GALVANIC CORROSION: CARBON FIBER + ALUMINUM | What is it? How we prevent it on the DarkAero 1!

[@DarkAeroInc]

For more composites related knowledge check out: www.darkaero.com/knowledge/composites/ Want even more? We also offer consulting: www.darkaero.com/consulting

[@ready-to-race]

Thank you for the video! Do you have an example on any parts with galvanic corrosion? I'm looking for some photos or video as some evidence that corrosion is an issue in discussion I had.

[@SkypowerwithKarl]

I see galvanic corrosion in all kinds of places with things you wouldn’t expect. On marine fuel tanks where the filler hose connects is very common. The hose is Coast Guard approved, wire reinforced rubber. When people put double hose clamps on at the very end of the hose it leaves a space above for moisture to collect between the hose and aluminum tank inlet tube. Well this moisture is a combination of condensation and fuel which turns acidic. When you have this acidic (electrolyte) in proximity of aluminum and the carbon black in the hose you get corrosion...lots! The solution is to place one hose clamp on the hose so it’s around the top of tank’s inlet tube and the other at the hose end. No accessible space to collect moisture. Yes there will be some limited corrosion at the top edge but it’s a non issue. Another place is the sender gasket. It’s made of chopped cork and rubber. Cork to wick and hold moisture and the carbon black in the rubber....perfect right? I replace these with fiber reinforced silicone gaskets. Same for metal tank straps, the the elastomer between the tank and strap can’t be rubber and a firm polyurethane is best. Devil in the details to make it right.

[@edthompson9569]

You are a gifted teacher! One small correction. Physical contact is not required for galvanic corrosion. The electrolyte is all that is needed to put two dissimilar metals in electrical contact. That's why the sacrificial zincs on a steel boat protect the entire hull and attachments.

[@lovrepeovic]

Metallic contact is neccessary.

[@jonasurfer4785]

@@lovrepeovic simply wrong

[@lovrepeovic]

Your knowledge of the problematics of galvanic corrosion on boats is obviously not sufficient. I do this for a living.

[@laurens4359]

@@lovrepeovic Metal contact is not necessary - e.g. the non metallic charge carrier will allow for corrosion, e.g. en.wikipedia.org/wiki/Galvanic_cell

[@ivanalvarez5511]

@@lovrepeovic only electrical contact is necessary, not necessarily physical contact. Meaning an electrolyte is sufficient. Think of electroplating

[@CanineDefenseTechnologies]

I've been designing a carbon fiber rocket and thought oh shoot I should've known this, until the end lol 😂

[@andrewstambaugh8030]

Great video and very good discussion of the various ways to handle this. I liked that you gave a warning about which side is better to paint (to avoid a focused corrosion attack at a scratch). thing that could possibly misleading people (your written description states this correctly, but doesn't call attention to it). [I'm sure you understand this very well, but for the sake of anyone watching who isn't familiar.] In your talking discussion, you say if the 2 metals/materials are touching, but: the 2 metals don't have to directly touch, as long as they are electrically connected, e.g. any bolt, wire, metal frame, or stray piece laying across them can act as a wire and electrically connect them. Example: If you are trying to protect your Alu by it touching copper, then copper to nickle, nickle to... up the galvanic chart. If the electrolyte connects from alu to the high galvanic (SS, titanium, or carbon fiber), it will cause high corrosion/galvanic corrosion, similar to if they were directly touching. (think of galvanic corrosion as being a battery like effect). In the marine industry, I have see some examples where people left tools or spare parts laying across things, that completed the circuit and caused excessive corrosion. (or commonly a found mistake, just left a spare SS pump or hydraulic fitting sitting on ALU where moisture would splash or condense.) It's also worth mentioning to people that Alu is praised for how it naturally forms a patina/protective layer, not rusting and pitting like steel... unless you galvanically corrode it! Then it pits deeply and turns to crumbly powder!

[@travers114]

Thank you guys so much for making these videos. So interesting and informative. This video is probably the best intro to galvanic corrosion on youtube.

[@whatelseison8970]

Some other good options include anodizing aluminum parts, and for metal objects that will be buried or immersed in water, cathodic protection is great where a steady source of power is available. Where it isn't you can always put your aluminum parts in contact with an even more active metal like magnesium (a sacrificial anode). Nice video. I enjoyed it.

[@fallencorporal]

I was wondering why they didn't consider anodizing it. It may have not been an option because they're connecting aluminum directly to the resin, the layer of aluminum oxide might prevent it from sticking altogether.. I'm sure google would be able to give an answer on that.

[@MichaelT_123]

For small aluminium elements consider to finish them with the electroless Ni-P amorphous layer. The parts will be not only corrosion resistant but also light and ... shiny! Good job!

[@ddegn]

I'm a chemist myself. I thought your video was fantastic.

[@Danieltredway1431]

You guys are so generous with your information. God bless you guys. I am tired of companies being so greedy with information. We need companies like this who have integrity and generosity. I always believe sharing will win because people will learn to trust you guys more because people want to know what they are getting to make the best decision. I also believe God will bless you more in the end.

[@PH-G]

Love the drill bit pointer!

[@DarkAeroInc]

😁 Good eye! The drill bit is more my style.

[@dnogin]

You really have a deep dive into the issue. Enjoyed watching it.

[@felixlabelle9041]

Very interesting dive into galvanic corrosion and the issues in bonding CF with metals. That disposable rocket exemple was awesome. Thanks for making this information public and engaging :)

[@rigilchrist]

It is impressive that you have such deep materials knowledge and a willingness to share such detail. It also evokes confidence in your product. One question: what about the exposed cut edges of the aluminium honecomb, such as you showed in the aft fuselage. Wouldn't water on the cut edge bridge the skin and core? (I appreciate that you are changing the core material for production, but I was just curious). Thank you again for you wonderfully educational videos.

[@DarkAeroInc]

Currently, we seal up exposed honeycomb edges with assembly adhesive but we are also testing out some other low density fillers. Thank you for watching!

[@iloveaviation-burgerclub-a8145]

You do a pretty good job. I think GC is one of the most forgotten things. Not sure. But guessing that many builders don't pay too much attention to it. Best case this ends up in high maintenence action by getting all these bolts our or nuts off, pins out and boring things like that. Paying attention also makes life so much easier on the metal side. Good luck for your project.

[@zolotiyeruki]

I have two questions: 1) In a previous video (July 29), you walked through your process for selecting aluminum honeycomb as the core rather than using off-the-shelf panels with aramid cores, and mentioned temperature performance as a factor. Is the temperature issue a result of the aramid core itself, or is it due to other factors in the construction of the off-the-shelf panels? 2) How did you give the fiberglass layer the same honeycomb pattern as the core? Or is it a continuous sheet that just looks like it has the honeycomb shape because of how it was pulled apart?

[@justinw1765]

Aluminum is far more thermally conductive than aramid material.

[@C-M-E]

Late to the party as usual, but this an interesting area of study that has been arguably been tackled across a lot of different industries. In racing applications, ironically one of the first uses of bi-material composites, they don't particularly address it well, as most platforms are seen as essentially a limited lifetime chassis. Once it begins to form, the clocks are ticking on replacement. Aerospace is a little different, where coatings and even sacrificial anodes are used, both with pros and cons. Maintenance is generally high in this space, so upkeep of sacrificial bits go with the territory. The sacrificial route is also used in heavy cargo ships and waterway bridges. One of the somewhat overlooked areas particularly of concentration with aerospace is material interaction with static air charges building on operating and structural surfaces. Isolation in the core structure helps, but also needs a secondary strategy as the charge can build in operation beyond design specification depending on operating environment (naturally, you don't have much choice here).

[@justinmoritz6543]

Awesome videos! I’ve been loving these technical videos you’ve been making. Helping me understand engineering a WHOLE lot better

[@DarkAeroInc]

Justin, that's great to hear!

[@sunworksco]

As a commercial plumbing contractor, I’ve seen horrible commercial plumbing systems, like the Massimo clothing factory. A very careless installation plumber originally installed all of the copper water piping systems with no dielectric couplings on the copper to iron pipes and fittings and just several years later, all of the copper tubing, as large as 6” diameter copper pipes had hundreds of pinholes and had to be removed and replaced. The interior of the factory was similar to a greenhouse mist system!

[@crawford323]

I served 15 years on 500 ft research vessel and one of the ways the marine industry fights galvanic corrosion other than sacrificial metals was to electrify the hull with a very weak charge to nullify the difference in charges. I thought this was clever.

[@kellypyatt3144]

Very cool. i was wondering when you were going to talk about this.

[@fly4fun24]

You couldn't Find a better Wand , I loved it along with knowledge I just Learned... You guy are bulding a very fine piece of Engineering..

[@augurelite]

These videos are awesome! Love watching the DarkAero progress :)

[@DarkAeroInc]

Thank you for watching! Glad you are enjoying the videos!

[@drewski23_7]

Love that he used a drill bit as a pointer!

[@HappyQuailsLC]

This was very helpful because we see a form of this take place with ancient artifacts which have been in the ground for many years.

[@christopheraugustine5816]

Regarding the part about sealing things away from moisture, all I could hear was my father's voice. "You can never seal water out, all you can do is trap it inside when it gets there." Great video! Also, where do you get the honeycomb materials?

[@rooster700rr]

5:14 when you realize your professor is using a really long drill bit is as a pointing stick. (trust me, that is the correct technical name for a pointing stick, I googled it because I thought it would for sure, have a fancier name:)

[@gurdogarsargul9621]

Hi when you talk about galvanic corrosion you should also consider your SS bolt touching aluminum same problem, I have seen this in your video. Your aluminum parts will be corroded where touching SS. I have seen this in many airplane. I am building aluminum boat so have some serious experience on this subject. Try to use Tef-gel between dissimilar metal. You must also be very careful when electrification and wiring of your plane, always use two-polar thermal switch and never use ground pole. Success in your project.

[@danielbasovitch5087]

Riley, what is your background? Aerospace engineer? Physics professor? When you talk and explain what your doing it is so comprehensive, it sound like a script, but I know it is not. It takes very qualified and intelligent people to design and build this BULLET!

[@madtownbadger7115]

Nice work, Ryley, very simple explanation. This conversation is typically much longer than 12-mins in most meetings. Whether we are building a profile for farm equipment or a satellite at Exel Composites, fiberglass tends to be a cheap insurance policy against galvanic corrosion, with proper Resin selection.

[@DarkAeroInc]

Thank you Jared! It was actually a real struggle to condense this topic down so I wouldn’t feel bad if it took longer to go over this in a meeting! 😁

[@rustusandroid]

The air inlet, I feel, would be a good place for fiberglass use. The plastic will deteriorate over short time with the heat changes becoming brittle. It will be a constant replacement part.

[@MM-24]

so....why did you use aluminum honeycomb at all? What are the detractors of using Aramid? why wasn't that chosen in the first place? why don't you use carbon fiber honey comb?

[@danielmiller2886]

Thank you!! Great info for us who aren’t (officially) engineers but still need detailed data and instruction.

[@RBAERO]

Very nice video! Question how you prevent corrosion on bolts and nuts like does we see on linkage at 5:55

[@evangatehouse5650]

In the marine world, we try to avoid stainless and carbon fibre. Not as bad as aluminium but you will see corrosion. Titanium is preferred for critical connections

[@tuckpilot1192]

Nice job, professor. You're putting Khan Academy on the defensive...

[@rankarahul18]

Khan academy is a subtle propoganda machine twisting facts

[@TheJustinJ]

@@rankarahul18 stick to the maths.

[@EDesigns_FL]

If you anodize your aluminum parts, it will render the surface non-conductive. An additional benefit is that the surface will also be harder, particularly with type III anodizing. Though this may not be practical for aluminum honeycomb, for most parts it may be a better option. I liked your presentation of this subject: informative and concise ;-)

[@kcsnow9447]

I might have run into this issue in an old house, wherein I was attempting to have a plumber bring a natural gas furnace back online after five years or so of non-use. Black iron pipe used most everywhere, but galvanized metal elbows in the corners...and he started frowning when he looked at it closely. "These elbows were intended only for water mains, and whoever built this (back in the 1950's) should have known this...but just might not have known about it." This Old House, indeed.... In the end he went all the way back to the meter, and started over again, as those elbows were used in every bit of the gas main. So: Is natural gas considered an electrolyte bridge? Are galvanized pipe and black iron actually dissimilar metals? The metals were certainly in contact with one another, and the gas circuit was certainly grounded.... BTW, I'm not just some lost homeowner asking this, as dad had purchased and were starting to build an RV-6 until we realized the cockpit was too vertically confining for comfort, and the alterations were going to be very difficult and time-consuming. The RV-10 I tried on for size at our local airshow fit both of us (tall guys) a whole lot better...but then his health began to fail and that brought an end to the project. Even though he's gone, I'm still paying attention. "Go, men, Go," and thanks for the very informative videos!

[@anidiotinaracingcar4874]

Have you done a video in which you compare the strength of your honeycomb with something else (say a foam core, for instance)?

[@callsigncrusader9877]

My professor need to see this 😒 I mean seriously, Riley make it so easy to understand

[@DarkAeroInc]

Thank you! :)

[@truth7416]

I totally understand because of the simply clear way of your teaching. You need to consider starting a composite school.

[@91rss]

met someone who said in their job they use stuff called Mastinox to stop it between bolts placed in aluminum. never an issue .

[@tomcoryell]

Thank you very much for this. It changes my material choices for a project I have in mind.

[@danielleriley2796]

The aramid honeycomb would be excellent in areas that are permanently sealed and as such no access for inspection or easy inspection.

[@kashimakun7577]

I made carbon fiber plate with 3d print ABS honeycomb, its really Work

[@theperson7718]

So what's the actual part of carbon fiber that's conductive? Is it the carbon fibers themselves or the bonding agent AKA resin? If it's the fibers themselves then well I guess there's nothing to do but if it's the resin then couldn't some of the resin companies make a non conductive resin to solve all these problems? Great video by the way. 👍

[@1312iYo]

Great video, very informative yet easy to follow along! Having the prototype to show the different solutions added a lot!

[@DarkAeroInc]

Thank you and thanks for watching!

[@crawford323]

I had no idea that a composite and a metal could have galvanic corrosion. Of course this type of corrosion is based on electrical potentials. It is amazing the battles which are fought when we make strides with technology.. so the old saying that it’s ok to be on the leading edge of technology just not on the bleeding edge.

[@manjus7063]

Brilliant teacher! Love your videos.

[@solidkreate5007]

Yep we used that Nomex too. Been cut many times by sandwich panels.

[@robertcloudman3676]

What is the weight difference between your sandwich panel core choices? It was the hardware rot going thru sandwich panels that got on my nerves. I went to stainless almost as soon as components were built. Corrosion slowed significantly but never eliminated totally. Silicon helped but not 100%

[@jaypie0864]

Learned this years ago but this was such a better explanation!

[@DarkAeroInc]

Thanks Jay!

[@marcoangelini2642]

fiberglass, even if thin, weighs a lot on a large surface, NOMEX is better for airplanes. I put the double fiberglass insulation on the anodized aluminum inserts mounted on the boats. Anyway, thanks for the details you provide! all laminators should have this knowledge before they get their hands on the piece! here in Italy some companies are not required to give certain explanations to their workers! It almost seems like a secret!

[@williamreymond2669]

7:11] You haven't mentioned it, so I'll mention it, *cathode to anode surface area ratio (Ac/Aa).* Ac/Na ratio is the idea that when a large surface area of carbon composite material [anode] is coupled to small metallic parts such as: fasteners, bolts and nuts [cathode] the rate of galvanic corrosion can be extremely high. Galvanic corrosion on steroids in other words.

[@sefutho]

Wow! This would certainly help me a lot, thanks.

[@aaronokimoore]

Learned a lot! Your overview of the principles and going into the methods and options was really insightful. Curious, how you are doing accelerated testing?

[@robbeelsas]

Probably in an extremely humid test chamber with lots of salty water vapor

[@Rollingwrenchsnowbikes]

The early carbon fiber snowbike kits had some issues but they fixed um with some fancy magic

[@mtcondie]

Waiting to see what changes are incorporated into the DarkAero 2.

[@luigigalvani9601]

Bel video! Sapevi che ho inventato questo tipo di corrosione?

[@Colorado_Native]

Just came across this channel. The SR-71 had a lot of titanium. To prevent GC a lot of the tools the mantainers used were also made of titanium. The USAF paid how much for one screwdriver? I can buy one at Home Depot for $2!

[@PoulHansenDK]

Thank you. Very Thorough and effective explanations..

[@The_R_Vid]

Any time an Engineer breaks out a whiteboard, I know I'm in for a real treat! I'm sure Jason from @Engineering Explained would approve this video.

[@DarkAeroInc]

Engineering Explained has some great videos! We might have taken some inspiration from his whiteboard explanations. :)

[@braydend9582]

Have you thought about coating the aluminum parts with Cerakote H-900 Electrical Barrier or a similar product when in direct contact with carbon parts? I know you could anodize the aluminum parts but they would lack corrosion/chemical resistance. There are also dielectric epoxy adhesives that could be used to glue carbon and aluminum but I doubt they would have the same mechanical properties. All this extra coatings and work might just be extra since they might outlast the life cycle of the parts they are being applied too.

[@koffeekage]

Cruisers have a major concern with this, the superstructure is made of Aluminum and the hull is steel, combine that with seawater.

[@ΠαύλοςΡακοβαλής]

You Guys are AWESOME. Keep up the good work. Thanks for the videos

[@lucasvinholigoncalves8829]

Great vídeo, congrets to the awesome teacher 👏👏👏

[@DarkAeroInc]

Thank you! I never really thought of myself as a teacher but I must say that trying to put together a short video on this topic gave me a much greater appreciation for the professionals who teach!

[@sw6006]

With your suggested change in the core material are you going to have to go through all the structural and vibration testing again?

[@DeksZagreb]

Why did you not opt for cork as the sandwich material between two layers of CF? It might be even stiffer than aluminum, and completely remove any galvanic corrosion risk.

[@justinw1765]

Galvanic corrosion is one thing, but how do you deal with the dissimilar expansion/contraction between carbon fiber and Al core?

[@trumanhw]

Alternatively ... did you guys consider using sacrificial anode..? Or inconel (not much more than steel)..? It's supposedly pretty resistant to corrosion.

[@DMAX_DIY]

Very nice guys.. I'm trying to get some A HC for my CF project (which is a motion simulator). Nice information DMAX

[@DarkAeroInc]

Thanks for watching! :)

[@solidkreate5007]

I figured you used some type of thick plasti-film between the layers before you MOP it. I didn't know fiberglass would work. That is really cool to know. Funny story, I have used those EXACT click bonds when I worked for a very large aircraft manufacturer (laid off covid-19) where her Majesty used to be built. I was an Assembler before I became a Manufacturing Engineering Planner II.

[@ReflectedMiles]

It's a good start theoretically. The real test will be after it's been sitting in a warm coastal environment for a decade or two. What kind of defense will your carbon fiber have against the enemy that is worse than stopping bullets: raindrops?

[@0623kaboom]

your definition of galvanic corosion was ALMOST correct it is not between metals though it is between electrically conductive parts of differing resistances .. as long as it will conduct electricity it will corode . the fact that most metals are electrically conductive makes this most common with them ... even sodium and carbon will corode .. when in the right conditions and NEITHER is a metal ... BUT they are BOTH conductive ... in this case the carbon fiber would be eaten away while the salt will change to black

[@wanderingfirbolg6738]

That's pretty common on older aluminium car bodies when placed on Molybdenum steel alloy spaceframe chassis.

[@44hawk28]

The Nomex should also be more fire resistant. Aluminum does not have to get particularly hot before it starts to become molten and when it is molten and encounters water it can become explosive. However I don't think you have enough aluminum in that aircraft to worry about truthfully.

[@TheJustinJ]

Geez, it's a good thing they don't build airplanes out of that stuff!

[@Thomas..Anderson]

Watching second video was enough to subscribe.

[@mayakovski]

I think ya broke my brain. Great explanation.

[@hugoramos9481]

Hi there, is there a posibility to pasivate the aluminion core through anodization? does the anodization change the aluminium mechanical properties? did you consider this option?

[@jerrymcarthur2062]

did you guys test how anodizing aluminum effects it?

[@jasonshipp3502]

Just add a few layers of Fiberglass on the top in the bottom of your carbon fiber layer or whatever layer is contacting that could pose an issue.

[@KarlOnSea]

Excellent video, thank you. 👍

[@johnmorey5166]

To prevent the galvanic corrosion :- must I insert an insulating layer between the Al and CF blocks in your diagram OR can I insert a thin titanium sheet to separate the Al and CF blocks which will still let the current flow but create Al/Ti/CF interfaces and not corrode in place of the Al/CF interface ? Cheers John

[@danbenson7587]

Aluminum and epoxy go ill together unless the former is anodized. Slightest humidity oxidizes the bond line.

[@ja2706pw6u]

Very Nice Video !!! I learned a lot !!! Thank you so much !!!

[@promodracer2191]

Could you discuss carbon fiber printing, or a solution for the carbon fibers printing into a painted carbon finish hen exposed to sunlight and heat from sun.

[@dave1812]

i didnt even know carbon fiber could cause galvanic corrosion. but it's logical if you think about it

[@dariodamico3033]

What about grounding carbon fiber panel to discharge static electricity? How does this play into this? If you isolate the CF you don't discharge anything with the risk of charging the part.

[@flyfaen1]

I was about to say; "But why use alucombe, when there are better composite alternatives. Unless you are intending it to be a crumplezone..." But you mostly covered it in the end :p

[@ExploreComposites]

Great video! Thats a nice way to handle the problem and I bet that thin ply of glass doesn’t add much weight overall. Will the switch to Nomex save you weight too or just improve the manufacturing process?

[@DarkAeroInc]

Thank you! The production change away from aluminum will provide a slight weight reduction and improvements in manufacturability.

[@nilosantos9715]

Tanks for sharing information

[@justinw1765]

I don't understand the use of nylon on that one part, when S-glass fiberglass is far, far stronger?

[@ДмКр-з6с]

Hi DarkAero, This is very informative video. Thanks for that! One small question. It could be seen from video that fuselage honeycomb sandwich frames edges also bonded to carbon fibre skin. How do you fight GC here or how are you ensure you frame's aluminium alloy core does not have contact with fuselage skin?

[@scettzvill]

a 3d printed nylon inlet is non conductive. but isn't nylon highly susceptible to building static charge? how would that effect the contacting aluminum surface?

[@kadecooper246]

What is the pros and cons of nomex vs aluminum honeycomb structure?

[@DarkAeroInc]

Great question Kade! For the specific type of aluminum and aramid cores we are using, aluminum has a slightly higher strength to weight ratio and it is lower cost than aramid. However, aluminum core is a little harder to bond to the face sheets and it requires the added fiberglass layer for corrosion protection. The main reason we are changing to all aramid for production is we find it easier to work with in a mass production environment. Thank you for watching and for the question!

[@gdu370]

Does the galvanic corrosion ultimately strengthen of the carbon fiber with the increase of electrons

[@arthurtencate]

Very educational videos, great stuff you're sharing. How do you cope with aluminum toggle switches and cfrp instrument panels?

[@tanle7164]

Didn't know where the O2 came from at first, so I was dumb enough to forgot what I'm breathing lol. Great vid though.

[@PaulTheWonder]

Great video!

[@LaserRifle]

Dumb question, but can carbon fiber damage plastic if it's touching it for years? Is there a reaction between CF and polymer or other plastics?