Took my last drive in the ol' boy today, before storing him in his zippered cocoon for the duration of our Wisconsin winter. I noticed this white "crust" on the positive battery post clamp bolt. I used what was sold as a standard battery post bolt. No irregularities in the charging as indicated by the voltmeter on the dash. No apparent leakage from the top of the battery.

 

Dunno the exact cause Valerie but that doesn't look good!
See here for a list of possible explanations and solutions: https://mechanicbase.com/electric/ba...nal-corrosion/

 

Above link is good. Leakage is most common cause. You need to obviously clean it all off, and then when you reconnect, smear the whole lot with a generous dollop of vaseline. Always used to work for me.

 

Very good information on the link posted by OzXFR. The only thing I don't agree with is the use of sand paper to clean anything that you expect to have good electrical conductivity. If you want to use something abrasive use a scotch bright pad or better yet, use a battery post cleaner. These are available at all auto parts stores. For years I have been using the green and red felt pads for battery posts, also sold at auto parts stores in the battery terminals section.
Bill.

 

Hi Valerie,
What you are seeing is corrosion caused by battery acid fumes leaking from around the battery post. You need to use baking soda and water mixture to nuterlize the acid. Auto parts stores use to sell felt type rings that you placed under the clamp squirt oil on to help stop it. Other ways were to smear the clean post with wheel bearing/suspension grease prior to installing the battery cables. There is a spray that you spray on after cleaning it and the cables were on to seal the air and acid out.

 

What Bob_S said. Don't sand it, flush it with a baking soda solution and wipe the terminals and clamp with a rag. I also use the felt circles around the terminals and they seem to keep everything clean. They're easily found at most "McParts" stores.

 

Thank you all. :-) for the suggestions. I used to use the red/green felt circles, still have a fresh set and will put them on come "de-cocooning". Will also get some bearing grease... would dielectric work at all? And why the bolt only?. No corrosion on the battery post, or cable end, just the bolt.. has to be some sort of chemical / electrical interaction. Will also check the battery voltage while running.

 

The bolt is a different metal than the clamp (I believe steel vs. lead alloy) so the metals are reacting differently. Dielectric grease is fine but not really necessary as you're just trying to protect the metal, not limit stray electrons from moving about. Either way I'd not use it (or any other grease) on the battery post itself or the inside of the clamp as you want as clean a contact there as possible. YMMV but I've found the felt rings themselves are adequate to keep the terminals clean.