Chemkote? Corrosion inside old M@g ...

[hank]

One of my old MagD lights has a patch deep inside where an alkaline must have leaked long ago, and now the area's going dusty and pitting.

No idea when it happened, haven't noticed any problem, or had a battery leak, but something started eating it.

Either there was something corrosive left in there that apparently never got clean enough or there's enough outgassing from the batteries inside to make a clean but bare metal spot corrode further.

What's the best way to clean it out? (I've just swabbed it out with water and let it drain dry). Then to recoat the inside? Ordinary aluminum-grade primer paint, I'd guess, but I'm not sure if there's chemical corrosion in the pitted areas that I need to do more about.

I am guessing these are just black-painted metal, nothing special, I can see the edges of the paint peeling a bit where the corrosion happened.

 

[Lightguy27]

Mag Lights are aluminum actually.

 

[JamisonM]

If it is really some kind of corrosive substance, the best thing I know of to do is neutralize it and to do that I've found that ammonia works well; least it does on my knives. You can also use windex, but it pretty much the same thing, though, its been colored and diluted, but in a since that's actually a good think seeing as this stuff can know you out.

 

[hank]

> aluminum

Yes, that's why I asked if aluminum primer paint was likely to be the best thing to use inside the tube. Or does anyone know a chemical/paint/treatment that's better for preventing corrosion?

I'm guessing these are just black painted metal [aluminum] (not anodized or treated with something as they come from the M@g factory) -- but that's why I'm asking, hoping someone knows.

I know Arc has used something called ChemKote, a greenish-yellow coating, to prevent this kind of problem inside battery tubes, but I don't know of any source of something like that, never needed it before.

As to what could be in there -- hmmm, just had a scary thought. I'd been worrying just about alkaline battery chemistry.

But some of the alkalines do or did contain mercury.

Aluminum's odd stuff -- get a little mercury on aluminum, and it will slowly degrade away permanently because the oxide coat aluminum usually forms is prevented. And some batteries do or did contain mercury, come to think of it, so that would be a worst case guess.

I know airframe manufacturers are really careful because something like a mercury thermometer broken in an airplane can badly degrade the structure over time.

So if this is mercury poisoning, I dunno what would solve the problem.
Maybe some tin powder to make an amalgam. Sheesh.

 

[hank]

Here's a pointer on why aluminum gets corroded by mercury.
http://www.popsci.com/popsci/how20/09550e0796b84010vgnvcm1000004eecbccdrcrd.html
Looking further inside the M@g, I'm guessing that's what happened, one of the older alkalines with significant mercury may have leaked. The 'fluffy' aluminum compound and pitting looks like the illustrations. Now, what to do ... if anything. Maybe just painting over it with a good primer will block the oxygen out, but I don't know.

 

[willrx]

Hank,
Keep us posted on this one. I have several old Mags and hope none are secretly disintegrating.

 

[hank]

If anyone does know where the flashlight manufacturers get their ChemKote, or anything like it --- I'd rather try that than just painting the inside.

On the -- pure speculation, I remind you!-- chance it's a bit of mercury ratehr than just alkaline battery chemicals of some other kind causing the problem,
I can get powdered zinc, and rub that into the corroding area -- if there's a trace of mercury that'd grab it and make an amalgam.

The battery cleaned up fine -- the black paint from the inside of the M@g tube had actually been pressed onto the battery by the white gunk growing out of the metal.

Ick.

Anyone know of thin plastic tubing about the right size to 'sleeve' D-cells before sliding them into the flashlight?

I wonder if putting a dessicant pack into the tailcap (in the empty space where an incandescent bulb would go) would reduce corrosion any. Don't know enough chemistry to know what could have been the cause or how to get rid of it.

Feh.

 

[scott.cr]

This is a $17 flashlight. If you're just dying to put $187 worth of work into it, cut it off and rethread. ;-)

 

[hank]

Chemkote is that expensive? What's your source?

Or are you over-valuing my time? I'm just going to clean out the inside of the tube and paint it. I'm asking advice about "with what" before messing with it.

I can do it with my feet up and the TV on, so won't charge myself that rate.