Date: Wed, 17 Mar 2010 11:50:29 -0500
Reply-To: Tom Hargrave <thargrav@HIWAAY.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Tom Hargrave <thargrav@HIWAAY.NET>
Subject: Re: Cause of the white corrosion deposit around a battery?
In-Reply-To: <20100317095436.73N51.740330.imail@eastrmwml46>
Content-Type: text/plain; charset="utf-8"
Well, yes and no. The off-gas from the battery only contributes to the problem. It also doesn't help that the wires are copper, today's terminals are zinc plated steel and the posts are lead - a dissimilar metals mix just waiting for an excuse to corrode.
Iron & steel may rust red but not in this case. The steel parts are zinc plated & only when the zinc has corroded through does the steel rust & the rust will be brown, not red. Also lead does not turn red unless you are talking about Lead tetroxide which is red but is not what's growing on your battery terminal. What's growing on your battery terminal is caused by corrosion.
If you really want to get rid of the corrosion go find some copper battery terminals with copper nuts & bolts. Then you will be down to two metals, copper & lead. The copper, being less noble than the lead will oxidize, but copper reacts differently than lead & zinc & steel. The copper surface will turn black then it will stop oxidizing & still being less noble than lead, the copper will continue protecting the lead post. This is also the reason the wires in your wiring harness don't corrode away.
Tom
www.kegkits.com
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of Dave Mcneely
Sent: Wednesday, March 17, 2010 8:55 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Cause of the white corrosion deposit around a battery?
to more completely answer the question, I believe the deposit is metal sulfate produced when sulfate condensate from the battery comes in contact with metal. Either grease or oil will prevent it. If you want to get fancy, most battery vendors sell little felt circles impregnated with a substance that blocks the corrosion from developing. Just slip the disc over the post and tighten down the clamp. They come in red for the positive post, green for the negative, and they work. If you do use oil or grease, remember to tighten the clamp down before greasing the post, of course. There is also a special material sold in a squirt can. It coats the terminals with a purplish plastic like substance that also blocks condensate and air from the terminals but in no way prevents clamp removal.
So far as only the positive post corroding, I believe the sulfate can condense on any surfaces in the vicinity of the battery. In extreme cases, the entire support system for the battery will fail. If the corrosion were from oxygen rather than sulfate, then on steel parts, the substance would be rust red. Now, eventually such parts do rust, if the sulfate corrosion doesn't get them first.
In the simple case, perhaps the lead post itself is corroded with a simple lead oxide, but when the corrosion is over other parts, it is metal sulfate.
DMc
---- Tom Hargrave <thargrav@HIWAAY.NET> wrote:
> It's corrosion and should only be on the positive terminal.
>
> Sometimes you have a leaky seal around a post but this is rare these days.
> More often the corrosion is because the + side of the battery attracts
> oxygen ions from the air and the oxygen interacts with the metal,
> causing the corrosion.
>
> There are a lot of "fixes" you can buy but the best one is to put a
> drop of oil on the terminal every time you check your oil. The oil
> will spread out into a thin film & will protect the terminal from corrosion.
>
> Some people put grease on the terminals. Grease will also work but you
> need to make sure to cover the entire terminal, even the bottom edge
> of the clamp. If you don't then any exposed metal will corrode.
>
> Tom
> www.kegkits.com
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On
> Behalf Of Don Hanson
> Sent: Wednesday, March 17, 2010 12:04 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Cause of the white corrosion deposit around a battery?
>
> What makes the powdery white or gray deposits on some of the metal
> parts around the van batteries? Actually my Vanagon stays pretty free
> of the deposit, but we inherited a 2.5 Subaru Forester that gets it
> bad. We stored it down in Californa during the summer and use it as a
> vacation car. We opened it, around Xmas time to find the
> battery(disconnected but fully
> charged) was covered with a whitish powdery deposits, heaviest on the
> hold-down ring and the clamps, but also under the batt on the tray. I
> bought another new battery...and cleaned everything up with baking
> soda, like a good little car guy before installing that one...
>
> We brought it back to the NW...(shhhh...I'm hoping to finesse it
> (the
> motor) from my wife, eventually..for use in a ....) and I just
> noticed that the hold-down clamps and the retaining ring is again
> almost pure white with a fine powdery substance...Both my Ford Diesel
> trucks do the same thing, but to a lesser degree.
>
> What the heck is this stuff and how do you prevent it forming?
>
> Don Hanson
