The presence of corrosion indicates that battery acid has made it's way to the battery post and battery cable site. In a way, you could say this is somewhat normal only with respect to the fact that batteries often leak slightly at both posts due to how the battery is made (molded plastic encasing a metal post). The reason it is most often the positive post that corrodes to excess has to do with electrolytic action and polarity but that's all I will say as to the chemistry. I recommend removing both cables (REMOVE negative first and INSTALL negative last for safety and wear eye protection) from the battery. Remove the battery from machine. Clean the top of the battery with a spray-on battery cleaner. Clean the post with a hand held wire brush (brass is good, steel is OK). Rinse the battery with clear water and allow to dry thoroughly. Clean the terminal ends of the battery cables with the spray cleaner and wire brush. Wipe cable terminal ends dry with paper towel. I like to spray a heavy coating of "NO-CO-RODE" or similar battery terminal protectant spray on the battery posts, the battery around the posts, and the cable terminal ends as well (careful about that overspray, use old towels or such to mask what you don't want to paint with the spray). Buy a 2-pack of anti-corrosion felt washers at the auto parts store or wally world and put the red washer over the positive post & the green or black washer over the negative post. Re-attach your battery cables (positive first, negative last) You shold be good or better than new now.

Mownie has some good suggestions. Can anyone explain why this is the correct method to disconnect cables -(REMOVE negative first and INSTALL negative last for safety and wear eye protection)?

While I am not a battery expert, regular lead acid batteries develop corroded terminal because of off gasing. They are a real pain. The calcium batteries have a different construction and they are vented differently. No corrosion. Some of these are made by a company called East Penn - Private labels are put on the batteries. These are priced just a little higher than the batteries seen in stories like Auto Zone.

To Larry, if you diconnect the negative first you can't draw an arc if you accidentally hit the side of the mower/ or car with a wrench, because you are working on the grounded side. If you disconnect the positive lead first you will very likely draw an arc if you touch anything with the wrench. Drawing large arcs in the presence of battery gases, primarily Hydrogen is generally bad for your health.
steve

Steve has it right!

Precisely right! A+ grade for that answer. And the part about the off gassing is right, as one less obvious way way of getting some acid in contact with the battery posts. The reason for that is not so much the gas itself, but the fact that the battery vents are in the fill hole caps where acid is usually present from vibration and jostling during operation. As the gases make their way out of the caps through the vents, some acid will pass with it. I have also seen many a battery (mainly car and truck types w/round posts) that leaked around the post to top cover juncture so badly you could even "wiggle" the post and see acid come out there. I too prefer the "sealed top" maintenance free batteries. If you are wondering why the industry does not address the issue of the venting and leaking acid ruining all those cables and battery trays and hold down straps..........well....they have addressed it. They addressed it by helping their buddies in the parts business sell more cables, trays and hold down straps.

An easy way to keep this corosion under control without tools is to just wash the top of battery and both cables with a mix of baking soda and water. Note that the corrosion gets into the ends of the cables where the plastic outer coating has been stripped to add the battery clamps, and you want to get at that too to keep cable from breaking down. The baking soda almost instantly neutralizes the built-up mess and washes it away. Adding the felt washers does help keep it at much reduced levels. Good to use this mix to wash under the battery and any other metal in the immediate area to keep if from being effected by the same corrosive gasses.

My 2 cents worth.... Use caution when using baking soda for cleaning up corrosion. Posters are correct when stating it will neutralize the acid and clean up the mess. BUT some new batteries which have the fill holes, have these level with the top of the battery and not raised like batteries of old. As stated, soda neutralizes acid, and if it gets into the battery that's just what it will do to the acid in there also, which will kill the battery! My mother-in-law done this to her battery in her car cleaning it. Next morning it was dead and would never take a charge again.

Another idea for helping keep down corrosion... clean the battery as noted above or use some soap mixed up as you would to wash your car. Rinse it well and let it dry very well.

Then, try a trick my uncle taught me, that works VERY well. Before installing it again in your tractor (or other vehicle) get a small can of Permatex (or similar thick gooey gasket cement) and carefully coat around the bottom of the lead post also coating the plastic case surrounding the battery terminals (sealing the gap between the case and terminals). You might let this dry overnight if possible to let it get a bit more sticky, or being carefull you can put it back in right away. Be carefull reconnecting the cables so not to get the gooey stuff in between. Works GREAT and keeps corrosion down much better than the felt washers I've found out over the years. I do this on all my vehicles and yard tractor. No more corrosion woes.

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