# Why does a car battery posts form white acid dust?



## joeeye

Can anybody add more info to what I remember?

I use to work on cars for many years, I remember hearing that if a car battery starts to form that white acid dust on the terminal posts the battery was no good. 

But now I'm seeing this happen to fairly new battery's.

So now I'm trying to find more information about it, I came across an article I believe was saying as the car is running and the battery charges in the car by the alternator the gas is released and floats its way to the cables where it settles and soon turns to that dusty white acid we all know of.

But I still say this should not happen.


----------



## carsey

The battery does get charged by an alternator in the car when the engine is running.

I have no idea as to what the white dust may be. Maybe it could be oxidization or some of the acid leaking onto the terminals.


----------



## 8210GUY

Likewise I couldn't say definitively what the corrosion is and why it happens, but it is acid related I remember that much, but here's a tip to stop it, or at least minimise it, get some petroleum jelly (Vaseline to most) and cover the terminals with it including any metal from the leads, that should make all the difference for you.


----------



## joeeye

No, don't put petroleum jelly, it heats up and in time will seep between the post and cable then your car won't start.

They make a special spray paint type of material in a aerosol can that you spray on the cable and post when new or when cleaned, there also is another type of special grease for covering the posts and cable, but still don't trust that stuff because it still did the same thing to me breaking the contact between the post and cable in time, I've experienced in time there is never anything other that paint that helps.


----------



## Midnight Tech

It is simple corrosion from the acid fumes...I glue a couple pennies about an inch from the terminals to serve as a sacrificial surface to corrode upon...pennies corrode terminals don't!


----------



## 8210GUY

joeeye said:


> No, don't put petroleum jelly, it heats up and in time will seep between the post and cable then your car won't start.


Really ? well shows how things have moved on these days then, it was standard practise when I last knew about it and had to do it, I know if you get your battery fitted at a garage these days they use the stuff you mention, didn't know it was in the stores though.

You have to be careful using currency depending on the laws of your country, I believe anything like that would be classified as defacing the Queens head and get you in trouble.


----------



## A-Nick4me

8210GUY said:


> You have to be careful using currency depending on the laws of your country, I believe anything like that would be classified as defacing the Queens head and get you in trouble.


I wonder how a country would police something like that?


----------



## carsey

Maybe I shud get a blowtorch and try and melt the coin.

You certainly dont hear about grasscutters getting wrong for shredding the coins up


----------



## 8210GUY

Well logistically they wouldn't really, it would be a case if you were caught for something else and they wanted to be a jobs worth and come across it in the process they could use it against you, a grass cutter would not be an issue as it would be an uncontrollable accident, but as a kid I used to get a reel of caps and place it between 2 coins and stamp on it in the local subway, talk about an echo lol, but if I were caught I could of been in trouble apparently because it was a deliberate defacing, but as to whether anyone would ever bother and follow it all the way is another issue, but felt it worth a mention incase.


----------



## curious99

the batteries that have corrosion buildup all have the same prob:upset: em,yes it is the acid ,but it usually is because the case is not sealed around the terminals.this is a common problem and cheaply corrected.install battery post pads sold wherever batteries are sold,even Walmart.if a battery is leaking acid from the caps,it usually is overcharging,and you should have charging system checked out.overcharging will prematurely kill batt.:upset:


----------

