Corrosion on battery terminal



I have a Lexus 1995 ES300. For the past two months I have had corrosion build up on the red (+) terminal. The corrosion builds up every couple weeks and then the car does not start. I brush off the terminal with a steel wire brush every couple weeks and it is okay for a short time. The battery is less than a year old. Dealer says it is probably a bad starter, but I’m skeptical. Any other ideas?


If the terminals are tight, I would clean off with a baking soda solution, dry them and coat them with vasoline. That normally would fix the problem. I’ve never heard of a bad STARTER causing battery terminal corrosion!

You should also get a good second opinion from an actual mechanic.


I second all of Doc’s recommendations.

Just one proviso–If the battery is one with removeable caps, be sure that the baking soda/water solution does not get into the battery’s cells. That would give you more problems than you already have.

Conservative/careful use of baking soda & water, followed by drying and then coating the terminals with Vasoline should resolve the problem.


A too-high charging rate (above 15 volts) will cause the battery to produce more sulfuric acid fumes. These fumes combine with the lead of the battery post and make the corrosion. The corrosion isn’t a good electrical conductor. A crack in the battery case can allow the fumes to escape, also.
The charging voltage will be too high if the alternator output voltage is too high. The output voltage is controlled by a regulator in the alternator, or external to it.
Have the battery charging rate checked.


In addition to the comments from others, there is a seal surrounding the battery post where it enters the battery. If any previous person applied too much force to the terminal when removing or replacing the battery cable, the seal can become compromised. A compromised seal will allow moisture from the battery to seep up cause accelerated corrosion on the terminal.

If that happens, I’ve found that those felt red/green battery terminal pads can help slow down the corrosion.


Rapid post corrosion usually means a poor or failed post seal, allowing acid to seep up into the terminal. This is VERY common with flooded lead-acid batteries. It is VERY difficult to achieve a seal between plastic and lead…

You might try removing the terminal, cleaning it in a strong baking soda solution, clean the battery post, apply some grease around the post-case seal, install a pair of those red/green felt post protectors, and reinstall the connector. Spray the whole thing with silicone spray lube or “battery connector protective coating”…

The service morons suggestion at the dealership that you might need a new starter is ample reason NEVER to take your car there again…


Super glue a penny within an inch of each battery terminal and wipe the snow off of them regularly. It really does work.


See if you can swivel the terminal. If you can, the terminal has to be removed, cleaned where it grips the battery terminal and put on tighter. Just brushing it off won’t help fix the problem.

If it can’t be tightened, the cable can be replaced. The terminal still needs a proper cleaning if you want to try to prevent the buildup of residue.


There is no way in hades a bad starter will cause corrosion on your battery terminals.

If your car will not start, it means the corrosion is getting between the connector and the posts.

The posts need to be trued with a post tool and the connectors trued with a reamer. Then when clamped tightly, it will not allow corrosive fluids to get in between the post and connector.


I had the same problem and found a hairline crack next to the terminal causing acid to leak out.