Two years ago, I bought a brand new 1GA positive battery cable from JIm Carter. I also bought the negative strap. I installed the pole shoes properly to the battery on my 1939 car, added vaseline on both pole shoes after installation and put on a isolating rubber around the +pole unit. Everything according to «the book».
Now I found the same +pole completely corroded, I removed a lump of white corrosion. The pole shoe was really stuck and after removal, I find that the lower third of the pole shoe is almost weathered. I had not expected this. The pole shoe need to be changed.
On the other side, the negative pole shoe is still fine as new.
How could this happen? The battery on the 1939 is mounted under the floor at the passenger side.

from what i understand one of the causes of corrosion on the positive terminal is from overcharging.
do you leave it connected all the time, and on a charger or maintainer.

I had some charging problems a year ago, I was charging a lot at that time, but never for a long period continously. After I changed the regulator. Last year I have not charged at all.

I would check if the charger was going into maintenance mode properly after the battery was charged. I would also check that the car is not overcharging the battery while you drive.

The cause of the corrosion is simple. Your battery is venting corrosive gasses. The reason(s) it's venting corrosive gasses can be several. The most common are an old battery nearing the end of it's life and overcharging.

Hei Sundfar

Some batteries seep a small amount of acid around the posts.
If you added vaseline AFTER you installed the cable clamp, you only protected the TOP of the clamp and battery post, and that's why the BOTTOM 1/3 is corroded.
This is why I always grease the battery post and cable BEFORE I install the clamp.

Then when you tighten the clamp, it squeezes out the excess grease and makes a solid connection and leaves all open spaces filled with grease, protecting the top AND bottom of the connection.

This has worked for me for many decades.
I hope it works for you too. :-)

Hello Stoveblt, thank you for this tips.
At the bottom of the pole, i first added a greased felt, then a plastic ring, before installing the pole shoe. There is used a lot of grease. I find it more likely that the gases from the battery is the reason, because it is not much ventilation and fresh air between the battery and the floor cover plate.

Tiny
I like your theory about gases. Battery is 5 years old, it should not be to old. Previous battery in same car lasted more than 10 years.

Hei igjen

I've found that I need grease IN the connection.
That's why i grease the post, then set the clamp down over it, so all internal contact surfaces are covered with grease.

Not theory. Corrosion is caused by offgassing. Google it. I've had modern batteries last ten years and I've had them fail after four years. Five years would not be surprising.

Not all battery cases fully seal around the posts and the acidic gases leak past and can penetrate through the grease and a lot of the other so called protectants. If I find that situation I clean the terminals with bicarb soda in hot water more often.
Tony