Discussion regarding T6 ONLY roof corrosion

[GrannyJen]

JW, this is a truly difficult subject, and for Snowy55 and others who have had endless problems with the roof corrosion issue, it must be devastating. I can't imagine how they must all be feeling right now, and I am in no way attempting to diminish their angst with this post.

However, for me, like you, I have been waiting months for my Cali to arrive, and am beyond excited about collecting it next week I have spent all those months dreaming, planning and anticipating the lifetime of memories I know this vehicle will give to me and mine.

Is the corrosion issue acceptable? No. Have VW behaved correctly and fairly to their customers? No. Will they in the future? Probably not. Am I worried about my Cali? Yes, mildly. Will it stop me buying it? Hell NO.

If I were to cancel my order tomorrow, I can absolutely guarantee on my children's lives that within 48hrs someone else will have the keys to the dream machine that I have saved for and waited for all these years. They will be in happy land and I will be as miserable as sin, as will be my kids.

This corrosion issue won’t be going away anytime soon. But, I’m an optimist. It’s a brand new vehicle. Its under warranty. I will have a chat with my dealer about it next week, let him know that I know. It won’t stop me driving it, loving it, living in it, having endless adventures in it.

It's a Campervan. Within a week the kids will have scratched the paintwork with their school bags and the idiot in Tesco’s car park will have dinged the door, and yes, I will be upset, very upset I’m sure (!) but, every time I drive it, it will make me smile.

Granny Jen is right, these are truly awesome vehicles. Don’t cancel your order, live the dream

Wonderful post.

Live the dream, to hell with the nightmare that may just never happen anyway

 

[2into1]

Out of interest, exactly how many of you worried people will take action and find a replacement seal strip without a metal insert?

Valid question, but I think the greatest barrier to doing that is the belief that if it was that easy, then surely VW would have done it ?
If it isn't the metal in the seal, could it be near enough to the metal monocoque to cause the electrolytic action?

 

[sidepod]

Valid question, but I think the greatest barrier to doing that is the belief that if it was that easy, then surely VW would have done it ?
If it isn't the metal in the seal, could it be near enough to the metal monocoque to cause the electrolytic action?

Good point. Is that section of roof not aluminium?

If this really is the cause then somebody needs to get a private consultant materials expect to take a look at the configuration of the roof and advise.

If a suitable replacement seal can't be sourced then a quote could be obtained for a bulk purchase of a bespoke seal. It could then be sold through the forum shop.

 

[Grey one]

Is there any correlation between Cali Colours/finishes and the blistering?

Who knows! VWCS may know but will they tell? The forum is great in that we can communicate but it's so difficult to pull it all together. From a personal perspective I will go ahead with my purchase as, IMO, the advantages outweigh the disadvantages.

 

[Borris]

We emailed the dealer Sunday afternoon, and by 12.30 today we had agreed that they come and collect it tomorrow (Tuesday) at 10.30 with a full refund.

I am so sorry that you have had to take this action. It is so sad. I suppose this means that you will be leaving the club?

As this problem has been going on for years, why on earth haven't VW re-thought the whole roof top panel. Instead of the main roof panel being alluminium, why not a high quality plastic molding or fibre glass replacement for the current problematic alluminium top panel. How much extra weight would a steel roof panel add and could this extra weight be saved elsewhere. Am I missing sometihing?
Given the hassle this has caused VW but more importantly their cutomers, us Cali owners, I would have thought that developing a replacement top would have been a cost effective priority.

 

[Jabberwocky]

Good point. Is that section of roof not aluminium?

If this really is the cause then somebody needs to get a private consultant materials expect to take a look at the configuration of the roof and advise.

If a suitable replacement seal can't be sourced then a quote could be obtained for a bulk purchase of a bespoke seal. It could then be sold through the forum shop.

Is the problem the struts connecting the roof to the steel body?? How well are they insulated from each other? I think this was mentioned earlier.

 

[Cali4nia-Dream]

Having just nicely taken ownership of a T6 Cali this does cause me concern.
In the past I worked as for a large pipeline company in their Corrosion Control section, it is nearly 20 years since, but the basics of galvanic corrosion haven’t changed.

Referring back to MattBWs comment “Most vehicles that have aluminium bodies use a sacrificial anode (or cathode) to prevent this. VW for some reason haven't...”

To find a material that will corrode in preference to aluminium you would have to use something like magnesium or calcium, the latter not really being suitable for other reasons, you also have to find a location where the sacrificial anode can be placed and happily corrode and protect the structure it is protecting. Fine for ships where you can bolt large lumps of magnesium on the hull and an electric current can flow through the sea water (electrolyte) to protect all the structure. Or through the ground (electrolyte) to protect buried steel work.
With a Cali roof it is difficult to maintain the structure in the electrolyte so the Cathodic protection would work is a bit of a non starter.

Referring to Snowy55s comments about the high zinc content primer. - Were the garage trying to suggest this would protect the roof?
I hope not because Zinc is often used in primers for steel, to protect a bit like old fashioned galvanising, unfortunately when you study the electric potentials of metals, often measured against a Cu/CuSO4 half cell, you have the figures Iron&steel +0.44Volts, Zinc +0.76 Volts, Aluminium +1.30 Volts, and Magnesium +1.87 Volts. You use a metal with a higher voltage to protect one with a lower voltage, so the Aluminium would be trying to protect any zinc in the paint.

It should also be noted that bending and shaping of metals can cause minute differences in the electrical properties of the metal leading to localised corrosion.

I feel from the information I have read so far there is an issue with moisture getting trapped and leading to small cells for possible corrosion. This is possibly aggravated by the steel in the rubber seal, but not necessarily.
Because of this there is no guarantee that replacing the seal with a metal free one would cause the problem to go away.

Could the problem be designed out by any other method? possibly but at the moment the only option I can think of would be a Fibreglass or Carbon Fibre roof.

Is that a feasible option - I don’t know, but I suspect probably not as I don’t know how well they would cope if the Cali got rolled, (can’t remember whose photos showed their poorly Cali).
That then leaves the other option a steel roof, which may be OK for those of us with a powered roof but it may well be too heavy for those with a manual roof.

It is a very frustrating situation.

Would I change from a T6 Cali because of this NO, in my opinion the T6 Cali beats all competitors

Sorry about the science lesson

 

[Cali4nia-Dream]

Is the problem the struts connecting the roof to the steel body?? How well are they insulated from each other? I think this was mentioned earlier.

It may not be the struts, even just the earth return wire from the roof LEDs could cause a problem.

 

[Jabberwocky]

Having just nicely taken ownership of a T6 Cali this does cause me concern.
In the past I worked as for a large pipeline company in their Corrosion Control section, it is nearly 20 years since, but the basics of galvanic corrosion haven’t changed.

Referring back to MattBWs comment “Most vehicles that have aluminium bodies use a sacrificial anode (or cathode) to prevent this. VW for some reason haven't...”

To find a material that will corrode in preference to aluminium you would have to use something like magnesium or calcium, the latter not really being suitable for other reasons, you also have to find a location where the sacrificial anode can be placed and happily corrode and protect the structure it is protecting. Fine for ships where you can bolt large lumps of magnesium on the hull and an electric current can flow through the sea water (electrolyte) to protect all the structure. Or through the ground (electrolyte) to protect buried steel work.
With a Cali roof it is difficult to maintain the structure in the electrolyte so the Cathodic protection would work is a bit of a non starter.

Referring to Snowy55s comments about the high zinc content primer. - Were the garage trying to suggest this would protect the roof?
I hope not because Zinc is often used in primers for steel, to protect a bit like old fashioned galvanising, unfortunately when you study the electric potentials of metals, often measured against a Cu/CuSO4 half cell, you have the figures Iron&steel +0.44Volts, Zinc +0.76 Volts, Aluminium +1.30 Volts, and Magnesium +1.87 Volts. You use a metal with a higher voltage to protect one with a lower voltage, so the Aluminium would be trying to protect any zinc in the paint.

It should also be noted that bending and shaping of metals can cause minute differences in the electrical properties of the metal leading to localised corrosion.

I feel from the information I have read so far there is an issue with moisture getting trapped and leading to small cells for possible corrosion. This is possibly aggravated by the steel in the rubber seal, but not necessarily.
Because of this there is no guarantee that replacing the seal with a metal free one would cause the problem to go away.

Could the problem be designed out by any other method? possibly but at the moment the only option I can think of would be a Fibreglass or Carbon Fibre roof.

Is that a feasible option - I don’t know, but I suspect probably not as I don’t know how well they would cope if the Cali got rolled, (can’t remember whose photos showed their poorly Cali).
That then leaves the other option a steel roof, which may be OK for those of us with a powered roof but it may well be too heavy for those with a manual roof.

It is a very frustrating situation.

Would I change from a T6 Cali because of this NO, in my opinion the T6 Cali beats all competitors

Sorry about the science lesson

Excellent! I really do like to understand. Thank you.

 

[Jabberwocky]

It may not be the struts, even just the earth return wire from the roof LEDs could cause a problem.

Wow! VW really do need to do some work to sort this out. Must be possible.

 

[Grey one]

Having just nicely taken ownership of a T6 Cali this does cause me concern.
In the past I worked as for a large pipeline company in their Corrosion Control section, it is nearly 20 years since, but the basics of galvanic corrosion haven’t changed.

Referring back to MattBWs comment “Most vehicles that have aluminium bodies use a sacrificial anode (or cathode) to prevent this. VW for some reason haven't...”

To find a material that will corrode in preference to aluminium you would have to use something like magnesium or calcium, the latter not really being suitable for other reasons, you also have to find a location where the sacrificial anode can be placed and happily corrode and protect the structure it is protecting. Fine for ships where you can bolt large lumps of magnesium on the hull and an electric current can flow through the sea water (electrolyte) to protect all the structure. Or through the ground (electrolyte) to protect buried steel work.
With a Cali roof it is difficult to maintain the structure in the electrolyte so the Cathodic protection would work is a bit of a non starter.

Referring to Snowy55s comments about the high zinc content primer. - Were the garage trying to suggest this would protect the roof?
I hope not because Zinc is often used in primers for steel, to protect a bit like old fashioned galvanising, unfortunately when you study the electric potentials of metals, often measured against a Cu/CuSO4 half cell, you have the figures Iron&steel +0.44Volts, Zinc +0.76 Volts, Aluminium +1.30 Volts, and Magnesium +1.87 Volts. You use a metal with a higher voltage to protect one with a lower voltage, so the Aluminium would be trying to protect any zinc in the paint.

It should also be noted that bending and shaping of metals can cause minute differences in the electrical properties of the metal leading to localised corrosion.

I feel from the information I have read so far there is an issue with moisture getting trapped and leading to small cells for possible corrosion. This is possibly aggravated by the steel in the rubber seal, but not necessarily.
Because of this there is no guarantee that replacing the seal with a metal free one would cause the problem to go away.

Could the problem be designed out by any other method? possibly but at the moment the only option I can think of would be a Fibreglass or Carbon Fibre roof.

Is that a feasible option - I don’t know, but I suspect probably not as I don’t know how well they would cope if the Cali got rolled, (can’t remember whose photos showed their poorly Cali).
That then leaves the other option a steel roof, which may be OK for those of us with a powered roof but it may well be too heavy for those with a manual roof.

It is a very frustrating situation.

Would I change from a T6 Cali because of this NO, in my opinion the T6 Cali beats all competitors

Sorry about the science lesson

Thank you for taking the time to think about this.

 

[Borris]

Having just nicely taken ownership of a T6 Cali this does cause me concern.
In the past I worked as for a large pipeline company in their Corrosion Control section, it is nearly 20 years since, but the basics of galvanic corrosion haven’t changed.

Referring back to MattBWs comment “Most vehicles that have aluminium bodies use a sacrificial anode (or cathode) to prevent this. VW for some reason haven't...”

To find a material that will corrode in preference to aluminium you would have to use something like magnesium or calcium, the latter not really being suitable for other reasons, you also have to find a location where the sacrificial anode can be placed and happily corrode and protect the structure it is protecting. Fine for ships where you can bolt large lumps of magnesium on the hull and an electric current can flow through the sea water (electrolyte) to protect all the structure. Or through the ground (electrolyte) to protect buried steel work.
With a Cali roof it is difficult to maintain the structure in the electrolyte so the Cathodic protection would work is a bit of a non starter.

Referring to Snowy55s comments about the high zinc content primer. - Were the garage trying to suggest this would protect the roof?
I hope not because Zinc is often used in primers for steel, to protect a bit like old fashioned galvanising, unfortunately when you study the electric potentials of metals, often measured against a Cu/CuSO4 half cell, you have the figures Iron&steel +0.44Volts, Zinc +0.76 Volts, Aluminium +1.30 Volts, and Magnesium +1.87 Volts. You use a metal with a higher voltage to protect one with a lower voltage, so the Aluminium would be trying to protect any zinc in the paint.

It should also be noted that bending and shaping of metals can cause minute differences in the electrical properties of the metal leading to localised corrosion.

I feel from the information I have read so far there is an issue with moisture getting trapped and leading to small cells for possible corrosion. This is possibly aggravated by the steel in the rubber seal, but not necessarily.
Because of this there is no guarantee that replacing the seal with a metal free one would cause the problem to go away.

Could the problem be designed out by any other method? possibly but at the moment the only option I can think of would be a Fibreglass or Carbon Fibre roof.

Is that a feasible option - I don’t know, but I suspect probably not as I don’t know how well they would cope if the Cali got rolled, (can’t remember whose photos showed their poorly Cali).
That then leaves the other option a steel roof, which may be OK for those of us with a powered roof but it may well be too heavy for those with a manual roof.

It is a very frustrating situation.

Would I change from a T6 Cali because of this NO, in my opinion the T6 Cali beats all competitors

Sorry about the science lesson

Thanks for your very interesting explanation. I too had heard that a zinc coating was being used to try to cure this issue. Can anyone confirm this?

 

[sidepod]

I like the idea of a carbon composite roof.
I personally don't think the aluminium roof is to provide any rollover protection.

The roof unit is such a basic bit of kit with respect to composite design it would be cheap and simple to manufacture.

There are countless companies out there capable, it just comes down to demand.

 

[Digger]

I like the idea of a carbon composite roof.
I personally don't think the aluminium roof is to provide any rollover protection.

The roof unit is such a basic bit of kit with respect to composite design it would be cheap and simple to manufacture.

There are countless companies out there capable, it just comes down to demand.

Agree. As the roof buckles easily it cannot give protection or structural strength. The frame around the aperture is the strength. Would be interesting to cost carbon replacement if anyone knows a manufacturer.

 

[Hotel California]

The main reason causing the corrosion on the edges of the elevating section is the moist and sand/dirt collecting in the rubber mostley on the back side of the roof. Roof up means water searching the lowest point thru the rubber taking dirt/sand to the lowest point at the rear of the Cali.
Than scrubbing thru the paint layer until water goes under the paint resulting in a reaction ....
There is no metal from inside the rubber seal coming out touching the alu roof , that would also be shown in rust and thats not seen when pulling of the rubber
The same in front on the front spoiler.
The plasic end caps on the brandruprail are touching the paint , friction damaging the paintlayer , water ingress between paint and alu body....reaction.

Diffrent rubber = no solution
Diffrent paint = no solution
Call VW dealer = no use , they can't fix it permanently , it will accure on any Cali .
When repaired it will stick it's head back up
The hard reality , this is not a new thing been going on years now and still no change, that says it all!

 

[RichardP]

I think the cost of a CF roof would be astronomic, it's a very large single piece. I doubt there are too many autoclave sin the world that could handle a piece that big. Cost will be several thousand at least, probably over 10.

Steel would be too heavy, the Calli is already pushing the unladen weight limit so you can't order some options with others.

Other manufacturers use Aluminium panels without problems. My daily driver car has an aluminium bonnet and doors, it's about 18 months younger than the Calli, but no sign of corrosion.

The problem must be a combination of the lack of correct isolation, the type of paint/primer and the exact Aluminium allot used. Those will all come down to money. The earliest this problem will be fixed is when the Calli is totally redesigned, anything based on the current design is going to suffer the same issues.

 

[sidepod]

The main reason causing the corrosion on the edges of the elevating section is the moist and sand/dirt collecting in the rubber mostley on the back side of the roof. Roof up means water searching the lowest point thru the rubber taking dirt/sand to the lowest point at the rear of the Cali.
Than scrubbing thru the paint layer until water goes under the paint resulting in a reaction ....
There is no metal from inside the rubber seal coming out touching the alu roof , that would also be shown in rust and thats not seen when pulling of the rubber
The same in front on the front spoiler.
The plasic end caps on the brandruprail are touching the paint , friction damaging the paintlayer , water ingress between paint and alu body....reaction.

Diffrent rubber = no solution
Diffrent paint = no solution
Call VW dealer = no use , they can't fix it permanently , it will accure on any Cali .
When repaired it will stick it's head back up
The hard reality , this is not a new thing been going on years now and still no change, that says it all!

A bead of sealant run around between the roof surface and the lip of the rubber seal to keep out said moisture/dirt. Done

 

[sidepod]

I doubt there are too many autoclavesi n the world that could handle a piece that big.

Walked past a couple on the way to my office this morning! There are plenty around.
Cost would be high but not for VW.
I would love to understand the design philosophy for that roof system, electrics and all.

 

[Alibee]

I think the cost of a CF roof would be astronomic, it's a very large single piece. I doubt there are too many autoclave sin the world that could handle a piece that big. Cost will be several thousand at least, probably over 10.

A 5mm CF sheet of the same dimensions is c.£3k retail, so <£2k to a manufacturer, and I'm sure a manufacturer of VW's size could refine the design to bring costs down a long way from that. Repairs to the alloy versions must be costing them in excess of this figure so the economics are not as bonkers as they might first seem. And an autoclave is not required, the airline industry uses other methods to achieve the same quality:

https://en.wikipedia.org/wiki/Out_of_autoclave_composite_manufacturing

 

[Ambler]

This is interesting re. the cause of rust under the seal on the elevating roof.
Our March 14 vehicle was repaired in Aug 14 after quickly showing the signs.
It was done at the nearby paint shop used by the local VW agent.
I spoke to the paint shop owner, a man with many years experience.
After making it clear he did not really want to do this but had no choice given how much business he received from VW, he said in his opinion the major factor was moisture underneath the rubber seal combined with inadequate priming of the aluminium. As to the steel strip in the rubber, he put insulation tape around the edge in case this was also a contributing factor.
I did put forward this information on here but was firmly shot down by one of our more frequent posters who felt his Landrover experience conclusively identified the cause as bi-metallic corrosion.
Of course it might turn out to be all 3.
Last time I checked no rust had returned but on the next dry day I will have another look.
I'm not holding my breath for VW to identify and publish the actual cause.

Can I also say, based on15 years of Mercedes ownership, don't expect them to be any better than VW if a problem like this occurs in the Marco Polo. With problems like this, at least on normal passenger vehicles, Mercedes tend to design them out when the vehicle receives its mid-term facelift, but do the usual stalling in the interim.

 

[sidepod]

Is this restricted to people who leave their Cali outside 365?

 

[Ambler]

Well ours stays outside, but from March - July 2014 (when I first spotted the rust) is not a long time.

 

[larrylamb]

The main reason causing the corrosion on the edges of the elevating section is the moist and sand/dirt collecting in the rubber mostley on the back side of the roof. Roof up means water searching the lowest point thru the rubber taking dirt/sand to the lowest point at the rear of the Cali.

Even on an 8 month old T6??

 

[kaf2546]

http://www.which.co.uk/consumer-rights/regulation/consumer-rights-act

Is the T6 seal/roof edge corrosion bi-metal but a different type of bi-metal corrosion to the early T5's? Maybe VW sorted the main problem but forgot the potential edge trim issue. I have a late T5 with no sign of corrosion but I wasn't of a mind to start removing seals. I remember it was a common area of corrosion behind seals on wheel arches on some cars. If it is just the edge and a different type of seal is required it might not be a huge problem to sort...

 

[snowy55]

http://www.which.co.uk/consumer-rights/regulation/consumer-rights-act

Is the T6 seal/roof edge corrosion bi-metal but a different type of bi-metal corrosion to the early T5's? Maybe VW sorted the main problem but forgot the potential edge trim issue. I have a late T5 with no sign of corrosion but I wasn't of a mind to start removing seals. I remember it was a common area of corrosion behind seals on wheel arches on some cars. If it is just the edge and a different type of seal is required it might not be a huge problem to sort...

If you haven't removed the seal how do you know you haven't got corrosion?
You won't find out until you pull a section off!!!