The terminals are just blobs of green crumbly rusty goo.
I dont know how difficult this is to do on a 610, but we used to pour very hot water over the entire battery when this happened, then all that yuck will miraculously disappear..... at least then you will be working on a clean battery.......
However great care must be taken to avoid being scalded
It also has the effect of washing all the acidic yuck away from the battery case, which will stop further acidic corrosion, but any bare metal should be treated swiftly as a matter of course.
1990 GTA Atmo, 2003 Jaguar X type 2.5SE Auto, 2018 Kia Picanto GT-Line-S 1.25