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Rust Proofing After Welding


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#1 headsock

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Posted 15 June 2012 - 05:42 AM

How do you guys rust proof the inner sections after cutting and welding the rusted sections.

Have any of you guys just cut out the rusted section and use fiberglass instead, for non-structural parts? Basically replace the sections thats rusty with fiberglass. One of the better Mini restorers near me said he does this, he says it lasts longer. Like the door skin for example. Getting a new door would be useless because it'd rust again after a year or 2. All my rust looks cosmetic, no where near what gets posted in here.

Here's my rust problem:

1. An inch or so in the pinch-welded section of the sill. It hasn't gone thru, the sill itself, just the pinch welded part.
2. Corner where wing meets cowl, an inch sized hole. Do you weld the wing and cowl together?
3. Corner below right side tail light. 3inch sized hole.
4. Whole door. Probably gona get a new one.

Edited by headsock, 15 June 2012 - 05:44 AM.


#2 mini-luke

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Posted 15 June 2012 - 07:01 AM

Don't go any where near a ''mini restorer'' who fills holes with fibreglass, it's a complete bodge. If they're one of the better ones I'd hate to see the worse ones work.

The correct thing to do is to replace the affected panel , like re-skinning the doors. If painted properly inside and waxoiled, they'll last 10+ years. The sill needs sorting properly with a welder, it's a MOT fail as the sills are structural.

#3 headsock

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Posted 15 June 2012 - 07:45 AM

How do you get waxoil inside the sill? I'm tempted to leave it as is, just treat with rust converter, but the rust might spread. But then again if I get it welded the inner part will surely rust?

The only part that's currently rusted is where the door seal clamps on to. It hasn't gone thru the metal, but looks quite thin.

#4 mayhem13

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Posted 15 June 2012 - 08:10 AM

If you not got over sills just spray up in the vents from under the car.

#5 sonikk4

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Posted 15 June 2012 - 09:33 AM

If i was you post some pictures to give us a clearer view of the afflicted areas.

Its been a common thing on here lately with regards to what do i do with rust in these areas and the answer is always the same, replace the panel or at the very least cut out the rusted area and replace with new metal.

The wing is toast i'm afraid.The rust 99% of the time starts within the seam or from behind the panel. Its impossible to eradicate the rust from the seam without major surgery plus if the rust is between the wing and the front panel seam then both items will be affected.

The rear panel area will need the section cutting out and a new piece welding in place, however it depends from where the rust has started. Again a picture tells a thousand words.

The flange you are talking about where the sill joins to the door step or the rear quarter panel can be fixed by removing that particular section and welding in a new piece. Here again though lies the rub. The rust like mentioned at the very beginning forms within the joint and spreads out. I would put money on it if you removed that piece then got a torch and mirror inside you will find more rust. It may look good from the outside but the inside WILL tell another story.

Right to the door. Unless the door is brand new straight from the packet you will be gambling on getting a door 100% rust free.They can be re skinned and repaired quite easily and will take about a day or two depending on what is behind the skin.

I always paint inside the skin before re fitting and make sure there is paint on any non welded surface within the door structure. Once the skin is on i try to force more paint into the inside of the door skin followed by copious amounts of waxoyl coating all of the internal side of the skin and door structure. DO make sure the drain holes are clear.

The sills again can have a similar process applied to them but all of the welded areas need a coat of zinc rich weldable primer sprayed on the mating faces. Again once welded and cleaned up using flexible tubing that comes with the big Waxoyl kits inject waxoyl into the sills trying to cover as much area internally as possible.

If you replace the wing or front panels or anywhere you can get to the back of a panel then i would suggest getting a good quality automotive sealant or if you are in the aerospace industry semkits with something like PR1436 or PS870. Coat all of the seams to ensure no moisture ingress happens then hopefully you should prevent any rust occurring in those areas for many years to come.

#6 headsock

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Posted 15 June 2012 - 10:07 AM

Thanks for the tips.

Will post better pics tom. (zoomed phone pics below)

Posted Image
Posted Image

#7 AVV IT

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Posted 15 June 2012 - 10:07 AM

How do you get waxoil inside the sill? u


Get a Waxoyl pressure can kit and an extension probe. Following the instructions supplied with the product, dilute the waxoyl down with white spirit so that it's thinner and will flow through the extension probe. Then feed the probe all the way inside the sills form the bottom of the rear companion bins, then spray the product whilst slowly withdrawing the probe.

Also get underneath the car and feed the probe up through each vent in the bottom of the sills and inject more of the stuff (not possible if you have oversills fitted) Later models also have a series of rubber bungs inside the car along the length of the back of the door step, which can be removed in order to spray waxoyl into the sill.

Posted Image t

Edited by AVV IT, 15 June 2012 - 10:08 AM.


#8 headsock

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Posted 15 June 2012 - 10:16 AM

Re waxoyl.

It says that water will simply be dispersed. But what about the muck thats accumulated over the years, will a pressure washer reach all the areas needed?

#9 AVV IT

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Posted 15 June 2012 - 10:28 AM

I wouldn't go near a classic mini with a pressure washer personally, as it will strip away paint and any rustproofing and force moisture into corrosion areas making them worse. :(

Any build up of dirt that has accumulated, really needs removing manually and any corroded areas beneath preparing, treating and fully repainting before applying Waxoyl to it. Apart from the areas around the vent openings the inside of the sills should be relatively clean as they're fairly well protected form the elements, corrosion tends to occur inside the sills due to a build up of condensation as opposed to dirt and rain water.

Edited by AVV IT, 15 June 2012 - 10:29 AM.


#10 mini_in_progress

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Posted 15 June 2012 - 11:04 AM

Thanks for the tips.

Will post better pics tom. (zoomed phone pics below)

Posted Image
Posted Image


mate, if thats all the rot on your mini your a very lucky man! there is nothing stopping you apply a phosporic based rust converter on there cleaning it up and filling/fiberglassing and painting them areas as a quick fix, obviously new metal would be better. i think when you said sills everyone asumed outer! thats the doorstep inner sill joint! thats covered with a rubber strip. id also stick a bit of grease in the strip to stop it going again as its where the rain runs down and gathers!

#11 headsock

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Posted 15 June 2012 - 11:48 AM

Lol yeah. After viewing the resto pics in here, was hesitant to post this.

There's a little more rust, but those have both sides accesible. That and the doors are rotten.

Anyways, decided to get them metal-worked, then if it rusts again, gona fiberglass instead.

#12 sonikk4

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Posted 15 June 2012 - 03:09 PM

The wing is a goner but again if you want a quick fix you could fill it but will very quickly rust again (washes mouth out for saying fill it :X ). Not wanting to put a downer on you but there looks like rust streaking from the top of the scuttle as well. That will need to be investigated if so.

The inner sill to door step flange could be cut out and two new sections welded in place. The other thing here with the wing is it may be hiding more rust around the lower part of the scuttle but as when you take the wing off you will be able to see what is going on.

#13 headsock

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Posted 15 June 2012 - 03:41 PM

The wing is a goner but again if you want a quick fix you could fill it but will very quickly rust againtle as well.


Goner, meaning I have to replace the wing? I was planning on a cut and weld.

The other thing here with the wing is it may be hiding more rust around the lower part of the scuttle but as when you take the wing off you will be able to see what is going on.


Hopefully it isn't bad. But after a brief inspection, the metal under the hole seems solid, some surface rust though.

#14 sonikk4

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Posted 15 June 2012 - 03:49 PM

The corner of the wing is actually a flange, ie behind what you see is a lip that should be attached to the scuttle flange.So what i mean by behind the wing is this particular area and it will be rusty it just depends on how bad. Now the hole at the top of the wing again behind that where its close to the scuttle will be part of that flange as well with possibly the same problem.

Changing tack slightly here what's the front of the wing like especially around the headlight and where it meets the front panel??? any rust?? if so it will pay you to replace the wing.

Sorry not trying to make life hard here but when a wing decides to start rotting its always going to be in places where muck collects and because the metal is really thin 0.9mm it does not take long for it to corrode.

#15 Tamworthbay

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Posted 15 June 2012 - 04:14 PM

For rustproofing Dynax S50 is light years ahead of waxoyl. You can buy it from www.bilthamber.com If you have any questions give them a ring and ask for Peter Hamber. The guy knows rust conversion/ prevention better than anyone else I know. Their stuff is brilliant - the Dynax S50 comes in a big spray can with a very long tube. I have used it on my daily draive MGB Gt for over four years and despite driving in ALL weathers there has been no degradation. Needless to say all the cavities in my mini have been coated in the stuff.

For some weird reason the original link doesn't work try this: www.bilthamber.com

Edited by Tamworthbay, 15 June 2012 - 04:18 PM.





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