SonexBuilders.net

My last aircraft was all composite - no corrosion worries at all.

My new Sonex has bee meticulously treated, during construction, in & out (then painted) with corrosion proofing treatments.

Unfortunately my Sonex will start its operational life parked in the open. To mitigate the effects of weather, I have purchased a heavy duty, custom made, all over, cover BUT still I worry.

The airfield is a long way from the coast & salt and Australia does not (for the most part) use this corrosion accelerator on its runways BUT still I worry.

Am I being unnecessarily concerned?

Should I spray all internal cavities with one of the magic products that claim to control corrosion ?

If so, which one is the most cost effective/popular? (ACF-50, Corrosion X, etc) AND how much would I need to treat a Sonex.

You are being unnecessarily concerned.

Actually - I think you are RIGHT to be concerned. The Sonex is quite lightly built compared to many certificated aircraft. You cannot afford to lose much metal.

Randomness follows:

On the upside - the metal tends to be higher quality than Cessna and Piper were cranking into their airframes 50 years ago. On older aircraft I've seen completely cherry aircraft with whole ribs inside the wing turned to white powder because the metal was from a different batch. Exfoliation corrosion erupting out of nowhere on a flat panel and the like.

As you are probably well aware - a significant portion of the Australian GA fleet has been grounded because when Cessna published a recommended (therefore not compulsory in the US) inspection regime - Australia made it compulsory. The cost (and in some cases - findings) grounded a lot of aircraft.

The reality is that a lot of Cessnas and Pipers have survived through being overbuilt by modern standards. And there are a pile of them rotting in the tie downs that will never fly again. Planes do rot.

I suspect that in Australia you benefit from a lot of drier air - but still corrosion is going to happen. Aluminum alloy skins and stainless rivets is a pretty good little battery on the galvanic scale.

I live and tie down on a salt air coastal airport. After just 3 years in the tie downs altered my regime for the hard to see under surfaces. Frequent fresh water washing is a good thing. I also use "Salt-Away". A chelating agent that is wet film forming and seeps into the overlaps - delivering chemistry that inerts any salt based corrosion products. The US Coast Guard use it on their helicopters. Polish to avoid pitting - because with the best will in the world - it is happening on under surfaces. And then a good wax underneath. To heck with mirror shine underneath. Workmanlike clean.

Visible on top - polish to a shine! :-)

Inside - the faying surfaces were all built with zinc chromate priming. I then bi-annually mist the whole of the interior with Corrosion-X. Frankly - till it is dripping out the seams (don't paint the plane for 6 months - it won't stick).

--

I don't expect a Sonex to last as long as a Cessna. But you put all that effort into building it - be nice if you get to wear it out through flying it rather than have it rot out first.

I do not have any priming of any kind interior of my sonex. Paint on the exterior only. I use corrosion x once a yr. I bought a set of the misting wands (don't remember where but they were a lot cheaper than buying from corrosion x or the AFC50). I bought a gallon of the corrosion x and maybe use 1/2-3/4 qt each time. You don't want it running out the seams but dripping here and there is not too much. As you fly it will drip more until about 4 months later you might not see anymore coming out of the seams. I will usually have a bit on the end of the ailerons and elevators for a few months. I am hangared in a dryish climate but the hangar floor gets VERY wet when it rains and stays that way for a week or two. I don't think you are overly concerned especially how easy it is to do during an annual when all the inspection plates are already open

XenosN42 wrote:You are being unnecessarily concerned.

I'm with Michael. But if it makes you feel better, go for it!

If your Sonex has been "meticulously treated, during construction, in & out (then painted) with corrosion proofing treatments", I wouldn't worry about it any. Sonex is made with 6061 Aluminum, not the 2024 Alclad (pure aluminum surface coat) used on things like RV's and such. As I understand it, the 6061 naturally corrodes "just a little bit" on the surface and then that surface corrosion blocks the air from doing further damage to metal below. My finished and flying Sonex remains unpainted 10 years after completion and is no worse for wear here in the US Great Lakes (albiet fresh water) area. I suspect your nooks and crannys that may be untreated in the past will remain just fine, especially if you cover the entire airframe. (although covering the entire airframe may actually help retain any trapped moisture/humidity and scuff your nice painted finish. think about it)
Happy Landings
John
N50NX