"POTENTIAL PROBLEM WITH ALUMINIUM CORROSION!" Topic

From Thaddeus Blanchette'ssite…

Folks, I have just discovered a very serious problem with O8 miniatures. It is not Marcin's fault and it is not a show-stopper, by any means, but beware! A pinch of prevention is worth a pound of cure. So… Last year, I bought an unpainted MDF filing cabinet thingie to store my figs in. I had a bunch of white-metal figs in it for the better part of a year without any problems at all. Then, in February, I moved my O8 sci-fi stuff in. Disaster!

Unpacking some of the figs last week, I noticed that some of them had grown a thick, white fluffy crust, looking something like mold or maybe mineral salts. About 1/3rd of my figs had caught this "disease" (none of the recently painted sci-fi stuff yet, thank heavens!) It could be easily scrubbed off with a brush, but the paint job underneath looked flaked and pitted. This has mainly hit my oldfigs and some of the newer paint jobs where I stopped mid-paint, without varnishing. Some of the figs are so encrusted they'll have to be stripped and repainted. It has not hit:

1) White metal or plastic figs, even those painted with the same paints.

2) Heavily painted and varnished O8 figs.

I very much doubt it is a fungus, then, even though it looks like it. It has to be something to do with O8's aluminium alloy. It certainly isn't lead rot (although it looks something like it) because O8's figs contain no lead. It also can't be something to do with a more general long-term degradation of O8's alloy because even though my old figs got heavily infected, the newest, somewhat unpainted figs also got hit.

Meanwhile, almost unpainted/unfinished O8 figs in my old plastic and pine wood boxes have been doing just fine. I stumbled around on the interent yesterday, and I have a working hypothesis re: what may be going on here… Apparently, certain forms of high-pressure wood treatment, which are most commonly used in MDF, contain large amounts of copper, which can outgas up to years after manufacture. Copper reacts poorly with aluminium, causing it to corrode.

I've noticed that the "infection" seems to occur most commonly in the drawers with MDF dividers, towards the bottom of the cabinet and in the figs that are closest to any uncovered MDF. The figs in the "open" and undivided drawers near the top, clustered in the middle, show no signs of corrosion at all. Also, it's the old figs (with lots of pin-hole dings in their paintjobs) and the newer, partially-painted and unvarnished stuff that's getting hit. My ACW figs, which have spent almost a year in a divided drawer in the bottom of the shelving unit show no signs of infection yet: they were, however, practically drowned in brush-on varnish.

I am thus moving ALL my O8 stuff out of the MDF drawers and back into the plastic containers.

A word to the wise: three months in storage was all it took, so this is a fast-acting problem. I have been able to save some figs by scraping off the corrosion with an exacto knife and repainting. I will be anxious to see if this holds up.

I'm hoping the corrosion doesn't spread after scraping and repainting! So a word to the wise: store your O8 figs in plastic or untreated wood! If anyone else has had this trouble, I'm anxious to hear about it.

Abraços,
Thaddeus

Aluminum figures?

Yes, Oddzial Osmy uses an alloy of aluminum and zinc, both of which corrode in similar environments. I wonder if alloying the two makes them even more prone to rapid corrosion?

Thanks for the heads-up, Dave (and Thaddeus). Three months, that is *really* fast for that level of corrosion to occur.

They are zinc with aluminium (plus other stuff). You probably have a lot of things made from it at home, but you just don't know it.
I've never seen such things happening – maybe some specific circumstances occurred. We will investigate it.

Marcin
Oddzial Osmy

Aluminum figures?

No, aluminium.

;)

"unpainted MDF filing cabinet" mdf gives off formaldehyde which will cause the type of bloom and corrosion you mention. It will build up in concentration in an enclosed atmosphere. Storage of any metallic object (silverware, coins, medals etc) should be done in an acid-free environment. Lack of varnish probably helped, and maybe zinc and aluminium are more susceptible.
Incidently many late WW2 german medals were made of zinc based metals and will happily turn to dust if kept in a draw.

I once had along argument with an eminent engineering academic who was convinced that Aluminium would not corrode…….

Hah! David, he must have never taken a materials engineering class.

"Aluminium corrosion resistance is very good in untreated aluminium. Untreated aluminium has very good corrosion resistance in most environments. This is primarily because aluminium spontaneously forms a thin but effective oxide layer that prevents further oxidation.

Aluminium oxide is impermeable and, unlike the oxide layers on many other metals, it adheres strongly to the parent metal. If damaged mechanically, aluminium's oxide layer repairs itself immediately."
link

Of course, I don't know if the same is true of an aluminium/zinc alloy …

I had a similar issue – but with lead figures.
I had purchased some painted Russian Napoleonic 28's on eBay from a seller in Hawaii.
I stored them in cardboard boxes.
I pulled them out for a game, and noticed a slight encrustation, on one or two of the figures, but thought little of it.
The next time I pulled them out, the mold, or whatever it was had spread, affecting all the Russian cavalry, and jumping from that unit to other units that I had painted myself – so not purchased from Hawaii.
Alarmed, I dug out the Russian infantry that had come from Hawaii, and they too had the encrustation.

I brushed them with an old toothbrush – helped, but not much.
So I sprayed them with water and bleach, assuming that the encrustation was a form of mold.
That helped a little more, but some of the figures are now less than sterling.

The cardboard storage containers had been advertised as suitable for archival use – but something came with the figures from Hawaii, and got the right conditions it needed for growth.

I don't know if the Hawaiian figures were varnished, but I do know the figures I painted that were affected, were not varnished.

Not only have I taken a class in Materials Engineering, I've actually got a degree and 25 years of experience in the field. Without actually examining the figures, I'd say it sounds very much like Zinc corrosion. Aluminum is indeed very resistant to atmospheric corrosion but there is probably not enough in the alloy to form a good oxide layer. Certainly outgassing of Formaldehyde will accelerate the corrosion process. ( Cu won't outgas, it not volatile.). Best solution is to seal the figures quickly or to use desiccant bags for storage.

Many spices react with aluminum. If you use something for a base coating that may have been "spiced" this might also cause a reaction.

Pure aluminum is highly resistant but most alloys are highly susceptible to corrosion. That is why the alloy sheets used for aircraft have a layer of pure aluminum cladding and any cut edges have to be chemically treated. I always laugh at the notion that aluminum won't corrode because I spent 20 years repairing and replacing corroded aircraft structure.

I have a lot of O8 stuff (mostly unpainted as always) and I haven't seen that happen, although I have learned not to soak them in vinegar as part of the prep process.

Hm. Very odd indeed. And naturally, as a big time O8 guy myself, somewhat concerning. But I have never had such a problem.

I'd rule out anything organic as zinc tends to present a hostile microbial environment. Copper and zinc do form electrical potential in acid, though that might just make them reject, not necessarily oxidize.

This sounds more to the point: link

Given drawers ( closed environments) and the fact that Thaddeus lives in Brazil (consistent high humidity), I think we might have a winner.

Zinc is typically a very stable metal, though. Very odd.

A layer of pacific cloth might help avoid this kind of corrosion, perhaps a silica packet to cut moisture.

Have a very large amount of 08 as well, so following this thread with interest. I had purchased MDF hexes to use as 1/600 terrain bases, but the contact between based minis and flocked terrain should not be an issue.

Good to know about zinc corrosion however, appreciate the heads-up.

BTW, does anyone know how long a silica packet lasts before needing replacement? I live in the desert southwest, so moisture is generally not an issue, but would be good to know in case of a future move to a more humid climate.

They last for years. I've actually never had one "wear out," that I know of. They make ones that contain a reagent that changes color when the gel is moist, and then you heat it to "recharge" it.

According to our maid, if you don't have sikicon gel, you can use plain old laundry soap (in flakes, of coirse) to suck out moisture.

She swears by it.

I'm with Rich on this one, no chance this is the Al, must be the Zn but, whatever it is, I strongly suspect local conditions are more the issue than it being a general risk.

I store almost all my painted OO stuff in metal drawers with MDF inserts and have not noticed any sort of problem with either painted or unpainted figures. I keep meaning to put silica gel in all the drawers but I haven't had any in those.

Well, if it were just local conditions – and not local conditions + MDF – there would be corrosion in the figs stored elsewhere. As is, this only shows up in the figs stored in the MDF shelving unit.

There are figs stored in an old wooden chest of drawers that have been there for years and show no corrosion.

Also, RdJ isn't ridiculously humid, especially during the last year. Given that this happened in the space of three months during a drought…

I meant that the situation you have them in – whatever is present in whatever combination plus temperature, humidity, ventilation etc. etc. From the evidence above it seems that others have the OO figures plus MDF combination without any problems.

I also have no doubt that MDF isn't a fixed composition product and that the varieties will outgas different amounts of whatever is causing the problem.

The same issue has been discussed with relation to 'lead rot' and conditions seemingly identical produce no problems for one user and rampant rot for another. It never gets clear what the explanation is in detail and I know of no real attempts to find the true cause(s).

Ahn. "Local" for extremely local values of local.

Yes, it does seem that some of the drawers are more toxic than others.

If aluminum doesn't corrode why is it possible to anodize it?

I wonder if the mold release compound was involved.

I have some rather old brass figures from the late 1800's early 1900s. They are still kicking strong. :-)

All my lead from the early days late 70s early 80s still look good.

I had the same issue with 15mm scifi figures from The Scene, painted and varnished, based on MDF bases, and they looked corroded last time I looked. My other figures stored in the same place were fine.

Aluminium does corrode, it goes to a white powder sometimes quite sticky, well my land rover does anyway ;-)