Alodine for rivets?

Use of Alodine

Hi everyone,

I have a couple of questions for our priming experts.

Because the UK is a very wet island, and because I want my future plane to hold its value as best as possible, I have decided to be cautious and prime thoroughly. At the same time I want to stay clear from toxic products and not add too much weight to the plane. I am planning on using Stewart System's (a combination of EkoClean, EkoEtch, EkoPoxy/EkoPrime) which seems to do the job.

Although Stewart System does not mention it (as far as I can tell), I have read in some places that parts should be dipped in alodine before priming. This was initially a non-starter for me as I thought the product contained chromates. However I was referred to this product (Henkel Alodine 5700) which looks like a (relatively) harmless alternative.

My questions:
- Is there a risk that this could have an adverse effect on the efficacy of EkoPrime/EkoPoxy? I'll probably check with Stewart Systems directly.
- Would it improve corrosion protection if I dipped aluminium/steel parts if I decided to use it, or is that completely overkill?
- If I decided to do this, what would the process be? I assume "Clean -> Etch -> Dip -> Prime"?
- I have seen some people saying they dipped their rivets in alodine. Is it a good idea?

Thanks in advance for your support.

Duralac

Hi Patrick,
An alternative way to achieve (in part) what you are seeking is to use Duralac jointing compound. It may be used when assembling dissimilar metals, as well as to install rivets "wet". There is a traditional version that contains chromates, as well as a "green" version that does not. It is made in the UK and is widely used in the boating world... where corrosion is a bit of a problem. I use it in critical areas when building my RV.
Salut,
Paul

FWIW

Usually and primer or conversion that is harmless is also not very functional as corrosion protection. The harmful ingredients are active sacrificial ingredients (like zinc), when there is an open area, poorly painted, ends of sheets or scratches condition. The MIL specs for corrosion protection compare scratched samples. The primary corrosion prevention mechanism of most paint/primers is sealing, not active inhibitors. "Active" prevents that scratch allowing corrosion to run underneath the paint and blister all the while a corroding the skin unseen, underneath.

There are modern paint systems that are still active for a scratch test for 2024, copper alloy without zinc. This alloy has the least corrosion resistance and is why there is a flash coat of pure aluminum on the surface as received. You will have to do some research with your paint company to be sure the "system" is effective against the scratch test. Ask for test results. Then you can address the rivets.

Once deciding on the paint system you can use a wet rivet installation system to apply primer in the riveting process. It is not very practical unless operating off carriers, or seaside runways in the mist demands that kind of protection. Navy's use this.

Dude,

Contact me off list and let's chat - you are waaaaaay overthinking this

Choose your priming system based on the time taken - it is very easy to spend waaaaay too long. Alodine internally is rather OTT (in my view) for a recreational aircraft that will be primed and live in a hangar all its life. Rivets are already covered with something - perhaps anodized? Any coating must resist the setting process!!! As Paul said, wet construction can be used when riveting but is really messy and probably not required. Painters hate it as Duralac never really sets and screws up the finish paint. JC5A is better, if you can get hold of it. Everything is a compromise between weight, cost, time, facilities required and performance. If you're planning to keep your aeroplane outside, next to the sea, then going to town may be worthwhile. Inland in a hangar... perhaps not.

I've used Stewart's EkoPoxy primer as an interior paint. For prep, I've either used their etch or this: an alcohol wipe, followed by maroon Scotchbrite followed by thoroughly cleaning with more alcohol. In both cases, the cured EkoPoxy has proven to be tough and durable.

Dave

Hey Patrick,

Do you even have a RV kit in your possession yet? Do you have any tool?

I realize you are looking for opinions and especially the ones concerning with primers

Here is my opinion:
Visit your local experimental clubs, talk to the builders face-to-face. Go look at the nicer looking RVs or other experimentals and ask the builders how they built their nice airplanes, what primers they used, what preparation steps they took. Take note and at least keep their comments in the back of your mind if you decide to toss them all out. I have met at least one builder who have these various questions jumbled up and prevented him from making any progress for almost 10 years. I have even met one builder who didn't prime anything and finished a very nice RV8 in record time, but he worked full-time on the build .

Thanks for all the answers everyone, I appreciate it!

PhatRV said:

Do you even have a RV kit in your possession yet? Do you have any tool?

Click to expand...

Yes it is early days. I am still waiting for the kit (I ordered from Vans about 4 months ago). My (wonky) workshop is almost ready, I have all the priming equipment and most tools. Not all but but enough to get started at least!

Once my workshop is furnished, I will work on the toolbox/practice kits which I am planning to prime. Not that I care about a toolbox that will outlive me, but just to make sure I have some idea about what I am doing before touching the real plane.

I am asking these questions to check if I need to buy more stuff (in this case, the alodine) which, based on all the answers, I am not going to do!

PhatRV said:

Hey Patrick,

Do you even have a RV kit in your possession yet? Do you have any tool?

I realize you are looking for opinions and especially the ones concerning with primers

Here is my opinion:
Visit your local experimental clubs, talk to the builders face-to-face. Go look at the nicer looking RVs or other experimentals and ask the builders how they built their nice airplanes, what primers they used, what preparation steps they took. Take note and at least keep their comments in the back of your mind if you decide to toss them all out. I have met at least one builder who have these various questions jumbled up and prevented him from making any progress for almost 10 years. I have even met one builder who didn't prime anything and finished a very nice RV8 in record time, but he worked full-time on the build .

Click to expand...

Some of us don’t have access to EAA clubs or airports with lots of experimentals. In fact, even if they did I would be willing to bet that the collection of builders on this site would be a better reference than a random builder you might run into.

Just Saying.

Regarding dipping rivets in alodine, you wouldn't be adding anything.

Per EAA's website:

"To meet AN specifications, rivets must be coated to prevent corrosion. This can be accomplished using zinc chromate, metal spray, or by applying an anodized finish. The latter is usually used."

The anodize can be yellow, gold or clear. This explains the different colors sometimes seen, there is no meaning to the rivet color. Also, anodize is excellent for paint.

I always assumed the anodize was what causes the little puff of smoke you sometimes see bucking rivets.