# Mercury battery corrosion -- how dangerous?



## Seamus42 (Aug 19, 2018)

Hi all -- new forum member here, in search of some info. I just picked up what appeared to be a pristine Olympus 35 RC, only to realize later that I'd neglected checking the battery compartment. In short, it won't open. And there's also yellowish staining around the battery cover. I'm assuming this means an old mercury battery has burst inside the compartment.

So -- I've heard/read many differing opinions regarding the actual toxicity of mercury in batteries, but at the end of the day, I'm torn about whether to tackle this job. I'd be bummed about losing $30, but more bummed about ingesting/absorbing mercury. Anyone know about the safety of cleaning this corrosion? Any tips?

Thanks!


----------



## tirediron (Aug 19, 2018)

The amount of mercury in a mercury cell (assuming it is one and not something different) is relatively small and unlikely to cause any harm.  Wear rubber gloves and work in a ventilated area (mercury isn't always the nastiest chemical in a mercury battery either).  Work on a plastic or other impermeable surface and once you get in open carefully decant the whole mess into a small pill bottle or other secure container and take to a local battery recycler for safe disposal.

If the threads of the battery compartment are well and truly glued with battery guck, this could be very difficult.  I would recommend going to your local cheap tool store (Harbour Freight, Princess Auto, etc) and buying a screwdriver with a blade somewhat larger than the slot.  Ensure the screwdriver has a square or hex shank and NOT a round one.  The shape the screwdriver blade until it's a custom fit for that slot, ensuring you remove the taper.  Put a couple of drops of penetrating oil around the threads, and use a small wrench to provide extra leverage on the screwdriver if necessary, but DO NOT force it.  Repeated persuasion will win eventually.


----------



## Seamus42 (Aug 19, 2018)

Thank you! That's extremely helpful. I was also wondering about just taking the bottom plate off -- looks easy enough to do. 

Mercuric oxide seems like some really nasty stuff, so I'm glad to hear there isn't much here.


----------



## weepete (Aug 19, 2018)

Don't lick it  that should prevent you from ingesting any.


----------



## Seamus42 (Aug 19, 2018)

weepete said:


> Don't lick it  that should prevent you from ingesting any.



Wise words indeed !  

I already touched it, and it absorbs through skin. But I'm not gonna lose any sleep over it. I imagine that around the time of my childhood in the '70s, people were probably licking them for fun. And most of them are still with us!


----------



## weepete (Aug 19, 2018)

yeah, sorry, I couldn't resist that one!

I knew a few people who told stories of playing with mercury in a sink as kids. The good news is that unbroken skin is pretty bad at absorbing stuff, though it will absorb some. That's why painkilling gel is pretty much a nonsense (it has an absorbion rate of around 5% if I remember correctly). So yeah, prolonged exposure can be bad but something would have to really be unusual for it to cause any serious damage.


----------



## Derrel (Aug 19, 2018)

tirediron said:
			
		

> >SNIP>
> If the threads of the battery compartment are well and truly glued with battery guck, this could be very difficult.  I would recommend going to your local cheap tool store (Harbour Freight, Princess Auto, etc) and buying a screwdriver with a blade somewhat larger than the slot.  Ensure the screwdriver has a square or hex shank and NOT a round one.  The shape the screwdriver blade until it's a custom fit for that slot, ensuring you remove the taper.  Put a couple of drops of penetrating oil around the threads, and use a small wrench to provide extra leverage on the screwdriver if necessary, but DO NOT force it.  Repeated persuasion will win eventually.



I have an alternative way to make the *rounded-edge screwdriver bit* you need; use a Canadian or American five-cent coin, and a pair of quality pliers or Vise Grip pliers...the fit is almost perfect, since most Japan-made cameras were actually designed to use a Japanese coin that was common back in the era. But yes, to the penetrating oil. And yes, the Vise Grip pliers are excellent for leverage, since they can be used in either a vertical or a horizontal direction in relation to the screwdriver bit. If you need to, you can file or grind the coin a very slight bit, if needed, and this is where the Vise Grips serve as a vise! You want the rounded edge though!

The five-cent coin has no taper, and it's a good,thick, stout screwdriver bit! I suppose that there might be other coins that would work as well, such as _perhaps_, the newest, gold-colored, USA $1 coins, the Sacajawea or the US Presidential series mintings.


----------



## tirediron (Aug 19, 2018)

Derrel said:


> The five-cent coin has no taper, and it's a good,thick, stout screwdriver bit! I suppose that there might be other coins that would work as well, such as _perhaps_, the newest, gold-colored, USA $1 coins, the Sacajawea or the US Presidential series mintings.


  Shows you how long it's been since I mucked about with this gear; I totally forgot about the nickel trick.  Yes, go with Derrel's suggestion on this; MUCH easier than customizing a screwdriver.


----------



## compur (Aug 19, 2018)

Seamus42 said:


> I was also wondering about just taking the bottom plate off -- looks easy enough to do.



Yes. If the cover won't open with the nickel trick then you can certainly take the bottom plate off.

Soak the plate in some vinegar (to dissolve the corrosion) for a while and try to open it again. Once open, use vinegar to clean out the battery compartment. Then wipe with rubbing alcohol to remove the vinegar smell and any residue. 

With the bottom off you can also check to see if the corrosion damaged the wire connections to the battery compartment. If so, they will have to be re-soldered for the meter to work.


----------



## jcdeboever (Aug 20, 2018)

I would drill a 2 small holes through the cap and use an adjustable spanner wrench with the pointy ends to take it off.


----------



## Grandpa Ron (Sep 1, 2018)

I would use rubber gloves and work over a new paper to keep the debris contained. 

As kids we used to shine up silver coins and roll the little balls on mercury around the table.

Who knew?


----------

