DIY solution to stop roof corrosion

[Edsr]

I've read a few threads on this, and other than using some tape (a solution I don't quite understand the physics of), I wondered if anyone had tried gluing the seal on using automotive/RV sealant (the black stuff that comes in a metal tube for a caulking gun), using masking tape 5mm above the seal all round the roof and caulking the gap between the tape and the seal to create a watertight fillet that prevents water getting into the U channel? When removed, the masking tape will leave a clean edge that looks like an extension of the seal, bonded to the roof - how you'd seal a bath tub but using that black stuff that bonds like the proverbial to a blanket.

On a similar point, my roof is pretty good (compared to some horror stories on this forum, and considering it's 10 yrs old), but the 'deflector' that sits in front of the pop roof, is bubbling along the top of the windscreen in one corner - 1.5" diameter or thereabouts. Apparently this is now resolved on newer models (though the roof seal issue remains) - can anyone tell me what they did to change the design? I ask so that I can brief a suitable bodyshop on how to mimic a factory design change when it gets repaired.

(and finally - rant - looking out of the upstairs window of my house, I can see they designed a series of long thin puddles into the roof, perhaps to make it prone to collecting algae in the hardest to reach place possible; why anyone thought concave was better than convex for those moldings beggars belief)

 

[WelshGas]

I've read a few threads on this, and other than using some tape (a solution I don't quite understand the physics of), I wondered if anyone had tried gluing the seal on using automotive/RV sealant (the black stuff that comes in a metal tube for a caulking gun), using masking tape 5mm above the seal all round the roof and caulking the gap between the tape and the seal to create a watertight fillet that prevents water getting into the U channel? When removed, the masking tape will leave a clean edge that looks like an extension of the seal, bonded to the roof - how you'd seal a bath tub but using that black stuff that bonds like the proverbial to a blanket.

On a similar point, my roof is pretty good (compared to some horror stories on this forum, and considering it's 10 yrs old), but the 'deflector' that sits in front of the pop roof, is bubbling along the top of the windscreen in one corner - 1.5" diameter or thereabouts. Apparently this is now resolved on newer models (though the roof seal issue remains) - can anyone tell me what they did to change the design? I ask so that I can brief a suitable bodyshop on how to mimic a factory design change when it gets repaired.

(and finally - rant - looking out of the upstairs window of my house, I can see they designed a series of long thin puddles into the roof, perhaps to make it prone to collecting algae in the hardest to reach place possible; why anyone thought concave was better than convex for those moldings beggars belief)

Windscreen Panel - VW changed the Alloy mix from MY 2015 onwards.
Elevating Roof edge - Your suggestion could work but the idea of the tape is to keep the steel insert insulated from the aluminium of the roof.
Convex or Concave you'll still end up with channels but this is for strengthening of the roof so it doesn't buckle when lifted while keeping the weight down.

 

[yossarian]

... a solution I don't quite understand the physics of...

The two metals, if electrically bonded, will cause galvanic corrosion. https://en.wikipedia.org/wiki/Galva...led bimetallic,the presence of an electrolyte.

 

[Perfectos]

Edsr,

The tape to “fix“ the problem can be bought and applied easily.
lots of threads on the forum about this specific issue.
it creates a barrier to prevent to steel reinforcing in the rubber seal from making contact with the aluminium roof. It’s a low tech solution to a real problem .

you can inspect your existing roof seal, removing a small section at a time, cleaning the roof edge and rubber seal as you go, inspecting the roof where the rubber seal touches it. If the rubber seal shows any sign of rust, replace the whole roof seal ASAP. small spots of corrosion can be treated by before applying the remedial tape to the roof edges.

MY18 rubber seal was showing signs of rust less than a year old ! It’s not just old seals that rust.

Bonding the seal to the roof will not prevent the galvanic reaction it will just prevent the roof rubber from being removed it it ever needs replacing.

some Reading would be a good starting point for this highly discussed subject. The remedial tape is shown in some.

 

[sidepod]

Apologies if this has been covered before but is it not a case of replacing the seal with one that doesn’t contain a steel reinforcement? There are a million rubber channel sections available?

 

[ArunAlec]

Windscreen Panel - VW changed the Alloy mix from MY 2015 onwards.
Elevating Roof edge - Your suggestion could work but the idea of the tape is to keep the steel insert insulated from the aluminium of the roof.
Convex or Concave you'll still end up with channels but this is for strengthening of the roof so it doesn't buckle when lifted while keeping the weight down.

Re the convex/concave.....
If the concave channels on the roof were changed to be convex. So they were higher than the roof rather than concave and forming channels then there would be nowhere for water to puddle.

I do accept that the current design probably offers more rigidity due to the curvature of the roof and the concave channel.

 

[Louis II]

My van went in recently and as part of the repair the seal is now bonded as you describe.
It makes a lot of sense to me as it prevents both water ingress and any movement of the seal that could wear away the paint and expose bare aluminium.
Without the water as an electrolyte and with the paint preventing electrical contact between aluminium and steel the corrosion shouldn’t happen.
If the seal can still move the tape is just a sacrificial layer that will eventually wear out, the paint is next and water can still get behind the seal and create an electrical contact between the seal and aluminium roof.

 

[Louis II]

Apologies if this has been covered before but is it not a case of replacing the seal with one that doesn’t contain a steel reinforcement? There are a million rubber channel sections available?

That would stop galvanic corrosion but if the seal can still move and with a lovely mixture of water grit and in winter a bit of salt for good measure trapped behind / in the seal I think the paint is still likely to get damaged exposing bare aluminium that will corrode even without the presence of a steel band.

 

[sidepod]

So every once in a while remove the seal and clean/apply a smear of waterproof grease. We’re not splitting the atom here.

 

[steve_b]

Apologies if this has been covered before but is it not a case of replacing the seal with one that doesn’t contain a steel reinforcement? There are a million rubber channel sections available?

You would think that if it were that simple then VW would just change it and save them millions. However the same could be said for many other bits of bad design (sliding windows...).

Any idea why the strip is reinforced? Is it maybe a single piece loop and the steel holds it to a dimension? I would be interested in any possible equivalents that could be found.

Surely the might of VW can source a Kevlar replacement. Simple fixes are always the best...

 

[WelshGas]

You would think that if it were that simple then VW would just change it and save them millions. However the same could be said for many other bits of bad design (sliding windows...).

Any idea why the strip is reinforced? Is it maybe a single piece loop and the steel holds it to a dimension? I would be interested in any possible equivalents that could be found.

Surely the might of VW can source a Kevlar replacement. Simple fixes are always the best...

I think it is probably related to the amount of force applied to the seal when opening the roof. It can stick quit well to the bodywork due to the actions of the weather, dirt and tree sap unless constantly cleaned and lubricated. After almost 20 yrs of using the same system I'm sure VW would have examined alternatives if it was cost effective.

 

[ArunAlec]

You would think that if it were that simple then VW would just change it and save them millions. However the same could be said for many other bits of bad design (sliding windows...).

Any idea why the strip is reinforced? Is it maybe a single piece loop and the steel holds it to a dimension? I would be interested in any possible equivalents that could be found.

Surely the might of VW can source a Kevlar replacement. Simple fixes are always the best...

I assume that the “reinforcement“ is purely to act as a means of gripping the rubber seal to the roof in the same way as door seals. I would have thought an alternative would be a bonded seal. Even no seal on the lifting section but a bonded seal fixed to the static roof for the top to close down onto.

 

[Ozzy Pete]

VW MUST have known when they designed the roof that galvanic corrosion would at some time rear it’s ugly head. It’s not a secret that Aluminium +steel+water is not a good combination. A simple design change of the roof seal would have prevented this problem, or maybe bonding the roof seal so that water couldn’t get in. I had the repair done by VW about two and a half years ago and this time they actually bonded the seal on completely so you can’t Take it off at all. I’ve heard of all different methods of rectify the corrosion
From tape to bonding, but I do know that Two and a half years later I can’t see any corrosion creeping “Above” the seal so I take it the repair worked.

 

[Perfectos]

for completeness of this thread, relating to the OP question Regarding the tape & how to brief a third party.

Here is a thread from @Loz , fitting of the factory “fix”

Adding the 3M tape to roof edges

I checked my roof last summer at 1 year old and all was good. Earlier this year I ordered the 3M protection tape to do the edges myself before the corrosion starts but today was the first Hot day I got to fit the tape. So I removed the side and rear parts of the roof seal and used some detailer...

vwcaliforniaclub.com

 

[Edsr]

Thanks for the advice and info here.

I do like the idea of @ArunAlec - no seal on the pop roof, instead have one it drops down onto.

I think I now understand why the metal reinforcement is an issue as that roof is *really* tightly shut so I can see how the sharp edge of the roof would cut through the rubber and down to the metal clips over time as WelshGas suggests.

Just so I'm clear - the 3M tape - this is to basically act like heavy duty electrical insulation tape - it stops the flow of electrons through the water sitting between the two metals? Presumably the thickness of the tape helps prevent the alu sheet cutting thru it and back into the same metal clips in the seal?

I think @Ozzy Pete has answered my question though - that's what I was thinking; eliminate the water = no electrolysis. I wonder if anyone has had this fix for a longer period as perhaps 2 years is still a little early.

I think when I replace my seal I will bond it, and use the tape.

As with the convex comments, if they were convex, the roof would definitely drain properly but presumably it's marginally stronger with concave indents.

@WelshGas - ref changing the alloy in the windscreen panel - does this mean the fix for the corrosion on mine is to buy a new one and get a bodyshop to fit it?

 

[WelshGas]

Thanks for the advice and info here.

I do like the idea of @ArunAlec - no seal on the pop roof, instead have one it drops down onto.

I think I now understand why the metal reinforcement is an issue as that roof is *really* tightly shut so I can see how the sharp edge of the roof would cut through the rubber and down to the metal clips over time as WelshGas suggests.

Just so I'm clear - the 3M tape - this is to basically act like heavy duty electrical insulation tape - it stops the flow of electrons through the water sitting between the two metals? Presumably the thickness of the tape helps prevent the alu sheet cutting thru it and back into the same metal clips in the seal?

I think @Ozzy Pete has answered my question though - that's what I was thinking; eliminate the water = no electrolysis. I wonder if anyone has had this fix for a longer period as perhaps 2 years is still a little early.

I think when I replace my seal I will bond it, and use the tape.

As with the convex comments, if they were convex, the roof would definitely drain properly but presumably it's marginally stronger with concave indents.

@WelshGas - ref changing the alloy in the windscreen panel - does this mean the fix for the corrosion on mine is to buy a new one and get a bodyshop to fit it?

The last estimate I saw for the repair included replacing that panel was circa £4000. It is not just the panel above the windscreen but extends halfway down the length of the vehicle - all 1 moulding.

The new VW repair involves cutting the panel away above the windscreen and fitting a plastic colour coded cap - lots of problems have been experienced with this.

The method I would favour is finding a good, experienced independent body shop that specialises in classic cars, Land Rovers ( which suffer the same problem) etc:, not your typical Insurance accident repairs and get the corrosion areas treated, a zinc rich primer and respray - a Forum member paid circa £400+ for this in Scotland. If the original took 10yrs to appear then £500 every 5-10 yrs would be much more cost effective.

 

[B J G]

The last estimate I saw for the repair included replacing that panel was circa £4000. It is not just the panel above the windscreen but extends halfway down the length of the vehicle - all 1 moulding.

The new VW repair involves cutting the panel away above the windscreen and fitting a plastic colour coded cap - lots of problems have been experienced with this.

The method I would favour is finding a good, experienced independent body shop that specialises in classic cars, Land Rovers ( which suffer the same problem) etc:, not your typical Insurance accident repairs and get the corrosion areas treated, a zinc rich primer and respray - a Forum member paid circa £400+ for this in Scotland. If the original took 10yrs to appear then £500 every 5-10 yrs would be much more cost effective.

Commercial vehicle Body Painters will also have the knowhow and paint materials required. Many commercial vehicles have Alloy bodies fitted which undergo extreme environmental conditions.

 

[lfm]

I was informed, on Wednesday, that there is a recall for this (probably the tape solution), when my 2010 Cali was being serviced. They didn’t need to do anything on mine due to previous repair but the fact they were willing to, on an 11 yr old van suggests you should check with your friendly dealer.

 

[WelshGas]

I was informed, on Wednesday, that there is a recall for this (probably the tape solution), when my 2010 Cali was being serviced. They didn’t need to do anything on mine due to previous repair but the fact they were willing to, on an 11 yr old van suggests you should check with your friendly dealer.

The Tape on Elevating Roof recall is for all Californias from 2010 to approximately 2019.

 

[Blue Yonder]

So every once in a while remove the seal and clean/apply a smear of waterproof grease. We’re not splitting the atom here

Agree the best grease to use for this application would be Johnson/Evinrude Triple Guard Grease, which has the following properties

• Formulated higher water resistance and improved adhesion to metal
• Will not swell seals, packing or o-rings
• Compatible with other greases
• Totally waterproof to prevent water wash-off - will not wash away under normal marine application
• Repels water - will not mix with water and lose lubrication quality
• Prevents corrosion by forming a protective layer - even in saltwater
• Maintains stability - will not breakdown or lose consistency
• Not for use in wheel bearings or universal joints

 

[lfm]

Just be careful. The steel teeth in the seal can take paint off every time you move it, hence the reason for the “new” tape and the cause of the original problem. Also, as the teeth go through the grease you will end up with the same electrochemical sacrificial corrosion due to steel on aluminium. It’s not technically the water causing an issue - although that certainly speeds it up.

 

[Blue Yonder]

Just be careful. The steel teeth in the seal can take paint off every time you move it, hence the reason for the “new” tape and the cause of the original problem. Also, as the teeth go through the grease you will end up with the same electrochemical sacrificial corrosion due to steel on aluminium. It’s not technically the water causing an issue - although that certainly speeds it up.

i noted that my MY 2018 California has had the tape fitted from new. There is however there is no tape on the front edge. If you try and apply 3M protective tape (Helicopter Tape) to this edge then the front seal will not fit properly. Probably why VW omit the tape fix on this part of the seal?

i understand where your coming from with regards to your comment and it is welcomed. My view having removed the seal to inspect and clean is that water does accumulate inside the seal. Thus applying Triple Guard grease will help as is will stop the ingress of water into the seal. Note there are no steel barbs inside the seal griping the roof edge. The steel is inside the rubber seal acting as a spring to help the rubber grip the edge of the seal. However the rubber is micro porous and in the presence of trapped water inside the seal it will diffuse through the rubber causing it to corrode swell and break through the inside seal surface. It is at this point potential for it to come into contact with the aluminium and galvanic oxidation of the less noble aluminium alloy to begin. Also trapped salty water in the seal could cause the aluminium alloy roof to oxidised too. It only takes a small flaw in the protect paint for it to take hold. Applying such grease I agree is not a simple answer to the potential problem but a belt a braces approach. Note Triple Guard grease is designed for such applications it is not a bearing grease.