Noxious fumes

Could anyone please tell me what is happening when I place steel
into my PHdown pickle pot to purposely copper plate sterling (or
solder on copper).The pickle fizzes around the steel (an old pair of
pliers) and creates noxious fumes. Of course, when I remove the
pliers, the reaction stops. Whatgas is being created? Many thanks for
all the wonderful help I receive.

Denny Diamond (from Freezing Toronto)

What gas is being created?

Hydrogen with perhaps a whiff of H2SO4

Jenifer Gow