"Help! eg of Magnetic bases causing corrosion. " Topic

Last year, I glued thin magnetic sheet under the bases of many of my 1/300 Ros & Heroics tanks. In my last game, I used units of about 4 or 5 tanks on 6cm by 4cm thin metal rectangular bases (made from thin soda can metal glued on card). The magnetism meant that the tanks stuck nicely onto the metal unit bases. For the next 5 months, I happened to leave the tank units on the metal bases, stored in an airtight plastic tupperware container. When I opened the box recently, I was horrified to see brown corrosion on the tanks. To be specific, not on the soft metal of the castings, but rather, on harder metal bits where I had used pins to replace gun barrells or bits of metal staple to make aerials or flag pennant poles. So, the magnetic pulling together of the magnetic sheet and metal sheet caused a corrosive micro environment. Incidently, the corrosion came from within -breaking out through the paint and strong varnish seal. Gave the appearance of ugly little brown grain/extrusion on the hard metal parts. Simple solution I guess: don't leave figures/ models with magnetic bases on a metal surface for a long period of time -that is, if you have added hard metal improvements. Remove the figs/models back into their boxes after each game, and store the metal sheets far away.

Any comments on the above are welcome -since I'm not a chemist!
My related question concerns my 15mm figures: I recently started a system of lining the bottoms of my figure boxes with magnetic sheet glued down. I also have magnetic sheet under the bases of my 15mm figures themselves. The idea was that the magnet to magnet pull would mean that my figures could be safely transported in those boxes without sliding around. My concern is: I have replaced nearly all spears and flagpoles on my figs with stronger ones made from pins. Am I likely after a few months to get the same corrosion problem on the hard metal bits as I did with the WWII magnetic sheet to metal base environment described above?
Any help /advice from anyone with relevant expertise or experience using magnetic to magnetic, or magnetic to metal, basing would be greatly appreciated! A trawl of internet showed me only that there can be a connection between magnetism and corrosion – but apparently it can also retard corrosion! Help and thoughts appreciated!

I wonder if there was humidity in the airtight box. You might want to consider either allowing airflow into your storage, or else using desiccant packs. That could be the problem, since inert metal-on-inert metal contact does not cause problems. There has to be something else to cause a chemical reaction. Or perhaps the soda cans were not completely clean and the acid found in soda caused the reaction.

Magnetism doesn't cause rust (which is what you seem to describe). Rust can only occur if there is water and oxygen present hence there must have been both in the container when it was sealed.

The problem could be a galvanic reaction between the metal alloy in the model and the coating on the pins or staples. A number of metals can be a problem with iron present and can accelerate corrosion of the iron.

The connection between magnetism and corrosion is that a strong field (far stronger than that you would get even quite close to a magnetic base) can increase the current flow in a galvanic reaction and speed up the process.

Solution is to put one of those little packs of Silica Gel in the box next time.

What Gildas said.

this is why we paint things: ti protect them from the elemets.
scrape off the rust and use a clear coat
:(

Use brass rod not steel pins or staples.

--
Martin Stephenson
The Waving Flag | Twitter | eBay

I have thousands of figures mounted on steel and stored in magnet lined boxes. I've been using this system for close to 10 years and every figure looks as good today as when I put them in the boxes, including some with metal flag poles replacing the white metal ones, some vehicles with metal and plastic additions.

The boxes I use are not airtight and made of corrugated so may "breathe" more, and they are usually stored in a dry environment.

LOL from your moniker Durban Gamer, you live in Durbs 'down by the sea' :) everything in Durban rusts haha even the people :+).
Solution is to use galvanised sheet metal and the same for pins etc. The humidity and those earth magnets help speed up the whole metal to rust thing :(.
Solution to barrels and flags in those scales, is look around stores for thick bristle brooms (plastic flexible will take acrylic paint and generally robust enough for thick fingered gamers like me) and if it must be metal look through the metal scrubbing brushes ( invest in one of those pincer cutters too) these seem to be protected from elements as they are used in watery environments.
Hope that helps BTW what rules you using for your 6 mm and what you do in 15 mm
Cheers from the Midlands.

As I understand it you are saying you're getting rust forming in metal that has been painted. If that's the case it's a problem with poor quality metal that still contains too much moisture. Sounds daft that steel can still contain moisture but it's true. Magnetic sheet etc has nothing to do with it. The paint is sealing it from external causes of corrosion but of course the paint can't protect it from the moisture within.

I'd use brass wire instead, being soft it's easy to work with for model making purposes.

You may not believe this, but I know a guy that found a unique material for radio antennas. He uses…get this…whiskers from his cat.

"Here, kitty kitty".

I use fishing line for my antennas. 25lb test is a bit large, but it's plenty strong and flexible.

Tooth brush bristles, 10,000 in every brush. Work great for
aerials or flag pennant poles.

I have 5,000+ magnetically-based minis with steel spears, many stored for over a decade and I've not experienced any corrosion. I fear that danp must have somehow got into your box before it was sealed, as another poster has suggested, and worked away at them.

Thanks to everyone for your thoughtful and helpful responses. I'm encouraged to see that magnetic basing per se is not a rust causer. I'm inclined to conclude in light of the input that the cooldrink cans had acid moisture which created a corrosion climate in the tightly sealed box over 5 months in very hot, humid weather. The protruding hard metal bits became like battery terminals on the magnetic sheet to cooldrink can bases.
Good news is that rust not too bad yet. Fine stone hobby drill cleanup and a coat of gloss varnish will restore the barrels and aerials/pennant poles. Of course, no more long-term storage on cooldrink can unit bases for my beloved models!

Too bad the models are the small ones. Some corrosion on a 1:28 scale tank might look pretty interesting.

very hot, humid weather

That's your primary problem.

no more long-term storage on cooldrink can unit bases

You could still use them, just wash, rinse, and dry them well using a degreaser or detergent. The issue is more likely the humidity. You should put desiccant packs in your storage, and use moisture absorbers like DampRid or an electric dehumidifier to reduce the overall amount of moisture in the room's air. Aim for 50% RH or lower, and don't use any air-tight storage.