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more on corrosion

Yahoo Message Number: 14187
George and Egon,

The outside paint bubbles are only the visible part of the equation. It's a bit messy, but, have a look at the internal frame of the door. The original cause was the skin on the door was made from aluminum and the frame, such as it is, was steel. Add just a bit of moisture to the recipe and with the assistance of a few stray electrons runnning about from all of the installed components on the coach, the two dis-similar metals commence to behaving like a battery and the aluminum digests....corrodes at or near the contact points of the two metals. The lower part of the door will appear first thanks to the weight of the condensed moisture.
The first door fix was a door that had plastic insulators between the skin and the frame; this was the new and improoved door. I suspect that the problem with this fix was the adhesive because after some time the little gaskets slid away...bingo, corrision began anew.

I noticed this corrsion shortly after delivery of the coach and when it was returned to the dealer for repairs, his crack body shop team ground out the defects and covered the defect with body putty...sanded and painted. Sadly, that repair fell off, literally before I pulled the coach off the lot! The replacement door saga began.

CC now has a fix for this problem which is a plastic skin vice the aluminum.

I have convinced CC (actually NRVH) that it would be in everyones best interest to make this repair. With regard to covering the defect, either with stainless or a decal of some fashion, I really feel that will not last. Glue on the stainless, it will fall off.
Screw it on or rivit it on and it will corrode at the contacts.
My marine experience from keeping larger boats in saltwater year around tells me that attaching a zinc to the frame of the coach and replacing it as it digests is the only real solution once the repair has been made.........
John
30369

Re: more on corrosion

Reply #1 –
Yahoo Message Number: 14189
Good post. Thanks for pointing out things I would not have considered due to my lack of knowledge of this electrolysis action. I can live with the unsightly door but it is a shame for such an otherwise solid coach. I still like the idea of a mural separated chemically and mechanically from the door. I was thinking of rivets or screws and not adhesive to attach it but you make a good point of corroding of the fasteners. Well, back to the drawing board.

George Becker
gwb36@...
1999 Country Coach Intrigue
Cummins isc350
Coach #10700

Re: more on corrosion

Reply #2 –
Yahoo Message Number: 14190
Using a zinc anode is a possibility. However, all the structural components of the coach would have to be "electrically bonded" together. The door typically could become isolated from the rest of the frame because of the hinge design. Lubricants and road crud will electrically isolate the door and would get no benefit from a close by zinc anode.

Of course, there is no guarantee the anode will even work if the corrosion has already started. Depending on the type of aluminum used for the skin, the corrosion can turn into inter-granular corrosion. In this instance the corrosion can continue to propagate on its own with an electrolyte such as water. This in its true sense is electrolysis. I know working with designing repairs to military aircraft, 2024, 6061, 7075 and 7071 type alloys are all susceptible to inter-granular corrosion. Use of stainless on the exterior would not be a good fix either.

I think the best action is to have a shop reskin the door using an inert material. That is apparently what was done by CC to my door when the original owner had it. I understand that they made up repair kits using fiberglass skin panels. I can see the ripples in the surface on my door when the sun shines on it the right way.
Obiviously, a rush job on the layup and gel coat. But, I can live with that better than the corrosion.

Jim Hughes

2000 Allure #30511

Re: more on corrosion

Reply #3 –
Yahoo Message Number: 14193
So if the door is grounded to the coach will this help? That way the door does not become isolated..Just wondered..We have a new 05 intrigue and would love to be able to do what ever it takes to reduce the chance of future problems.

BTW this is a great forum

Russ and Jean
Intrigue #11883

Re: more on corrosion

Reply #4 –
Yahoo Message Number: 14228
I am not familiar with the construction of the new coaches. I know they use a different door design than my 2000 Allure. I was responding to John's comments about an anode on his coach which is closer to my design. I would suggest you contact Country Coach and ask if the door on your coach is aluminum skin or is it fiberglass or some other inert material. If it is not constructed with two dissimilar metals (i.e. aluminmum skin on a steel frame), then you have a much better chance of never seeing any corrosion. If the door still has the corrosion prone design, then ask Country Coach what have they done in the design to protect the door. Electrically bonding the door to the frame may do no good depending on the design.

Jim Hughes

2000 Allure #30511

Re: more on corrosion

Reply #5 –
Yahoo Message Number: 14284
CC has a fix for this problem. They supplied me with a fiberglass skin to replace the aluminum skin along. While they supplied the new skin it will not be an inexpensive repair as the new skin needs painting.

You may want to call CC to see if they are still supplying the replacement fiberglass skins.
Joey

1998 Intrigue 10540

corrosion

Reply #6 –
Yahoo Message Number: 14194
I think you will find that at least two wires will be attached to the internal door frame at some location (rather I should say taped)......entry door step power and patio light. Most certainly depending on the coach there could be more.
Another correspondent mentioned bonding or a common grounding line would be required before using an anode. Although it may be a royal pain to maintain, an anode could be attached to the steel door frame internally or a grounding line could be attached to the frame and an anode installed there to a bare portion of metal. That should prevent corrosion from beginning, it won't stop that which is already infected.

My reading here tells me that this is not an isolated event (mine) although talk to CC and expect a different answer. With specific regard to the Allure, it has the same combo material baggage doors while those on the Intrigue are fiberglass. The baggage doors show absolutely no sign of corrosion...so the mystery continues.
As an aside, the "door manufacturer" no longer makes these doors and the supply at CC seems to have been exhausted.......

John
30369