Lots of Negative Terminal Corrosion

[Max Simmons]

Checking water levels in the 8 D's and found the one battery serving the starter on the Starboard to be heavily corroded on the negative terminal. Positive side looked great. I did clean these last year and added a bus-bar on the negative side to neaten up some wiring that had been bugging me. All connections seemed tight.
Any suggestions to cause or why negative side only?

Thanks

 

[Comodave]

I clean up all the battery connections, tighten them up and then spray them with Boeshield. I don’t seem to have any corrosion issues after doing that.

 

[O C Diver]

Corrosion X is also great for preventing terminal corrosin.

Ted

 

[Bacchus]

I've seen the following before but no idea if it is fact or myth...

"In many cases, it's believed that the corrosion will typically form around the negative terminal, which suggests that*the battery is “undercharging” due to a lack of adequate driving time. Corrosion around the positive terminal is generally believed to be the result of overcharging from the alternator."

 

[tiltrider1]

I've seen the following before but no idea if it is fact or myth...

"In many cases, it's believed that the corrosion will typically form around the negative terminal, which suggests that*the battery is “undercharging” due to a lack of adequate driving time. Corrosion around the positive terminal is generally believed to be the result of overcharging from the alternator."

I have not heard this before, have no idea.

Typically, the corrosion is caused by gasses venting from the battery. Check your vent caps. If any of the vent holes are pointing towards the negative battery post you will have found your answer.

 

[EngNate]

In fact, conditions the same, you will always find the connections and wires on the negative side of a circuit corrode first and most. In AC circuits its the grounded current carrying conductor (neutral). Clean all contact surfaces bright, tighten securely and spray with clear acrylic or urethane, this is the cleanest stuff to use and lasts long. Excessive gassing and water loss may be an issue, and look for any other source of water getting on the connection.

 

[catalinajack]

Checking water levels in the 8 D's and found the one battery serving the starter on the Starboard to be heavily corroded on the negative terminal. Positive side looked great. I did clean these last year and added a bus-bar on the negative side to neaten up some wiring that had been bugging me. All connections seemed tight.

Any suggestions to cause or why negative side only?



Thanks

KoprKote. Doubles as a great anti-seize.

 

[High Wire]

Check your terminals for cracks between the post and the case.

 

[CharlieJ]

If the post/case joint has not been compromised, then the most probable cause is electrolyte deposited on the top of the battery during normal charging. Electrolyte is conductive so it needs to be removed. When I was maintaining my 12 x T-105 bank, after watering all 36 cells (ugh!); I would mix up baking soda and water and use a throwaway brush to brush the mixture on the battery top. I would keep brushing until the liquid stopped fizzing. Dry with paper towels and, Bob's your uncle, never had any corrosion form.

 

[C lectric]

If the corrosion is around only one terminal and reappears again soon after cleaning then the seal between the battery case and the post may have been compromised. ie. leaking.

Of course overcharging, overfillling of water, can make things worse but don't ignore damage.

This is USUALLY caused by ham handed techniques of cable terminal clamp removal.
If the clamps are tough to remove then you need a battery terminal puller. Otherwise there is a chance that any rough twisting or prying will damage the seal.

A decent puller should be available at a local auto parts shop.

 

[BILL GOOD1]

After rewiring? Did find the black plastic insulated wire to be corrosive. Eat all the tin from the tinned copper wire.

 

[Steve DAntonio]

Did you happen to take any photos? Localized corrosion at a terminal is often a result of a breach between the terminal and the case, allowing the battery to vent adjacent to the post. Looks closely here to see if there is a gap between the post and the case.

I'm partial to CRC HD Corrosion Inhibitor for coating terminals (after assembly), and Koper Shield on contact surfaces (applied before assembly). Everybody has their favorites...

In Taiwan