Steel CCC or CCP rivet on aluminum part

[Sacpilot]

No problem at all Tony. Yeah, I agree! It's 75 degrees here. Build on!

[Tony Spicer]

Christopher,

Don't know why, but I assumed you were discussing skin rivets.

Time to turn off the computer and build an airplane

Tony

[Sacpilot]

"you should try to have a large anodic area (aluminum) and a small cathodic area (stainless steel)" this tends to support the use of ss rivet in aluminum vs (aluminum rivet in steel such as zenith 750 skin to fuselage)

I didn't choose SS, the CCC and CCP are ss rivets. They came with tail kit for the stiffeners/spar and hinges to skins/spars

Clearly any electrolyte (salt) will speed up the process. I could have chosen any one of 1000 websites, here is one:

http://cr4.globalspec.com/thread/6690/G ... d-Aluminum

For the record, go to the marina at any Coastal environment, and look at an aluminum mast, with stainless steel fittings and rivets. There will likely be corrosion unless there is an insulator in a paint, gel, or non metal washer applied. I know Sonex does it and I am totally fine with the use of no primer/insulator on a 6061 structure due to its same consistency all the way through, and comfortable with aluminum pop rivets without insulator on aluminum structure. Just wondering about SS rivets on aluminum.

However, I just found this. I think this might suggest that it is ok. One thing the Brits know well, is moisture in the air, and marine environments. And this is from the British Stainless Steel Association.


http://www.bssa.org.uk/topics.php?article=89

[Tony Spicer]

Christopher,

John Monnett has been using stainless rivets in the Sonex (6061) since the mid 90's. And in the Sonerai (2024) since the mid 70's.

My Sonex was two miles from the ocean while being built, then spent 5 years in a hangar 10 miles from salt water. No paint, no primer. And no signs of any corrosion.

Why did you choose stainless rivets over aluminum?

Tony

[JimParker256]

I did what you suggested, and Googled it. Everything I saw that looked like it was written by a metallurgist or scientist seemed to indicate that stainless rivets in aluminum structures are probably OK, whereas aluminum rivets in stainless structure was highly prone to corrosion. Has to do with anode to cathode ratios, apparently.

That said, I have no special knowledge in this area. Just found it interesting that following your own suggestion alleviated my concerns.

On the other hand, I would be more concerned about installing rivets with anything on them that would be classified as a "lubricant" and that might allow those rivets to "work" more easily. But again, that's just my "gut" feeling with no experience or knowledge to back it up...

Hopefully someone with more knowledge will chime in...

[Sacpilot]

Well, after some research, Lanocote, as its lanolin, will run when warmed making it less effective in a hot airframe. TefGel is more expensive, but won't change from gel in heat. Marelube seems to be less expensive TefGel and more of active ingredient. Also, from what I can tell, there isn't a solid rivet that has a higher strength than ccc or ccp rivets unless you go up a size. So thats out.

So, unleas I find out something to the contrary, it will be ccc and CCP rivets dipped in Marelube gel or TefGel bc it doesn't break down in heat, and it doesn't contain silica. Will prevent metal to metal contact and it will allow rivet to move better during assembly for tighter fit.

[Sacpilot]

Keep in mind, I am not talking about all over the plane, I'm only talking about the few places where stainless steel and aluminum meet, such as the CCC or CCP rivets, or a cadmium AN bolt. That's not too many. Maybe under 100 in HT spars to stiffeners. If you have seen a aluminum mast in a sailboat with steel hardware or fasteners, even inland, you would know why I am asking. I know we need a stronger sheer tensile strength here, hence the CC series, but doesnt the dissimilar issue trump the strenth, requiring a solid aluminum rivet like the wing spar? On the chart of metal differences, the stainless is more dissimilar than the normal steel mandrel in a normal aluminum rivet.

Was thinking of using TefGel, Marelube , Duralac (barium chromate paste) or Lanocote, which can be applied with a little toothbrush or dip the rivet, (Lanocote is food grade) between shop/factory heads and stiffeners and any aluminum parts. I would use these bc not as messy to apply as zinc chromate paint. Boeshield, Corrosion x, and ACF, are more penetrant sprays than a gel or paste that could "stick" on the rivet between surfaces. There isn't any issue with aluminum rivets on aluminum structure, or steel rivets in 4130 tubing or a hinge, but together they kind of ask for problems on a critical area like spar don't they?

Not trying to stir up a bees nest, just want to prevent issues. Google stainless rivets into aluminum and see images. I'm sure Dan/Paul took this into account when designing, so I'm looking forward as a novice and occasional sailor as to thoughts on this from the community.

I think I'm more sensitive to issues on critical parts on this plane given the aerobatic nature vs the 80 mph airframe of the 750 I built.

[Sacpilot]

I've read all the priming posts, and the debate on priming. Not looking for long discussion. I'm not priming my plane, but I thought about priming aluminum surface quickly with NAPA primer where steel rivets are used in aluminum. My understanding is this is the one place where dissimilar metals will definately start corroding, in any environment.

Any quick thoughts on using Napa rattle can as an insulator between heads and part on a place like the HT stiffener/spar? Not interested in wet dipping rivets, although this would likely be the best measure if I wanted to take the time.

Thanks.