Weathering a Junkers J.I

[Michael Scarborough]

I just blew the dust off of my WnW J.I kit, one I started when it first was released.  Upon opening the box and having a close look at the pieces I said to no one, "this isn't bad, why did I quit working on this?". Clearly, this is a recurring theme but I seem to be facing it....perhaps I am experiencing the "change of life - male version".

I am considering picking up where I left off but have questions regarding accurately weathering this beast...specifically, would there be rust present?

The blurb from WnW says it was "completely sheathed in corrugated dural sheet. The front fuselage was constructed from 5mm armoured steel".

In reading up on dural and duralumin, I find, "Although the addition of copper improves strength, it also makes these alloys susceptible to corrosion." Huh? "Copper does not naturally corrode." "Aluminum corrodes but it does not rust." 

I will admit to being confused at this point and would rather ask for feedback from the crew than descend into another frustrating situation.

As far as what constitutes the "front fuselage" I assume it is the section shown in this photo that appears to have a haze of rust on it...the section form the prop back to the observer:



As to the rest, if duralumin is primarily aluminum, I would think there'd be no rust visible. As far as corrosion goes, is it safe to assume it would appear as normal aluminum corrosion....all spotty comme ça?:





Someone please send up a flair.

Many thanks,
Michael

[Pgtaylorart]

Michael, from an article I found on the net:         

" The J.I was reportedly well‑liked by its crews, and was first seen on operations during the Battle of Cambrai.  227 were eventually built by the end of the war, and they were first used in significant numbers on the Western Front during the Kaiserschlacht {Kaiser's Battle} of March 1918, known officially as Operation Michael and were used on the Western Front in limited numbers until the end of the war that November."

And:
            "Although this unique design resulted in a strong and durable aircraft that was capable of surviving enemy ground fire, the aircraft was heavy and so cumbersome in its maneuverability that it gained the nickname on operations of  “Furniture Van” from its crews."

"Operation Michael", and "Furniture Van"? Don't you make furniture? Sounds like this plane was made for you!


How weathered do you want it? Would it really rust and corrode much while it was still in service? I would think most of the weathering would be from the sun bleaching the paint and dirt, oil, and grime. Maybe a small hint of rust and corrosion on any unpainted or chipped paint surfaces. As for the copper, it may not corrode, as you stated above, but doesn't it oxidize into a greenish tint like Lady Liberty?

Just my uneducated guesses...

George

[GAJouette]

  Michael,
To the best of my knowledge the blurb you refer to concerns the wings. The fuselage would be built up from 5mm armored steel and would show some rust. The duralumin would not show rust, but show corrosion as in the photographs. The corrosion would be heavier nearest the steel. When steel and aluminum are used together in construction the aluminum corrodes very quickly. I hope this helps you a bit my friend.
Highest Regards,
Gregory Jouette


PS: Thought of another example of this corrosion in a much later German aircraft. The ME.262 had the same problem with the use of steel and aluminum,namely in the nose .

[stefanbuss]

Maybe an aircraft in storage for the last 90somefink years isn't too comparable wrt the amount of rust and/or corrosion, compared with the timeframe the aircraft is going to be shown in (how long in use? Some weeks or some months, but definitely not YEARS).

S.

[ALBATROS1234]

pretty sure they were primed in a red oxide type primer. so perhaps if paint chipped you might see a rusty red color.also i agree with gregory as exchanged electrons would theorhetically cause faster oxidation where steel and alum were in contact

[stefanbuss]

pretty sure they were primed in a red oxide type primer

Excuse me, but why are you so sure about that?

S.

[uncletony]

The introduction of copper to the aluminum alloy essentially turns the resulting material into a kind of battery when exposed to water....

Quite small changes to the composition of an alloy can have a marked influence on the SCC behavior. For example The figure shown here the effect of copper content on the crack growth rate of a series of Al-Cu-Mg alloys. Some care needs to be exercised in interpreting this graph. The change in copper concentration of the alloy will have a marked effect on the corrosion behavior of the alloy (since the copper-containing precipitates are active cathodic sites), but it will also modify the mechanical properties of the alloy and its response to heat treatment. Consequently, it would probably be possible to change the relative orders of the curves by using different heat treatments.

http://corrosion-doctors.org/MatSelect/corraluminalloys.htm

[Michael Scarborough]

Many thanks, gents. Helpful and also fascinating info about corrosion, aluminum/steel combos, cathodic sitesetc.

If I decide to proceed with this build resurrection, I would show the plane as well used but still in flying condition. (Stefan, I only used that photo to indicate what I assumed were specifically the steel portions of the fuselage, not the condition in which I would show the model.)

The WnW instruction book has some great photos of surviving aircraft in Berlin and Canada and points out the red oxide primer. (What I mistakenly assumed was a "haze of rust" in my initial post.)

George, thanks for the info on Operation Michael. Interesting stuff. As far as copper oxidizing to green, aka verdigris, that takes a long time. I have down spouts that I put in at least five years ago and they are still just a dull brown color. I think Justin has hit it on the head with the paint sticking, or not, to the corrugated areas. Any raised area on anything is bound to lose its covering, simply by contact. I would think the areas of the wings around the cockpit would really be bare on the raised portions of the corrugated. Many interesting possibilities.

Thanks, all.

Cheers from NYC,
Michael

[stefanbuss]

Michael,

ok, the "haze of rust" is red oxide primer instead. I was not aware of that. You never stop to learn. One of the reasons why I'm glad being a member of this forum.


Stefan

[ALBATROS1234]

because i recall seeing photos with the engine compartment open and the inside painted in red oxide primer. i may be wrong but this is what i remember from studying photos of the one in canada.

[ALBATROS1234]

damn, i guess this was already adressed. this is what i get for reading one post then responding. sorry. i thought i remembered red primer.

[Michael Scarborough]

Well..you remembered right, Pardner....