View Full Version : Battery terminal corrosion

03-25-2012, 08:34 AM
What causes the positive terminal on an automotive battery to grow the green fuzz that destroys the battery cable?

I have four cars. One of them grows the corrosive fuzz and the rest don't. I have cleaned the battery and it comes back. I have used the red spray sealer on it and it comes back. I thought it may be due to a moist hood insulator sheet hanging down and touching the terminal but that's not it.

Is it due to overcharging? Its on a '99 SAAB 9-3. Would replacing the voltage regulator help? I need to figure out if its in the alternator or separate.

03-25-2012, 08:40 AM
I've wondered this as well. Neither of my Cruisers has this problem, but my wife's car grows the green fuzz.

03-25-2012, 09:25 AM
sulfuric acid is corroding the iron and copper. You can use baking soda to neutralize the acid and clean the wires and battery. In a nut shell it's leaking slightly at the terminal (usually overcharging or insufficient venting) or the water vent holes is creeping to the + terminal. Use a baking soda paste and scrub the positive terminal clean and clean the rest of the battery. I then put a slim coat of grease around the terminal base to prevent any leaking, connect the terminal and spray it with permatex battery thingamagig stuff

03-25-2012, 09:41 AM
I have found wd-40 does a pretty good job cleaning it, did that on my camper battery last year and it still hasn't grown back.

03-25-2012, 12:04 PM
I think wes has it right on, i think some batteries leak more around the terminals than others.

I read a long article on why most subaru's grow the green fuz not too long ago, their idea was that it had to do with how the grounds were arranged. I didn't buy it.

03-25-2012, 01:03 PM
Ovecharging can hasten it as would running a flooded battery. It's plain old galvanic corrosion, the rusting of lead and copper in the presence of an electrolyte. An AGM would be less likely because it should not vent normally. I dunno why one car might be more likely than another. Maybe the location of the battery does not dilute and vent the collected gas as well another car. Shrug.

In any case, smear dielectric grease on the terminal after cleaning when you put the cable back on and then smear grease all over the connection after. That does not have to be dielectric grease, I just use excess grease from when I lube the driveshaft. That serves as an additional reminder to service the DS when I start seeing some corrosion on the battery forming.