Battery Terminal/s Black

[Dinty]

G'day All, I have had a look at Google Wiki etc to try and find the answer to this problem, with no luck I might add.
I have 7 restored Series Land Rovers, which I remove the batteries from them, mainly for security/fire risk reasons, what I've noticed is with some of them is the + Pos terminal is Black and looks as though it has been veneered, it does come off with a wire brush, any ideas as to why this happens, or are some of my 'SuperCharge' batteries stuffed (they ain't that old either) anyway any help appreciatted cheers Dennis:angel:

[Hoodoo Brown]

Oxidation of the Pos post. In that it is a lead composite alloy. The negative post does not oxidise as much as it should be pure lead in order to allow an electron flow.

The oxidation will grow back, also the pos post grows in size with age due to a secondary cell reaction, usually unseen on an automotive battery, due to the fact they don't last that long in comparative to a stationary battery, where it becomes a problem in a reduction of current capability.