Corrosion within the laminate

Any DA40 related topics

Moderators: Rick, Lance Murray

User avatar
rwtucker
5 Diamonds Member
5 Diamonds Member
Posts: 1283
Joined: Thu Feb 21, 2013 11:24 pm
First Name: Rob
Aircraft Type: DA40
Aircraft Registration: N831BA
Airports: KFFZ KEUL
Has thanked: 100 times
Been thanked: 110 times

Re: Corrosion within the laminate

Post by rwtucker »

Lance Murray wrote:The root cause of this issue is that you should not bond carbon and aluminum together. This was an idiotic design failure. "Fiber-reinforced plastics are corrosion resistant, but plastics reinforced with carbon fibers can induce galvanic corrosion in attached aluminum structure."
Great point. Thanks for digging this up. Before that, I was trying to figure out what would be serving as a cathode in that bonding. The dope slap was Boeing's table embedded in the article you referenced. I was visualizing the carbon fiber as embedded in the more-or-less insulating epoxy resin. [Slap!] http://www.boeing.com/commercial/aeroma ... ble01.html
User avatar
Steve
5 Diamonds Member
5 Diamonds Member
Posts: 1953
Joined: Thu Aug 12, 2010 1:23 am
First Name: Steve
Aircraft Type: DA40
Aircraft Registration: N432SC
Airports: 1T7
Has thanked: 81 times
Been thanked: 493 times

Re: Corrosion within the laminate

Post by Steve »

I don't believe that there is any carbon fiber in the area in question.

Steve
User avatar
CFIDave
5 Diamonds Member
5 Diamonds Member
Posts: 2678
Joined: Wed Nov 07, 2012 3:40 pm
First Name: Dave
Aircraft Type: OTHER
Aircraft Registration: N333GX
Airports: KJYO Leesburg VA
Has thanked: 231 times
Been thanked: 1473 times

Re: Corrosion within the laminate

Post by CFIDave »

It sounds like the potential for galvanic corrosion might be a bigger issue for DA42s than DA40s, since the DA40 only has a small amount of carbon fiber (CFRP), including the "roll cage" around the cockpit, and parts of the wing spars. Otherwise everything is fiberglass (GFRP).

In contrast the DA42 has more carbon fiber than fiberglass, including carbon fiber engine cowlings, wings, and fuselage/tail. The only large fiberglass surface on the DA42 is the rear horizontal stabilizer.

While not as old as steam-gauge DA40s, early DA42s will soon be more than a decade old.
Epic Aircraft E1000 GX
Former DA40XLS, DA42-VI, and DA62 owner
ATP, CFI, CFI-I, MEI
User avatar
rwtucker
5 Diamonds Member
5 Diamonds Member
Posts: 1283
Joined: Thu Feb 21, 2013 11:24 pm
First Name: Rob
Aircraft Type: DA40
Aircraft Registration: N831BA
Airports: KFFZ KEUL
Has thanked: 100 times
Been thanked: 110 times

Re: Corrosion within the laminate

Post by rwtucker »

Steve wrote:I don't believe that there is any carbon fiber in the area in question.Steve
Copper?
User avatar
Steve
5 Diamonds Member
5 Diamonds Member
Posts: 1953
Joined: Thu Aug 12, 2010 1:23 am
First Name: Steve
Aircraft Type: DA40
Aircraft Registration: N432SC
Airports: 1T7
Has thanked: 81 times
Been thanked: 493 times

Re: Corrosion within the laminate

Post by Steve »

rwtucker wrote:
Steve wrote:I don't believe that there is any carbon fiber in the area in question.Steve
Copper?
Actually, I went home and looked at the AMM tonight. There are actually areas of carbon fiber in both the top and bottom of the wing, but the diagrams are not sufficiently detailed for me to determine if it is in the grounding strap area. The fuselage center section adjacent to the wing does not show any carbon fiber laminae.

Steve
User avatar
ihfanjv
3 Diamonds Member
3 Diamonds Member
Posts: 93
Joined: Sun Dec 04, 2011 8:00 pm
First Name: None
Aircraft Type: DA40
Airports:
Been thanked: 7 times

Re: Corrosion within the laminate

Post by ihfanjv »

This corrosion is not carbon-only related. As any boat owner will tell you, once the composite is penetrated and not sealed the composite will start to delaminate due to water intrusion. If you drill a hole through composite you are supposed to seal the inner surface of that hole with polyester/epoxy/some other sealer - this is not done in any hole that I have seen in the Diamonds. Composite aircraft that are left outside fair far worse than hangared airplanes, but even hangared planes will suffer water intrusion related delamination over time. Where you have metal in the composite, that just means it will start to corrode even in ambient air - no water intrussion required. If you have a composite sandwich, then put an aluminum mesh in the composite, then bond carbon in the composite, then put a bolt of dissimilar metal through all of that, then throw in water or moisture, then vibrate it on a regular basis, you are going to get corrosion, delamination, electrolysis - all kinds of problems.

This issue is an inherent design flaw in most composite GA aircraft. I wonder how Boeing and Airbus address this in the composite parts of their aircraft - not just the 787 and A350. They have been using composite parts for decades.
Last edited by ihfanjv on Sat Aug 08, 2015 5:07 pm, edited 1 time in total.
User avatar
Lance Murray
5 Diamonds Member
5 Diamonds Member
Posts: 1163
Joined: Tue Jul 06, 2010 11:25 pm
First Name: Lance
Aircraft Type: DA40
Airports:
Has thanked: 7 times
Been thanked: 118 times

Re: Corrosion within the laminate

Post by Lance Murray »

Somewhere on this site or the competitive site someone detailed the repair process with photos and if I remember correctly this area is carbon directly bonded to an untreated aluminum strip at the root. Yes it is drilled through giving a direct path for an electrolyte to pass giving all the elements of a battery.

In fact every piece of aluminum I have found on my airplane is untreated.
User avatar
Keith
2 Diamonds Member
2 Diamonds Member
Posts: 25
Joined: Sat Aug 21, 2010 9:56 pm
First Name: Keith
Aircraft Type: DA40
Aircraft Registration: N505JP
Airports: KLGC
Has thanked: 1 time

Re: Corrosion within the laminate

Post by Keith »

Does anyone remember where the detailed repair process was illustrated? I remember seeing it but am unable to find it.

Thanks!
Keith
User avatar
Charles
5 Diamonds Member
5 Diamonds Member
Posts: 638
Joined: Thu Aug 26, 2010 5:36 pm
First Name: Charles
Aircraft Type: DA40
Aircraft Registration: C-FLEV
Airports: CYHU
Has thanked: 27 times
Been thanked: 96 times

Re: Corrosion within the laminate

Post by Charles »

The best picture I have ever seen is the one from the first post in this thread which had been provided to me by Diamond.

I decided to get the work done last year at XU Aviation in London ON. A flawless job. Given that it involved grinding all around the section of the wing (top and bottom) along the bonding strip, redoing the layup and fairing, and repainting the entire wing, I thought it was relatively inexpensive. And it fixed the badly chipped leading edge at the same time. The only unexpected thing in the repair was that several flap and aileron hinges could not be taken apart due to corrosion and had to be replaced.

The guys at XU have done more than a few of those and it showed in the speed and quality of the work they did on my plane.
User avatar
Tom-B
3 Diamonds Member
3 Diamonds Member
Posts: 70
Joined: Tue May 22, 2018 9:33 pm
First Name: Tom
Aircraft Type: DA40
Aircraft Registration: N427CQ
Airports: KLOM
Has thanked: 33 times
Been thanked: 24 times

Re: Corrosion within the laminate

Post by Tom-B »

Well, it looks like my 2002 DA40 - with 800 hrs - and has always been hangered at KLOM (Wings, NE of Philly) has joined the club of DA40' requiring repair work to address this laminate/corrosion problem.

While doing a pre-annual walk around with Wing's Head of Maintenance to discuss my aircraft's squawks and the process of conducting the major structural inspection and bonding test we found this issue on both wings. As my A&P tapped the wing with a quarter you could really hear the change in sound as he tapped toward the suspect area.

Has anyone recently had this work done on their DA40/42? If so where and what were the cost of repairs? Thanks

On a tangential note: This was already going to be a big maintenance budget year as I have a new MT prop that should be delivered prior to the annual. Aside from the old prop's cosmetics and the fact the aircraft's first owner never had the prop overhauled the prop has served me well these past two years. But in an overabundance of caution I decided to go with a new prop before problems surfaced. I just did not want to deal with a prolonged down time waiting for a new prop.
Post Reply