I have read that once ancient coins have been cleaned that some collectors coat the coins with Beeswax. Is this a common practise?
I would not call the use of beeswax to be a common practise today.
The majority of collectors who wax coins today use Renaissance Wax, which you will often see referred to as "
Ren Wax" on the internet. It's a micro-crystalline wax polish, made in
England, that is popular with museum conservators. The British Museum uses is on many artifacts, including
ancient coins. It dries quickly, does not leave finger prints,and will not damage
patina.
Waxing a coin can slightly change its appearance, giving it a dull sheen. For these reasons, the collecting community is divided on its use - a lot of people use it, a lot also do not. Realistically it will nto harm a coin and can be removed if preferred.
Most oftenly,
Ren Wax would be used on copper and copper
alloy coins like bronze,
orichalcum, etc. because it can
help prevent new corrosion. You don't often see it used on silver or
gold coins.