Corrosion on Optima battery terminals

[Mark Roth]

Noticed that I have corrosion on the negative terminal of both the 6v and 12v batteries (two cars). I also have one of the twist knob battery disconnectors on both terminals. The batteries are old and are to be replaced but I have never seen this before. Is it the metal in the disconnectors or just Optimas that are old and starting to leak gas? Or both? Thanks.

[Jeffrey Leeds]

Mark, I had a similar problem a few years ago but with a different battery. But what we do have in common is the battery connector - yours sounds the same as the one I had then. I tossed mine and haven't had the problem since.

[Norm Miller]

Likely Gulf coast air & humidity.
Haven't seen it before. But yes with lead acid batteries.

Norm

[Mark Roth]

I should have clarified that I have seen this corrosion before but never with the Optimas. I always thought that it was the hydrogen gas escaping from the vents on the battery that caused it. I was curious if maybe the Optimas were starting to leak gas. Might be electrolysis from the different metals in the disconnectors. Since I rarely, if ever, used the disconnectors, I'm going to trash them.

[Frazer Carless]

I,ve seen this often where an isolator is used. those screw down ones are a bit iffy especially with 6 volt - I had hard starting from cold with my car, plus lots of electrolysis on the neg terminal, for years until I eventually realised that I was getting poor earth through the isolator, scrapped it and never a problem since! Frazer

[Dave Wildrick]

I had those cutoff switches (with green knob) on both C coupes and 6V Optimas in both. When I had to leave my 64C outside the garage in the Houston summer air for about 2 months (under a car cover), corrosion developed on the metal contacts of the switch itself, but not on the Optima terminals. The corrosion/oxidation was enough to keep the starter from operating. No problem after I removed the switch.

On the 65 C coupe, which has always been garaged, I have had no similar problem with the switch, and it is still working; also, no corrosion on the Optima battery posts.

[Mark Roth]

Both cars are garaged. The green knob switches are going in the trash. Don't use them anyway and they come lose.

[Larry Coreth]

Guys,

It was standard practice and still should be to put a thin coating of grease (it does not matter what kind of grease nor does the fact that grease is non-conduct matter, experimentally verified) on the battery posts as well as the inside of the connecting terminals. Further if you want avoid the white fuzz on the outside of the terminals; put a thin (very) coating on the outside of the terminals too.

One more thing, it is also wise to clean the posts and terminal insides prior to greasing with a battery post & terminal brush available from many battery retailers. In the “good ol’ days” they were give away items (swag?)

For those of a curious nature, on lead-acid batteries the acid (H2SO4) vapors are responsible for terminal corrosion. On sealed or Optima batteries I’m not sure of the root cause of this corrosion but the grease should minimize its formation.