Corrosion of battery contacts in all manner of things due to leakage from the batteries is a growing problem as we seem to accumulate more and more devices that contain batteries and it becomes a chore to replace batteries by their expiry date.
Replacing batteries by their expiry date does not guarantee freedom from leakage related corrosion. The battery market is flooded with counterfeit product and it is hard to know what is genuine, even from apparently reputable suppliers.
Above is a cheap Chinese digital caliper that was damaged by leakage from a brand name (Duracell) SR44 cell. The characteristic green residue has been cleaned from the positive contact with an alcohol soaked cotton bud, and then the contact scratched with a Burgeon 2834C fibre glass scratch brush (below) to remove remaining corrosion products whilst vacuuming to extract as much of the residue as possible. Again, a wipe with a clean alcohol soaked cotton but leaves the contact as clean as practicable. These scratch brushes are extremely effective, one needs to avoid over use which removes more plating than desirable.
Of course this operation does not deal with corrosion products under the contact, the life of the caliper is shortened. The operation is mostly about getting some more life from the thing.
A very thin smear of silicone grease applied to the contact reduces the risk of ongoing rust due to loss of plating material. Silicone grease has a high drop point and is fine even with the quite low contact pressure in the application, the sliding contact helps. Silicone grease should not be used on arcing contacts.
Above, the Burgeon 2834C fibre glass scratch brush is a pen like tool with a bundle of glass fibres, specifically designed for watchmakers to remove rust from watch parts. Product is available online for not much over $20, but they are quite probably Chinese clones though they seem to work quite well.