best way to remove HCl from your trunk
 

Hi everyone,

I have a 99 that I bought from a crazy old lady. Her brilliant husband was a hack mechanic. Which brings us to my problem: the dude installed a lead acid battery in the trunk. I haven't really paid much attention to the trunk because I've been playing catch up with maintenance and trying to get it track ready. So the other day, I sneak a peek at the battery and realize the battery cubby is filled with battery acid and is starting to rust. Since most of you are engineers, have big kid degrees, or are chemically inclined: what's the best way to neutralize the acid? Fill it with a solution of water and baking soda and sponge it out? Pour lye right on it? Pee on it? I just want to get rid of the acid, sand off the rust, then spray it with whatever I have lying around and never have to deal with it again.

Thanks guys.

I use baking soda to neutralize acid at my studio so I'll suggest that. Be aware that it's going to foam up like a 3rd grade volcano on steroids. Buy more than you think you'll need and be ready to hit it with a water/baking soda mix until there is NO bubbling/foaming activity left at all. Then wire wheel anything that's rusty and then brush on some "Ospho" to kill the remaining rust. Let it dry overnight and paint it.

For reference, I just did this today and it took a box of baking soda to neutralize about a tablespoon of muriatic acid (essentially weak hydrochloric acid).

Holy eff. I don't think my car will hold that much baking soda in one grocery run. Any thoughts on lye? Maybe a shit ton of crushed up tums? Are you sure pee won't work?

My agm battery is coming in Wednesday. I'm getting antsy.

The nice thing about baking soda is that you just pile it in there and don't worry about precise quantities. Put in too much lye and once you counteract the acid you've now got a corrosive base in there instead.

The photos aren't very clear -- is there really an inch or more deep puddle of battery acid in there? If so, I'd be tempted to drill a hole and let it drain out through that before using the baking soda. Easy to plug the hole afterwards.

--Ian

Your trunk looks like it was previously used as a meth lab.

I'd get a syringe and remove as much of that stuff as you can first.

You guys think I can bag this stuff up and sell it to crack heads? The pictures were from my cell cam so they look like poop. The stuff that's left over is just the stuff that precipitated out of solution. It's just dry powder with a ring of rust on top. I'll probably wipe everything out or let the neighbor's kids play with it then use a baking soda solution on the rest then use the rust remover attachment on my dremel. Now will it be safe to put the agm battery in after 24 hours of letting the spray paint dry?

Baking soda would be the safest thing you could use. As stated it is going to produce quite a bit of bubbles but it is the safest way to neutralize the Hydrochloric Acid present. Would stay away from lye as you would be looking a corrosive alkaline solution then. Also, don't use ammonium based material to get the job done. Depending on how concentrated the acid is and how much there is, expect as stated before to use quite a bit of baking soda. After neutralized, drain everything and rinse with tap water. Dry throughly and get to cleaning up the rust. Best of luck.

Credentials: Chemist

The deed is done. It took 5-1lb boxes of baking soda. Took forever and a day for it to stop sizzling. In other news, mazda conveniently placed a plug in the body where the battery resides. After giving it a few taps with the back of a screw driver I drained the (hopefully) neutral solution, dried it off, busted out my dremel and attacked the rust as best as I could. So if anyone is trying to save a few bucks by running a straight lead acid battery, don't. Unless you're selling the car to someone like me.

Glad you got it worked out. And as long as the mess was not foaming anymore you were neutral.