), also the zinc/red oxide primers are ready for painting straight on .

 

Afterwards seal repaired areas (or best , seal whole floor surface) but not with sealant , use proper underseal (rubber resin based , these products also contains various rustproofing additives ..) , apply a few coats (if you have access to the air compressor and UBS gun you can make fair better/effective job with underseal then applying it from the rattle can , and you can apply more complete and thicker coat ) ... job done .

 

Hope this helps

 

Rgs !

Damir

Edited June 3, 2008 by DamirGTI

[Pob 1]

Thanks for the reply, I've got Primer, Hammerite and Tetra Schutz that I use a compressor and underseal gun. So that should be ok? I used Zinc primer, a few coats of cellulose paint and underseal (Tetra Schutz) and wax oiled box sections and bits I could get to on the boot floor, something similar should be ok?

 

I'm looking at undersealing the whole underside, its not that bad at the moment, but there is a few spots that need attention.

 

Thanks,

Dan

 

Well i would most certainly apply some good/quality rust converter on the areas which you've cleaned of the rust , and on the bare metal surfaces also (if you buy bigger package of say 1l , cos it won't do any harm ...) , or you can use zinc/red oxide primer but use them just on the fresh metal where you've stripped the paint of , for areas previously cleaned from the rust you need rust converter if you want proper long lasting effect ..

Then you can apply a few coats of regular primer if you like or you can paint straight over the rust converter when it's finished with chemical reaction cos the rust converters are like primers , they have good paint adhesion (use some durable color , Hammerite is best me thinks or plain 1pack synthetic oil based paint , or for the faster drying cellulose/nitro paint .. apply a thick coat), also the zinc/red oxide primers are ready for painting straight on .

 

Afterwards seal repaired areas (or best , seal whole floor surface) but not with sealant , use proper underseal (rubber resin based , these products also contains various rustproofing additives ..) , apply a few coats (if you have access to the air compressor and UBS gun you can make fair better/effective job with underseal then applying it from the rattle can , and you can apply more complete and thicker coat ) ... job done .

 

Hope this helps

 

Rgs !

Damir